THE IMPACT OF STORM SURGE FROM SUCCESSIVE HURRICANES ON THE ALABAMA

BEACH MOUSE POPULATION

by

ALEXANDRA MARIE YURO

A THESIS

Submitted in partial fulfillment of the requirements for the degree of Master of Science in the Department of Geography

in the Graduate School of The University of Alabama

TUSCALOOSA, ALABAMA

2011

Copyright Alexandra Marie Yuro 2011

ALL RIGHTS RESERVED

ii

ABSTRACT

Global environmental change affects plants and animals by changing their

distributions and phenology, and altering ecosystem functions. Already endangered plants

and animals subject to these changes may be more vulnerable to extinction. It is important

to understand how species are likely to respond to environment change so that proper

steps can be taken to protect them in the future. This thesis observes the case of the

Alabama beach mouse (Peromyscus polionotus ammobates), a population endangered

initially because of habitat loss and fragmentation. The Alabama beach mouse population

likely will be negatively affected by environmental change through increased hurricane

frequency and intensity. Using Alabama beach mouse trapping data provided by the U.S.

Fish and Wildlife Service, I examined the storm surge effects of Hurricanes Ivan and

Katrina on mouse populations before, during, and after these hurricanes. Analysis of the

data was performed through contingency tables and Wilcoxon signed-rank tests. The

results of the analysis show that the Alabama beach mouse has the ability to survive

hurricanes in the future, if they are not successive. The Alabama beach mouse possesses

certain traits that make it more vulnerable to extinction in the near future by

environmental change, such as greater than normal disturbances both from humans (i.e.

habitat loss and fragmentation) and the natural environment (i.e. hurricanes and climate

change.) I postulate that the Alabama beach mouse population will be completely

iii

extirpated from Gulf Shores in the event of successive major hurricanes in the future. The

intended result of this study is not only to find out how the Alabama beach mouse may be

affected by global environmental change, but to contribute to the literature concerning the

species to be used in effective management strategies.

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LIST OF ABBREVIATIONS AND SYMBOLS

ABM Alabama beach mouse or Alabama beach mice

USFWS United States Fish and Wildlife Service

HCP Habitat Conservation Plan

CO2 Carbon dioxide

MSW Mobile Street West

NOS National Oceanic Service

NOAA National Oceanic and Atmospheric Association

IPCC International Panel on Climate Change

EPA Environmental Protection Agency

Z Z-score

km Kilometer

p Probability associated with the occurrence under the null hypothesis of a value as extreme as or more extreme than the observed value

< Less than

> Greater than

= Equal to

χ2 Chi-squared

v

ACKNOWLEDGEMENTS

First and foremost I would like to thank my dad for helping me get to where I am

today. He has always been proud of me for everything I do! I learned from him to just try

my best in all my endeavors, and from that lesson I think I will excel in life. Also, thank

you to him for proofreading for me all these years and adding the funny commentary to

make me laugh as I edit page after page.

I would like to thank Dr. Michael Steinberg for helping me through this entire

process. Many thanks for answering countless e-mails and helping me find a way to work

at my passion (animals, endangered species, and the beach mouse, of course) into the

larger field of physical geography. Special thanks should be awarded to Dr. Jason

Senkbeil for guiding me through the statistical analysis and allowing me to plague him

with a million questions. Also, thanks to Dr. Julia Cherry for being the biologist on my

committee and lending me her great expertise.

Lastly, I would like to thank the members at the Daphne office of the U.S. Fish and

Wildlife Service. Thanks to Drew Rollman for compiling my data and Carl Couret for

taking the time to sit down to discuss the beach mouse with me.

vi

CONTENTS

ABSTRACT ................................................................................................ ii

LIST OF ABBREVIATIONS AND SYMBOLS ...................................... iv

ACKNOWLEDGEMENTS .........................................................................v

LIST OF TABLES ................................................................................... viii

LIST OF FIGURES ................................................................................... ix

1. INTRODUCTION ...................................................................................1

2. LITERATURE REVIEW ........................................................................8

a. Extinctions and Biodiversity ....................................................................8

b. Coastal Development .............................................................................13

c. The Effects of Climate Change ..............................................................15

d. Hurricane Effects on ABM ....................................................................17

f. Increasing Hurricane Frequency and Intensity .......................................24

3. METHODOLOGY ................................................................................28

4. RESULTS ..............................................................................................33

a. General Trapping Analysis ....................................................................33

b. Statistical Analysis .................................................................................36

5. DISCUSSION ........................................................................................40

vii

a. Population Analysis ...............................................................................40

b. Factors that Hinder Beach Mouse Survival ...........................................44

c. Factors that Aid in Beach Mouse Survival ............................................49

6. CONCLUSIONS....................................................................................52

REFERENCES ..........................................................................................54

viii

LIST OF TABLES

4.1. Number of individual mice caught at each location ...........................34

4.2. Number of individual beach mice trapped at Laguna Key after extirpation of beach mice following hurricane Katrina .............................35

4.3. Descriptive statistics for Wilcoxon signed rank test. ..........................38

4.4 Ranks from Wilcoxon signed rank test ................................................38

4.5. Chi-square test for ABM trapping data ...............................................39

4.6. Chi-square contingency table results ..................................................39

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LIST OF FIGURES

1.1. Example of ABM habitat in Mobile Street West trapping area ............5

2.1. Ten-year history of land-falling hurricane tracks in Gulf of Mexico .19

2.2. Diagram of dune structure ..................................................................21

3.1 Partial map of Baldwin county showing the historic range of the ABM in Gulf Shores ............................................................................................29

4.1. Number of ABM trapped per season standardized by number of locations that trapped .................................................................................35

4.2. Standardized number of ABM trapped in spring seasons ...................36

4.3. The number of ABM trapped before versus after storms at all locations .....................................................................................................37

5.1. Image of ABM habitat within Martinique trapping area. ...................42

5.2. GoogleEarth image of trapping locations in Gulf Shores, AL ............44

5.3. GIS created map of ABM critical habitat/trapping locations .............45

5.4. Map of Gulf Shores showing Gulf State Park ....................................47

5.5. Gulf Shores storm surge map ..............................................................49

5.6. Map of Bon Secour National Wildlife Refuge ...................................50

x

1

CHAPTER 1

INTRODUCTION

Since humans have existed on earth, much of the decimation of animal and plant

populations has not been caused by direct human fault, but rather indirectly by destruction of

their environment. Before humans, endemic species lived symbiotically with their natural

environment, surviving and adapting to any negative variables associated with the habitat.

Plant and animal populations are at least partly adapted to their local selective environments

(Endler 1986; Rose & Lauder 1996; Schluter 2000), physically adjusting to survive with the

changes in the environment, such as climate, elevation, soil, and vegetation. As humans invaded

their habitat, many species could not acclimate to anthropogenic pressures. Consequently,

species have become more vulnerable to extinction due to human impact on the environment.

Many of the natural variables that species have learned to adapt to over time originate

from natural fluctuations in climate. Climatic variability shapes plant and animal communities,

and while most ecosystems can adapt to incremental changes in climate, larger changes

dramatically affect both flora and fauna. Generally, individual species do not respond to

approximate global averages, but rather to the changes that take place on a regional level

(Walther et al., 2002). There is a historical record of the effects of climatic change to global

systems, local ecosystems, and specific species. Although species have been subjected to

2

climatic changes throughout history, many species find it difficult to adapt at the current rate of

change under anthropogenic influences. This has led to imperiled statuses and even extinction.

As the number of imperiled species grows, biodiversity becomes threatened. Biodiversity

is the variety of life on earth, encompassing everything from abundance of genes and species to

whole ecosystems (Shah 2011). Biodiversity is important because it boosts ecosystem

productivity (Shah 2011). Healthy ecosystems have the ability to better withstand and recover

from a variety of disturbances. All species, big or small have an important role to play in

ecosystem productivity. The Alabama beach mouse (Peromyscus polionotus ammobates), the

species of topic in this thesis, is no exception. Peromyscus polionotus ammobates is a unique

species of mouse because it is known to inhabit only dunes and coastal forests, not buildings or

garbage dumps. The ABM diet consists largely of sea oat (Uniola paniculata) and gulf bluestem

(Schizachyrium maritimum), but also includes morning glory (Ipomoea sp.), seaside panicum

(Panicum amarum), camphorweed (Heterotheca subaxilaris), jointweed (polgonella gracillis),

sea rocket (Cakile constricta), and seaside pennywort (Hydrocotyle nonariensis) (USWFS 2009).

The Alabama beach mouse (ABM) and the dunes coexist as the beach mouse gathers and

redistributes the seeds of these plants that keep the dunes intact. In return, the mice are especially

reliant on the dune ecosystem because the dunes serve as a refuge from weather and predation.

Dunes are important in coastal ecosystems because they act as a physical barrier to the areas

further inland, protecting them from storm waves and erosion.

Changes in biodiversity caused by human alteration of the natural environment alter

ecosystem processes and the resilience of ecosystems to further environmental change (Chapin et

al. 2000). In order to prevent this, special attention should be paid to not only environmental

change, but also to specific species at risk. The ABM is one of these populations dwindling

3

because of changes to the natural characteristics of their habitat, increased human presence and

climate change. The United States Fish and Wildlife Service, hereafter referred to as the

USFWS, listed the ABM as endangered in 1985, initially due to destruction of their habitat by

human development. At that time, the USFWS estimated the entire population of remaining

beach mice occupied an area of 142 ha. (Neal and Crowder 2009,13). The Alabama beach

mouse’s distribution once ranged 53.9 km along the coastline in Baldwin County, from Fort

Morgan Peninsula to Perdido Key, Florida (71 FR 5517). From 1921 to 1983, the beach mouse

lost approximately 62% of its habitat in Alabama (Holliman 1983, 347).

The ABM is a nocturnal rodent that lives in the protection of primary dunes, secondary

dunes, and scrub dunes (Figure 1.1). At present time, few areas exist where the mouse can

survive safely, mainly due to the human influence within their natural habitat. Interspecific

competition with hispid cotton rats (Sigmodon hispidus), predation, and increased

pedestrian/vehicular traffic in the mouse’s habitat reduce the populations of the ABM.

Anthropogenic disturbances such as artificial lighting and sand contaminated with gravel or

construction debris also pose threats to ABM existence. The Alabama beach mouse is semi-

fossorial, making distinct burrows underground the sand filled with dried grasses in which to

nest. These burrows are dug into the sloping sides of sand dunes and consist of three main parts.

The important aspect of their burrows in that a mouse can quickly pop open a plug of sand and

escape if threatened or disturbed (fws.gov/daphne). Artificial lighting influences beach mouse

survival by increasing their risk of predation. The ABM avoids foraging in well-lit areas to avoid

predation, and may therefore spend more time away from areas with food resources. They are

unable to utilize this habitat as often as they had in the past (71 FR 5523). ABM exhibit a pure

white underside, and dark brown dorsal stripes are common. This coloring allows the ABM to

4

camouflage into the light-colored sand, because the mouse’s long list of predators includes the

red fox (Vulpes vulpes), coyote (Canis latrans), great horned owl (Bubo virginianus), great blue

heron (Ardea herodias), weasel (Mustela nivalis), striped skunk (Mephitis mephitis), raccoon

(Procyon lotor), and various snakes (Blair 1951, Bowen 1968, Holler 1992, Novak 1997, Moyers

et al. 1999, Van Zant and Wooten 2003). Predation is not a major limiting factor for ABM that

have sufficient habitat and recruitment, but this has become a concern after hurricanes when

predators and the beach mouse are more concentrated in smaller, isolated habitat patches

(USWFS 2009). Feral and free-roaming cats are non-native predators to the ABM, and were one

of the main causes of extirpation of a population of ABM at Ono Island (Holliman 1983).

Several of these species are attracted to human refuse, another negative effect of human presence

in the area (USFWS 2009).

There are several different estimated areas of beach mouse habitat, but most are

approximately 991.5 ha (3.8 square miles), with 60% or 625.6 ha (2.4 square miles) of this area

currently on public land (USFWS 2009, 4). Within a home range of 0.4 to 0.69 ha, a

monogamous pair of beach mice use up to 15-20 burrows each (Neal and Crowder 2009, 12).

At this time, there is one metapopulation divided into two local subpopulations by the most

recent storms, Gustav and Ike; however USFWS believes these populations to be sustainable

(USFWS 2009). The USFWS finds it hard to estimate exact population numbers for the ABM

because of seasonal fluctuations and tropical cyclone occurrence, and is therefore only able to

generate large population estimates through trapping data. As a result, the USFWS considers

available habitat, not estimated population, the most influential factor in assessing the overall

condition of the beach mouse species (Neal and Crowder 2009).

5

Figure 1.1. Example of ABM habitat in Mobile Street West trapping area

Since the mouse’s historic distribution was relatively small, the continuing

development of the Alabama coastline threatens the mouse with extinction. Today, human

presence, tropical cyclones, and interspecific species competition continue to shrink and destroy

the mouse’s habitat. By examining the case of the ABM, this thesis demonstrates how human

alteration of coastal areas and global climate change has a direct impact on animal species.

Laws have been implemented in order to protect the beach mouse; however, there are

many obstacles to effective conservation such as:

...a lack of information, a tendency to ignore a problem until it becomes a crisis, a

failure to commit to adequate resources, and a failure to reward landowners who aid in

the restoration of imperiled wildlife and given the steadily increasing population and

growing economy of the [sic] United States. (Wilcove 1999, 235)

These obstacles make protecting the beach mouse and most imperiled species exceptionally

difficult. According to the USFWS, the degree of threat to the persistence of the beach mouse

remains high, and economic conflicts hinder the species recovery (USFWS 2009).

6

In the past, adaptation of coastal communities to climate change mainly focused on

protecting infrastructure rather than coastal habitat and biodiversity. It is imperative, therefore, to

contribute to the body of literature on conservation in order to help people understand the

negative impact of humans on the Alabama beach mouse’s habitat and population, as well as

potential reductions in the beach mouse’s viability as a result of global environmental change.

One potential consequence of global climate change is the increase of hurricane frequency and/or

intensity. ABM habitat remains under severe threat from further habitat fragmentation combined

with the probable increase of hurricane impacts, such as storm surge and high velocity winds.

Even if hurricane intensity and frequency do not increase, sea level rise will result in increased

storm surge; areas previously thought to be outside of contemporary storm surge zones could be

exposed to future hurricane damage (Frazier et al. 2008 and 2009, Kleinosky et al. 2007, Wu et

al. 2002). These changes could potentially alter and destroy available ABM habitat. It is

important, therefore, that further studies be performed in order to understand the future of this

species and to work to protect it.

Researchers of the ABM suggest that hurricane disturbance is a large issue in the future

of the beach mouse’s viability. Natural disturbance events are unavoidable, and with the

possibility of hurricanes becoming more frequent in the near future due to global climate

change, this thesis examines how the beach mice may be affected. Obtaining knowledge of how

species are expected to respond to climate change is essential if we are to create effective

management strategies to help species adapt in the future. The goals of this thesis are to answer

the following questions: 1.) How did Ivan and Katrina, two sequential major hurricanes, affect

populations of Alabama beach mice at specific trapping locations? 2.) With the threat of

enhanced tropical cyclone frequency or intensity due to global climate change, what is the

7

estimated influence of these potential cyclones on the future of the ABM population in Gulf

Shores, AL?

8

CHAPTER 2

LITERATURE REVIEW

Extinctions and Biodiversity

Plant and animal extinctions have naturally occurred throughout their existence as a result

of variations and disturbance in the natural environment. Since humans have been on earth, the

sheer intensity of human population growth has threatened plant and animal species. Men

reconfigured the landscape as they stopped being nomadic hunters and modified the natural

environment to suit their needs (Isenberg 2000). By changing biogeochemical cycles, land use

and atmospheric composition, humans completely altered the global environment. A classic

example is the major die-off of megafuana in Australia, North America, Madagascar and New

Zealand within just a few centuries. In these environments, the extinction of large mammals and

flightless birds corresponds with human invasion. Comparatively, extinction rates were slower

and smaller in Africa, where humans evolved longer with the megafauna (Wilson 1992). There

the animals had more time to adjust, unlike the animals at other locations which had to adapt to

the sudden arrival of humans. Furthermore, there is substantial evidence that extinction has been

accelerating over the last 500 years due to human impact, including the advent of weapons of

mass destruction, industrial poisons, pharmaceuticals, and human wastes (Levy and Sidel 2009,

McKee 2009, Tonn 2009).

9

Despite the appearance that humans are solely responsible for pushing many species to

extinction, most of these imperiled species already existed in environments subjected to

catastrophic events and other environmental stressors. A familiar case in point is the destruction

of the bison species in the Great Plains. This environment was unforgiving, originally

threatening the natural mortality of the population through resource competition, drought, and

fire. When Euroamericans introduced the horse, Old World diseases, and fur trade into the Great

Plains, the bison was consequently pushed to the brink of extinction (Isenburg 2000). Similar

situations have happened repeatedly throughout time as humans continue to put pressure on

ecosystems. On the other hand, although the destruction of the bison was partially a result of

unsustainable exploitation of natural resources, humans are not exclusively responsible for this

environmental catastrophe nor many others.

For many species it is not only the environment that shapes their population, but

phenotypic variation among individuals. Having certain traits such as narrow geographic range,

limited dispersal capacity, low reproductive output and a high degree of habitat specialization

can render them more vulnerable to environmental disruptions (Isaac et al. 2009). Possessing

these qualities typically increases the chance that a species will be more sensitive to

environmental change in the future. Combined with habitat fragmentation and destruction,

invasive species, and overexploitation, climate change can accelerate the rate of species

extinction (Thomas et al. 2004a, Brook et al. 2008, Dunn et al. 2009). As plant and animal

distributions change under the new climatic regime, fragmented habitats, which may become

climatically suitable with future warming, may be too remote from current distributions and

beyond the dispersal capacity of many species (Walther et al. 2002). A species, such as the

ABM, whose habitat is already restricted by habitat fragmentation and whose population is

10

isolated, is also more susceptible to losses in genetic diversity (Isaac et al. 2009, Williams et al.

2008). A combination of phenotypes, environment and human presence gives species the ability

to withstand environmental disturbance and can aid in their development during global

environmental change.

To preserve the species that are left, conservationists and other decision makers must

monitor past and present human behaviors and propose and implement changes to decrease the

chances that vulnerable species will be pushed to extinction. Fortunately, there is an increasing

knowledge and use of environmental history in conservation (Foster 2000). Scientists are also

becoming more aware of the impacts of human cultures on nature, and fundamental shifts have

occurred in scientific thinking about anthropogenic influences. Only twenty years ago, many

environmental ignored the human influences on ecosystems; however, at the present time it is

impossible to overlook the human history of land-use because “few landscapes lack human

legacies” (Foster 2000, 7).

In response to human-induced changes in the environment, biodiversity is changing at

an unprecedented rate (Pimm et al. 1995, Sala et al. 2000, Thuiller et al. 2005). Habitat

fragmentation and disturbance by anthropogenic factors affects diversity and abundance of

species worldwide (Tilman et al. 2001, Fahrig 2003, Ewers and Didham 2006, Krauss et al.

2010). Biologist E.O. Wilson (1992, 253) speaks of the “four mindless horsemen of the

environmental apocalypse”: overexploitation, habitat destruction, introduction of alien species,

and the diseases that they carry, all four of these factors are human-induced. Due to human

alteration of the natural environment, earth is now entering the sixth event of major extinctions

(Chapin et al. 2000). The consequences of human impact on the environment need to be

acknowledged before humans push more species to extinction.

11

With the number of imperiled species on the rise due to habitat destruction and climate

change, scientists are obtaining knowledge on local extinction processes(May 2010, Svenning

and Condit 2008, Thomas et al. 2004). Individual species’ response to climate change may

disrupt their interactions with others at the same or adjacent trophic levels (Walther et al. 2002).

Just one species’ extinction can lead to the demise of others, with consequences that arise from a

species’ removal having the potential to cause a cascade of other events with unanticipated

consequences (Wilcove 1999). Many studies have examined threats to imperiled species, and

habitat destruction and degradation consistently rank among the top contributors to species

endangerment. Wilcove et al. (1998) found that of the 1,880 imperiled species analyzed, 85% of

the species were affected by habitat destruction and degradation. Habitat loss is the primary

threat to biodiversity (Ewers and Didham 2006, Sax and Gaines 2003, Thomas et al. 2004).

Human invasion into natural areas decreases habitat size, and as a result, species richness is

reduced with only generalists and a few specialists inhabiting these areas (Honnay et al. 1999,

Godefroid and Koedam 2003).

Habitat loss and fragmentation also reduce a species’ population size, which increases

the probability of extinction from demographic and/or environmental stochasticity (Griffen and

Drake 2008, Lande et al. 2003, Desharnais et al. 2006). Even without further habitat loss,

species in already fragmented habitats may become extinct (Krauss et al. 2010). This occurs

through a process called “extinction debt” in which declining species may survive a while, but

are in a deterministic path to extinction if they live within destructed, fragmented habitats

(Tilman et al 1994, Kuussaari et al 2009). The negative effect of habitat patches of decreasing

habitat size and increasing isolation on species have been well documented in the literature, cf.

Dodd (1990), Griffen and Drake (2008), and Hunter (2002). For example, Patten et al. (2005)

12

studied the effects of habitat fragmentation on the abundance of prairie chicken. They found

that extinction risk increased as the chicken’s habitat size was reduced. The underlying theory is

that larger habitats can support more species and higher carrying capacities (Patten et al. 2005).

Degradation of the natural environment by human activity is certainly not a new

occurrence, but rapid and global scale at which change is now taking place is a cause of concern

(Lunney 1991 and Houghton 1994). Brown and Laband (2006) analyzed the relationship of

human activity on species imperilment and found that the rising levels of human development

(number of people, roads, and intensity of nighttime lights) significantly correlated with the

imperilment of species. Their models showed that a 1% increase in level of human activity in the

United States was associated with an approximately 0.25% increase of endemic species at risk of

extinction. They also concluded that a diffuse or concentrated distribution of human activity did

not have a significant effect on species imperilment; the proportion of species imperiled in an

area was not affected by the amount of human activity within that area. Their major findings

were in agreement with Wilson: human activity is the most relevant anthropogenic factor

explaining loss in biodiversity.

The loss of structural connectivity, for example having corridors of unbroken habitat for

animal movement from one area to another, also plays a large role in the decline of many species

(Bennett 1990). Bennett (1990) documented the use and value of habitat corridors in fragmented

habitats for the dispersal and gene flow of small mammals. Protecting or acquiring areas for

habitat connectivity is a challenge for conservationists because management does not usually

begin until after landscape is already fragmented (Barrows et al. 2011). Urban, residential and

agriculture development separate areas of habitat between which species were once able to move

through. This restricts them from their normal daily or seasonal migratory patterns (Bennett

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1900). Barrows et al. (2011) highlighted the importance of corridors for the Palm Springs pocket

mouse (Perognathus longimembris bangsi). Just like the ABM, the pocket mouse was red-listed

due to habitat degradation and fragmentation, and maintaining corridors is vital in sustaining

multi-generational populations (Barrow et al 2011). Habitat connectivity is equally important for

ABM, especially those in fragmented habitats lacking certain habitat types (i.e. scrub habitat).

Beach mice need access to other types of habitat when food or burrow sites become scarce in the

frontal dunes (USFWS 2009).

Coastal Development

In addition to anthropogenic contributions to global climate change, humans have caused

a direct decline in native coastal species by settling along coastlines. Coastlines are especially

attractive for human settlement. With 53% of the world’s population living within 80.5 km of the

coastline, this development places great stress on coastal environments (Woods and Poole,

NOAA 2011). Between 1970 and 2011, population in U.S. coastal counties increased by 43%

(Woods and Poole, NOAA 2011). This growth continues apace, with population in coastal

counties expected to increase by 13.6 million, or 8%, by 2020

(http://stateofthecoast.noaa.gov/population/welcome.html). The NOAA assessed coastal

population data (Woods and Poole 2010), finding that from 1987-2013 there was a 96.96%

absolute population increase.

14

The Southeast and Gulf Coast regions are increasingly a destination for job seekers and

retirees, supporting the highest number of migration by humans (Crossett 2004). Zhang and

Leatherman (2011) used Census data to find how barrier island populations increased between

the years 1990 and 2000. In Alabama, the permanent population grew from 7,336 in 1990 to

11,376 in 2000, resulting in a 55% population change (Zhang and Leatherman 2011, 360).

Population density increased from 51 humans/km2 to 80 humans/km2 (Zhang and Leatherman

2011, 360). They also predict that the population of Baldwin county, Alabama will increase

from the 2009 population of 180,000 to 262,000 by 2030

(http://stateofthecoast.noaa.gov/population/welcome.html). It is important to consider that

Alabama has a relatively small coastline of 85.3 km (Beaver 2006). Compared to other states

bordering water, Alabama’s coastline ranks only 18th out of 23 (Beaver 2006). Also, these

statistics only include permanent residents; the numbers do not emphasize the likely concomitant

increase in the number of tourists.

Development of the Gulf Coast greatly boosts the economic growth of the region, but the

high density of people and industry is also a potential threat to the ecological condition of the

Gulf’s coastal environment (EPA 2001). Human alteration and fragmentation of habitats, most

often a result of increased development through urbanization or farming, is the leading cause of

extinction of species (Ehrlich et al. 1980). In North America, humans have spent the last 250

years altering the natural landscape to suit their needs. Even today, as development along

coastlines continues, the number of imperiled species grows as well. Along the Gulf Coast, the

ABM is just one of many endangered and threatened species that is vulnerable because of

environmental stressors and human presence. In Baldwin County, Alabama alone, the list

includes a number of species in the sea turtle genus (Chelonia), the wood stork (Mycteria

15

americana), southern clubshell (Pleurobema decisum), Alabama sturgeon (Scaphirhynchus

suttkusi), Perdido Key beach mouse (Peromyscus polionotus trissyllepsis), and the West Indian

manatee (Trichechus manatus) (USFWS 2011).

The Effects of Climate Change

Humans not only reduce animal and plant populations by habitat destruction, but also

through human-induced changes to the environment. Sala et al. (2000) reported that land use and

climate change will have the largest relative effect on biodiversity. Humans have contributed to

climate warming by increasing concentrations of greenhouse gases in the atmosphere.

Anthropogenic influences are likely to cause the most rapid climate change that Earth has

experienced in the past 18,000 years since the end of the last glaciation (Chapin et al. 2000).

Anthropogenic climate change over the past thirty years has caused multiple ecological

responses (McLaughlin et al. 2002, Parmesan and Yohe 2003, Parmesan 2006, Root et al. 2003,

Rosenzweig et al. 2008, Walther et al. 2002). Because the earth is presently warmer than it has

been at any point in the past 1-40 millions of years (Houghton 2001), this climate change has the

potential cause for species’ extinctions. Based on climate projections by the IPCC, Thomas et al.

(2004) predicted extinction possibilities for 20% of the earth’s terrestrial surface, finding the

numbers of species in danger of extinction because of changed distributions of species. At the

16

lowest climate-warming scenarios, the authors reported that 18% of the 1,103 plant and animals

species in the study group were subject to extinction in the future (147). For species that have no

method of dispersal under future climate change (i.e. are already fragmented), mammals have the

highest projected extinction percentages (24% under minimum expected climate change)

(Thomas et al. 2004, 146).

Abrupt climate change has occurred in the past for many reasons, but it is conceivable

that human forcing of climate change is increasing the probability of large, abrupt events (Alley

et al. 2003). With humans introducing more CO2 into the atmosphere, the greenhouse effect is

increased. This results in higher mean global temperatures, which causes shifts in the

geographical distributions of organisms (Malcom et al. 2002, Pearson et al. 2002 and Moritz et

al. 2010). In the past, climate change resulted in glacial retreat; however, today’s warming trend

is expected to occur at a much higher rate than before, with significant implications for

ecosystems. Some effects of global climate change on species include altered phenology of

flowering (Menzel et al. 2006, Root et al. 2003), breeding and migration (Walther et al. 2002)

and changing species distribution patterns (Walther et al. 2002, Svenning and Condit 2008). In

addition, shifts in biogeography include the movement of invasive species from adjacent areas

where they affect native species (Walther et al. 2002). Global climate change may also result in

changes such as increasing sea surface temperatures and water vapor caused by thermal

expansion of the warming oceans (Emanuel 2005, Trenberth et al. 2005, Webster et al. 2005),

shrinking glaciers (Dyurgerov and Meier 2005, Oerlemans 2005) and melting permafrost

(Frauenfeld et al. 2004, Yoshikawa and Hinzman 2003). Precipitation is expected to decrease

30% in summer precipitation and increase 25% in spring (Mearns et al. 2003). It is well

documented that climate change also will have considerable impacts in coastal regions (Bardsley

17

2006, Caton 2007). These impacts include sea level rise (Frazier et al. 2008 and 2009, Kleinosky

et al. 2007, Wu et al. 2002), increasing coastal erosion (Beualieu and Allard 2003, Forbes et al.

2004b, Orviku et al. 2003) and flooding, more extreme weather events, and changes to run-off

patterns (Caton 2007). The already vulnerable ABM population is in particular danger of

extinction from these coastal environmental changes alone.

As previously mentioned, climate change is expected to alter distribution and abundance

of many species. Root et al. (2003) found numerous “fingerprints,” or temperature-related shifts

due to global warming, that affect species. The authors used multiple statistical techniques to

find statistically significant changes in species by examining 143 studies containing 694 species

or groups of species affected by global warming in the past fifty years. Through this meta-

analysis of results, evidence suggests that scientists have found that significant impacts of global

warming are already discernible in many plant and animal species on a large-scale and long-term

basis. The majority of predictions of climate change induced extinctions focus on geographical

shifts or altered phenology. My thesis is unique within this body of literature, because it seems to

be the only study that examines how an animal species will be affected by hurricanes through

climate change.

Hurricane Effects on ABM

There is a growing body of literature projecting how species will be affected by global

climate change; this thesis contributes to the larger body of literature by examining increasing

18

hurricane frequency on the ABM. Although humans are primarily responsible for the initial

destruction of the habitat and decimation of the ABM population, the influence of tropical

cyclones also affects the beach mouse’s long term survival and recovery. Hurricanes can

adversely affect the ABM in a variety of ways including direct mortality of individuals or

relocation/dispersal, alteration of habitat and vegetation and modification of predator/competitor

relationships (USFWS 2009).

Since the ABM was listed as endangered in 1985, multiple tropical cyclones have struck

the east northern Gulf Coast (Figure 2.1), altering beach mouse habitat and reducing population

numbers. Because hurricanes are stochastic events, there may be a number of destructive storms

one year and then none the next. From 1986 to 1994, tropical cyclone activity was minimal in the

Gulf Shores area. 1995 was a destructive hurricane season though, with both Hurricane Opal and

Erin moving inland close to Gulf Shores. Hurricane Opal was a Category 3, and provided

researchers of the ABM an opportunity to study the effects of major tropical cyclones on ABM

habitat. In 1997, Hurricane Danny passed directly over Fort Morgan, leaving 101 cm of rain in

its slow-moving path. In 1998, Georges made landfall slightly to the west of Gulf Shores,

resulting in a 3.7 m storm surge in Fort Morgan. The following seasons were relatively quiet

until 2004, when Category 3 Hurricane Ivan made direct landfall in Gulf Shores, causing 3-4.6

meter storm surges. Ivan was the strongest storm to hit the area in 25 years, and again provided

scientists research opportunities for post-hurricane beach mouse data. In hurricane history, the

year 2005 is known as the most active season on record, with twenty-six named tropical storms,

and seven major hurricanes (NOAA 2009). Even though Hurricane Katrina (2005) made landfall

just east of New Orleans, the resultant storm surge in Mobile Bay was 3.7 meters. In the same

year, Dennis brought tropical storm force conditions to the Gulf Shores area. In summation, the

19

impact of these storms on the ABM habitat and population was abnormal for such a short time

period.

Figure 2.1. Ten-year history of land-falling hurricane tracks in east northern Gulf of Mexico

(http://www.wkrg.com/weather/article_education/mobile_hurricane_history/4083/)

The tropical cyclones that hit the Gulf Coast during the 2004-2005 hurricane seasons

especially affected the ABM’s habitat. These disturbance events served as evidence that back-to-

back hurricanes may severely damage their habitat to a point where the beach mouse might not

be able to recover from future stochastic events. Although disturbance is accepted by ecologists

and conservationists as an important component in natural ecosystems (Hobbs and Huenneke

1992) large or frequent disturbance events can cause major changes in structure within an

ecosystem. For the case of the ABM, hurricane disturbance is beneficial in breaking up

population subgroups and force population mixing (Wooten and Holler 1999), but the negative

20

effects of ecological disturbance mechanisms (hurricanes) have been increased by anthropogenic

disturbance mechanisms such as habitat destruction/fragmentation and artificial lighting.

Habitat recovery time depends on multiple factors such as severity of hurricanes, habitat

elevation, and post-hurricane recovery efforts and because each storm area is unique, these

recovery times can take anywhere from 1 to 40 years (Johnson 1997, Boyd et al. 2004, Traylor-

Holzer et al. 2005). Oli et al. (2001) modeled the probability of extinction of the ABM using

population viability analyses, or PVA. Without catastrophic disturbance, the species only had a

0.2% probability of becoming extinct in the next five years. In the presence of disturbance,

using data collected post-Hurricane Opal, the probability of extinction rises to 48% for the beach

mouse (Oli et al. 2001).

There have been several studies attempting to quantify the effects of hurricanes on

beach mouse habitat and corresponding mouse populations after hurricane events. Larger

numbers of mice were consistently captured post-hurricane in the transition dunes, possibly

indicating that they use these areas as refuge (see Figure 2.2). Later, as the frontal dunes’

vegetation recovers, the mice rapidly reoccupy these areas. Within their critical habitat, there

are few areas where the mouse has a corridor to move safely between the frontal dunes and

higher elevation scrub habitat above the storm surge inundation level. Often these areas are

densely populated with human development and traffic, or contain large open spaces in which

the beach mouse would be susceptible to predation. While preservation efforts put forth by the

USFWS help to keep the ABM population viable, unpredictable hurricanes can still threaten

their numbers.

21

Figure 2.2. Diagram of dune structure

The first study to analyze the population dynamics of ABM post-hurricane was Rave

and Holler (1992), seventeen months after Hurricane Elena. Extensive damage to the dunes

from Hurricane Elena was still evident when trapping took place over three years from 1987 to

1989. Rave and Holler found that mean minimum number of ABM known alive ranged from

32.9 in 1987 to 77.5 in 1989. While year-to-site numbers of beach mice trapped did not differ,

the numbers differed seasonally. The study also demonstrated that although the population of

beach mice was low to begin with, the numbers increased significantly over the three year

period while recovering from the effects of Hurricane Elena. Despite natural barriers (i.e. dunes,

barrier islands, wetlands), tropical cyclones can still have a devastating impact, which may be

further exacerbated by anthropogenic factors such as residential or commercial development.

Swilling et al. (1998) studied the population dynamics of the ABM following

Hurricane Opal, which made landfall 100 km east of study sites at Bon Secour in Gulf Shores.

The hurricane resulted in storm surges three to four meters above normal, and ABM habitats

suffered catastrophic damage due to salt-water inundation and primary dune destruction. Mouse

populations fell approximately 15-20% as the direct result of the hurricane (Swilling et al.

22

1998). Beach mouse habitats can suffer catastrophic damages when water inundates burrows

and foraging areas by over-washing primary dunes and leaving pools of water in the secondary

dune area (Swilling et al. 1998). These effects therefore alter the beach mouse habitat and

population and reduce available food sources for the mice. ABM habitat consists of mainly of

frontal dunes, but during storms the mice move further inland to the transition area (Swilling et

al. 1998). Previously, beach mice were thought to reside only within the frontal dune area, but it

is now understood that the ABM exists in almost all types of habitat within the coastal area,

with the exception of maritime forest, inundated areas and wet beach (Farris 2003, Neal 2003).

ABM distribution also changed within the study area following Hurricane Opal.

Approximately 47% of the ABM originally trapped in their usual beach habitat migrated to the

“scrub/transition” dunes, others increased their foraging time there, and continued to use them

in the following seasons. Swilling et al. (1998) also documented the migration of one female

radio-collared mouse that originally resided in the frontal dunes but rapidly constructed a new

burrow within the secondary dunes immediately following the storm. ABM continued to utilize

these distinct areas until April 2006, until regrowth of vegetation occurred in the primary dune

habitat. Although the hurricane was highly destructive to ABM habitat, trappings post-hurricane

were not significantly different than numbers caught under natural annual climatic cycles.

Generally, ABM numbers decrease during the spring and summer months. Population

continued to increase as the mice entered the autumn/winter season of maximum reproduction,

but the April 1996 population was 22.3% lower than the April 1995 estimates (Swilling et al.

1998). Consequently, although the immediate changes in population following the storm were

not significant, the long-term changes seven to ten months after the storm were much more

significant. Studying the effects of hurricanes on population dynamics has proven beneficial to

23

beach mice because it has changed previous beliefs that the most crucial habitat for beach mice

was the frontal dunes. This study changed the policy on what defines ABM critical habitat

(Swilling et al. 1998), adding to areas high above the mean tide line, or 152 m, to also include

the scrub/transition habitats (72 FR 4329). Critical habitat is defined in the Endangered Species

Act (1973) and simply refers to the specific areas within the geographical area occupied by a

species at the time is becomes listed, but may later designate other areas as more research takes

place (71 FR 5519).

Pries et al. (2009) studied the effects of Hurricane Ivan on the dunes and documented

changes in their occupancy by Santa Rosa beach mice (P. p. leucocephalus), the only unlisted

sub-species of Peromyscus polionotus remaining. Hurricane Opal had already fragmented the

frontal dune system; as a result, when Ivan came through, the 68% loss of frontal dunes and

14.8% loss of scrub dune habitat in the study area had a large impact. This study also showed a

substantially lower occupation of the frontal dunes by beach mice following hurricane activity.

The authors hypothesized that the lower occupancy could be a result of either a reduction in

population size or the movement by the beach mice to scrub habitat, although an increase in use

of the scrub habitat was not recorded post-hurricane. One thing to note is that this study area is

slightly different from the ABM habitat, as the frontal and scrub dune areas are separated by

swales that flood, preventing movement of the mice during hurricanes (Pries et al. 2009).

Nevertheless, the study is significant in showing that the existence of multiple habitats is

important to multiple beach mice species.

Other post-hurricane studies were performed through habitat surveys conducted by the

USFWS after Hurricanes Ivan and Katrina. These surveys indicated that damage occurred to

ABM habitat from torm surge and wind-driven salt/sand spray. These two hurricanes eliminated

24

or severely damaged about 90-95% of the primary and secondary dune system as well as an

undetermined amount of tertiary dune and scrub dune habitat (USFWS 2004 and 2005a). As the

frontal dunes are destroyed, they lose their buffering capabilities, exposing the scrub, and making

them more vulnerable to future storm damage. More recently, destruction to Alabama beach

mouse habitats occurred when Category 2 Hurricanes Gustav and Ike hit the coast in 2008,

fortunately damaging only less than 10% of the habitat range (Darren LeBlanc per. comm.;

unreferenced 2008). In 2009, the USFWS stated that ABM habitat continues to struggle with

recovery from the devastating effects of the 2004 and 2005 hurricane seasons and storm surge

impacts. The distribution of ABM across its range has been substantially reduced since the storm

events of 2004-2005 and will remain so until reintroductions can be made at Gulf State Park

(USFWS 2009, 21).

Increasing Hurricane Frequency and Intensity

The National Hurricane Center and Central Pacific Hurricane Center utilize the term

“major hurricane” for hurricanes that reach maximum sustained one-minute surface winds of at

least 96 knot (50 m/s, 111 mph); this is the equivalent of Category 3, 4, and 5 on the Saffir-

Simpson scale. Numerous studies have shown that compared to the long-term average, in the

past few decades there has been an increase in the number and proportion of major hurricanes

(Webster et al. 2005, Emanuel 2005, Goldenberg et al. 2001, Elsner et al. 2000). Experts

speculate that we have entered a naturally occurring period of increased major hurricane activity

25

that may be exacerbated by global climate change. From 1995 to 2000, there were twenty major

hurricanes, or 3.8 per year, while during the last active multi-decadal period from 1944 to 1970

the average number of major hurricanes was only 2.7 (Goldenberg et al. 2001). While major

hurricanes account for only 20% of tropical storm activity in the United States, they create 80%

of the total damage (Pielke 1998). Increases in key measures of Atlantic hurricane activity in

recent decades have been attributed to the roles of both natural climatic cycles and anthropogenic

factors, as we are beginning a new period of greater major hurricane activity (Elsner et al. 2000).

Natural atmospheric fluctuations such as El Niño/La Nina and the Atlantic Multidecadal

Oscillation (AMO) influence hurricane development or hindrance. For example, the last period

of lower level hurricane activity (1991-1994) coincided with the El Niño Southern Oscillation

(ENSO) and returned to higher levels under the positive phase of the AMO. When the AMO is

in its warm, or positive phase, Atlantic Basin SSTs are warmer, causing more tropical storms to

mature into hurricanes (NOAA). These natural teleconnections in the atmosphere occur on

interannual and multidecadal timelines that influence the variability of hurricane season activity.

The ideal conditions required for the formation of tropical cyclones include the

following: large open ocean with sea surface temperatures (SST) exceeding 26.7°C (80°F), a

moist atmosphere greater than 8 degrees north or south from the equator, weak vertical shear of

the horizontal winds, maximum sustained near-surface winds of 33 m/s (74 mph), and a pre-

existing low-level and/or upper-level disturbance (Elsner and Kara 1999). Tropical cyclones are

also fueled by water evaporating from warm oceans. Since the Industrial Revolution, humans

have contributed increasing amounts of carbon dioxide into the environment that traps heat in the

lower atmosphere. The results of human-induced global warming include worldwide

atmospheric and oceanic temperature increases and sea level rise. Higher SSTs decrease

26

atmospheric stability, which increases the penetration depth of a vortex and therefore making

developing tropical cyclones more resistant to vertical shear (DeMaria 1996). Thus, it seems

plausible that it is the combination of both natural cycles and global warming that causes

increased hurricane intensity. Intensity refers to the category of the storm, based on the strength

of the sustained winds. Emanuel, perhaps the most notable academic on the topic, concluded that

“the upturn in tropical mean surface temperature since 1975 has been generally ascribed to

global warming, suggesting that the upward trend in tropical cyclone [Power Dissipation Index]

PDI values is at least partially anthropogenic” (Emanuel 2005, 687).

Some scientists see the AMO and other natural atmospheric fluctuations as the only

influence on hurricane frequency and therefore think that there is no correlation between global

climate change and hurricanes. For example, Goldenburg et al. (2001, 476) stated that “Although

North Atlantic SSTs directly impact tropical cyclone activity as a local thermo-dynamic event, it

appears unlikely that this is their only physical link to hurricane activity.” Across the literature,

inconsistencies also exist with regard to the potential role of the AMO in tropical Atlantic

warming and hurricane activity (Mann and Emanuel, 2006). Pielke et al. (2005) explain the

increase in hurricane activity post-1995 by relating it solely to the natural and cyclical variability

of the AMO. Other meteorologists such as Donnelly and Woodruff (2007) argue that the modern

SST record is too short to infer a recent change in increased cyclonic activity because of climate

change. On the other hand, even skeptics agree that the possibility exists that the unprecedented

increase in activity since 1995 may be due not only to multi-decadal-scale changes in SSTs, but

also to the long-term temperature increase from global climate change (Goldenburg et al. 2001).

It is more plausible to assume that North Atlantic SST trends result from a combination of

background large-scale warming believed to be largely radiatively forced, and an internal AMO

27

signal that projects onto regional SST trends (Mann and Emanuel 2006). Meteorologists predict

that the current AMO phase will last until about 2015 or possibly 2030. Over time this

information will be helpful in identifying whether or not global warming is partly responsible for

increasing hurricane frequency and intensity, or if the sole cause has been natural cyclicality. In

any case, all scientists can agree that we need to prepare ourselves, as the hurricane threat

appears much greater than in previous periods.

28

CHAPTER 3

METHODOLOGY

The study area for this thesis includes coastal landscape within ABM habitat ranging

from Fort Morgan, Alabama approximately 20.9 km east, along a barrier island (Figure 3.1). The

trapping data acquired from the USFWS span the length of 1999-2009, but for the purpose of

this study, primarily 2003-2006 data were used for pre- and post-hurricane analysis. The data

were taken by both USFWS employees and locally hired trapping specialists within Habitat

Conservation Plans (HCPs). The trapping methods are standard protocol in accordance with the

USFWS document “Trapping to Ascertain Presence of Beach Mice.” Sherman-live traps are

supplied with cotton balls for warmth and baited with oats. The general protocol is the same, but

the number of traps and varies by the trapping location. There are 1-8 lines with 50-80 trapping

stations (1-3 traps per station) for a total of 100-500 traps set up per trapping quarter. The

trapping usually takes place over 5 nights. The study area contains ten smaller areas based on

trapping data, including: Bay to Breakers, Beach Club, Kiva Dunes, Laguna Key, Martinque,

Plantation Palms, The Dunes, Mobile Street West (MSW; western Perdue unit), Gazebo (eastern

Perdue unit), and Fort Morgan. Each of these smaller units contains similar land features, from

primary dunes to scrub dune habitat. Gazebo and Fort Morgan are protected areas within Bon

Secour National Wildlife Refuge, but the other trapping locations are completely surrounded by

residential development.

29

Figure 3.1. Partial map of Baldwin county showing the historic range of the ABM in Gulf Shores (Source: http://alabamamaps.ua.edu/contemporarymaps/alabama/counties/baldwin.jpg)

The USFWS’s data in its original format was organized into folders by trapping location

and year, containing spreadsheets within Microsoft Excel, documents in Microsoft Word and

copies of letters from trapping specialists in Adobe. Using Microsoft Excel, I pooled the number

of beach mice trapped within each location and averaged to examine seasonal trends in

population size. During 2005, there was a lack of trapping data in several locations due to

hurricane conditions and post-hurricane impacts on the areas (Carl Couret per comm. 2010). The

lapses in data were therefore adjusted by standardizing trappings using the formula:

��total trapped per season

number of locations trapped. The total of 1,279 beach mice considered for the analysis were also

organized into groups of “Before Ivan” (Winter 2003-Summer 2004), “After Ivan” (Fall 2004-

Summer 2005), and “After Katrina” (Fall 2005-Fall 2006), totaling the number of beach mice

30

caught during each period. The original trapping data reported each time a mouse was

recaptured, but for my study, a mouse was only counted toward the population the first time it

was trapped. The USFWS considers this the number of “individual captures.” Since the majority

of the data are first time captures, the analysis of population was not based on the mark and

recapture method. The data was tested and found to be non-normal, and therefore non-parametric

tests were chosen for SPSS analysis.

Two different methods, a chi-square contingency table and a Wilcoxon ranked-sum test

were used to determine the differences in beach mouse populations across trappings locations

before and after hurricanes Ivan and Katrina. Contingency table analysis is a common method of

analyzing the association between the distribution of categorical values by crosstabulation of

rows and columns to find observed counts. Using the chi-square statistic, observed counts are

then compared to the expected counts (Woodward and Eliot 2007). Klich (2002), Stillman and

Brown (1998), and Wilcove (1998) have all used contingency tables in their biogeographical

studies for statistical analysis. Klich (2002) used contingency tables to show how the occurrence

of Aspergillus species in soil and litter varied from expected distributions in biomes and

latitudinal ranges. Wilcove (1998) quantified threats to imperiled species the using chi-square

method to determine the significance of threats to species and difference in vulnerability of

species to particular threats. Stillman and Brown (1998) utilized contingency tables in order to

analyze patterns in the distribution of Britain’s upland breeding birds.

For my study, a chi-square test was performed to test the null hypothesis (H0) that there is

no association between trapping location and hurricane event by analyzing observed versus

expected frequencies. For the purpose of contingency table analysis, the number of beach mice

trapped was calculated for each individual location and split into two categories: 1.) Event one

31

(before hurricanes), and 2.) Event two (after hurricanes). Organizing the data by combining Ivan

and Katrina into one hurricane event eliminated cells with zero value for trappings post-

hurricanes. SPSS was then used to find observed counts of the row × column (r × c) at each

location, where r is trapping location and c is event. The crosstabulation was then used to detect

differences in distribution of beach mice in individual trapping areas before and after Hurricanes

Ivan and Katrina. The significance of the association in the contingency table was determined

using the chi-squared statistic.

For qualitative purposes, each trapping area was located by GPS and photographed. The

pictures were used to find what characteristics at a trapping location could lead to variances in

numbers of beach mice trapped. In October 2011, my observations in the field and photographic

evidence helped to show that differences in the terrain, vegetation, and degree of human presence

can explain the differences in observed and expected results from the chi-square contingency

table.

The second statistical analysis was performed by running Wilcoxon ranked-sum tests.

These tests can be used to compare paired data as the non-parametric alternatives to the paired t-

tests (Woodward and Eliot 2007). The test is based on the order in which the observations from

the two samples fall. The null hypothesis is generally H0; A=B meaning that the distribution of

X-measurements in populations equals those in populations B. The Wilcoxon test finds

departures from H0 by detecting location shifts. Barlow and Cameron (2003), Buse et al. (2008),

and Meffe (1984) are just a few of many that have used Wilcoxon tests for statistical analysis in

biogeographical studies. Barlow and Cameron (2003) used the Wilcoxon test to determine the if

the number of marine mammals caught in gill net fishery was reduced by acoustic devices

designed to deter marine mammals from entanglement in fishing nets. Buse et al. (2008) use

32

Wilcoxon tests to investigate variables that lead to differences between trees colonized and

uncolonized by red-listed longhorn beetles. A Wilcoxon test was also utilized by Meffe (1984) to

analyze number of fish displaced by different abiotic disturbances.

The Wilcoxon signed-rank test was used in my thesis to verify that the distributions of

the number of ABM trapped before the hurricanes are not equal to the number trapped after

hurricanes. The data for the Wilcoxon test was organized similarly to the contingency table,

combining seasonal trappings into “before hurricanes” and “after hurricanes” based on trapping

location. The test results show whether hurricanes influenced ABM population numbers through

comparison of the number differences that are positive and negative between the numbers of

mice trapped “before Ivan and Katrina” to “after Ivan and Katrina.”

33

CHAPTER 4

RESULTS

General Trapping Analysis

A total of 1297 individual mice were caught across all trapping locations from 2003-2006

(Table 4.1). The range in individuals trapped per season varied from 2 in both fall and winter

2004 to 453 in spring 2004. Before Hurricane Ivan, 968 individual beach mice were captured,

190 were captured after Ivan and 121 after Katrina. The highest number of beach mice (148)

trapped was at the Beach Club in spring 2004. Following the hurricane events of 2004 and 2005,

no beach mice were found at multiple locations.

34

2003 2004 2005 2006

Wi Sp Su Fa Wi Sp Su Fa Wi Sp Su Fa Wi Sp Su Fa

Bay to Breakers 14 6 25 0 1 0 0

Beach Club 28 19 148 35 6 8 6

Kiva Dunes 32 2

Laguna Key 14 15 14 27 5 14 0 0 0 0 0

Martinique 5 5 59 29 6 38 8 2 17 8 11

Plantation Palms 7 4 27 4 1 0

The Dunes 4 53 34 1 0 9 0 4

MSW 83 14 35 1 54 12

Gazebo 84 24 3 38 4

Fort Morgan 41 79 14 38

Total 14 181 44 128 14 453 134 37 14 131 8 2 2 34 14 69

Standardized 14 60.3 11 16 14 56.6 26.8 4.1 14 21.8 2.7 2 2 8.5 2.8 9.9

Table 4.1. Number of individual beach mice caught at each location during seasons from 2003-2006 (Wi-Winter, Sp-Spring, Su-Summer, and Fa-Fall)

After winter 2005, the beach mouse population at Laguna Key was extirpated, with 0

mice captured in the following seven seasons (Table 4.1). The population remained at 0

throughout 2007, but recolonization of the mice eventually took place (USFWS 2009). The

beach mice reappeared in winter 2008, with six individual mice trapped (Table 4.2).The

population eventually recovered its original numbers, with 36 mice caught in spring 2009. This

number (36) was greater than the highest number (27) of beach mice caught at Laguna Key in

the years 2003-2006.

35

2007 2008 2009 WI SP SU FA WI SP SU FA WI SP SU FA 0 6 20 11 9 36 18 Table 4.2. Number of individual beach mice trapped at Laguna Key after extirpation of beach mice following hurricane Katrina

Figure 4.1. Number of ABM trapped per season standardized by number of locations that trapped

The trappings of each season standardized by number of locations showed that the

highest number of beach mice trapped occurred in spring 2003 with 60.3 and 56.6 in 2004, but

only 21.8 in the 2005 and 8.5 in the 2006 seasons following the hurricanes (Figure 4.1). Note the

higher number of beach mice trapped before Hurricane Ivan in spring of 2004 compared to the

lower numbers after Ivan and Katrina.

Winter is usually the season with the highest population density, but during this study the

most ABM were trapped in the spring. Therefore it is easiest to examine the recovery of ABM

population after the hurricane by looking at the numbers of ABM trapped during the spring

(Figure 4.2). Before hurricane Ivan in 2004, the standardized number of ABM trapped was 56.5,

which decreased to 9.8 the spring after Ivan. In the spring following Katrina, the number was

0

20

40

60

80

Win

03

Sp

r03

Su

m0

3

Fa

ll0

3

Win

04

Sp

r04

Su

m0

4

Fa

ll0

4

Win

05

Sp

r05

Su

m0

5

Fa

ll0

5

Win

06

Sp

r06

Su

m0

6

Fa

ll0

6

Standardized Seasonal Trappings

Total Trapped in

Season/Number of

Trapping Locations

36

reduced further to 8.5 in 2006, but increased to 12.7 in 2007 and up to 30 in 2008. This shows

that while the population declined after Hurricane Ivan, and was further reduced by Katrina, it

only took three years for the population to return to more than half of the pre-hurricane number.

Figure 4.2. Standardized number of ABM trapped in spring seasons

Statistical Analysis

Originally, the results of the Wilcoxon test on trappings before and after Ivan showed that

Hurricane Ivan had a significant effect on the population of ABM, with 10 out of 10 trapping

14

56.5

9.8 8.5

12.7

30

40

23.5

0

10

20

30

40

50

60

Spring

03

Spring

04

Spring

05

Spring

06

Spring

07

Spring

08

Spring

09

Spring

2010

ABM Trapped in Spring

Standardized # of ABM Trapped

37

locations having greater individual trappings before Ivan than after Ivan (p = .008). A Wilcoxon

test was also run to analyze the trappings before and after Katrina, but results were insignificant

(p = 0.314) because the numbers of beach mice caught were so low after hurricane Ivan.

Therefore, the categories of “After Ivan” and “After Katrina” were combined in order to create

an “After Hurricanes” category. The Wilcoxon test showed that the combined hurricanes had a

significant effect on the population of ABM, with 10 of 10 trapping locations (Table 4.4) having

greater individual trappings before hurricanes than after hurricanes (Z = -2.803, P = 0.005)

(Table 4.3). Indeed, median number of beach mice trapped varied from 96.80 pre-hurricanes to

31.10 post-hurricanes (Table 4.2). This is also evident in Figure 4.3., showing that the number of

ABM trapped after storms was always lower than the number trapped before storms.

Figure 4.3. The number of ABM trapped before versus after storms at all locations

45

230

32

7098

42

91

132108 120

120

219

90

114

6745 52

0

50

100

150

200

250

Nu

mb

er

of

Fir

st T

rap

pin

gs

Number of ABM Trapped Before and After

Storms

Before

Hurricanes

After

Hurricanes

38

N Mean Std.

Deviation Minimu

m Maximu

m

Percentiles

25th 50th

(Median) 75th

Before Hurricanes

10 96.80 58.007 32 230 44.25 94.50 123.00

After Hurricanes

10 31.10 30.928 1 90 1.75 19.50 55.75

Table 4.3. Descriptive statistics for Wilcoxon signed rank test

N Mean Rank Sum of Ranks

After Hurricanes - Before Hurricanes

Negative Ranks 10a 5.50 55.00

Positive Ranks 0b .00 .00

Ties 0c

Total 10

a. After Hurricanes < Before Hurricanes

b. After Hurricanes > Before Hurricanes

c. After Hurricanes = Before Hurricanes

Table 4.4. Ranks from Wilcoxon signed rank test

Contingency analysis showed the difference between observed trappings and expected

trappings and an association between trapping location and hurricane event was found, (χ2 9, N =

1279 = 144.9, p < 0.001.) (Table 4.5) Examination of the cell frequencies showed that all of the

locations had more than 50% of their population before the hurricanes. In seven out of ten of the

locations >70% of total population was trapped before the hurricane events. Also, out of the total

trapped, 75.7% took place before hurricanes, meaning that there is an association with the

number of ABM trapped at different locations and “event one”, or before hurricanes. Notice that

there is a large difference (>40) between observed and expected frequency (Table 4.6) for ABM

39

trapped at Beach Club, Martinique and Laguna Key. This shows that these trapping locations

contribute most to the magnitude of the χ2 statistic.

Value df

Asymp. Sig. (2-sided)

Pearson Chi-Square 144.878a 9 .000 Likelihood Ratio 159.699 9 .000 N of Valid Cases 1279

a. 0 cells (.0%) have expected count less than 5. The minimum expected count is 8.27.

Table 4.5. Chi-square test results for ABM trapping data

Table 4.6. Chi-square contingency table

40

CHAPTER 5

DISCUSSION

Population Analysis

ABM populations naturally fluctuate on a seasonal and yearly basis (Neal and Crowder

2009); this is evident in the trapping data from the USFWS from 2003-2010 (Table 4.1).

Although the USFWS refrains from using trapping results to characterize the overall range-wide

population for ABM, this data is useful in examining population patterns caused by the effects of

hurricanes. Analysis of populations have been performed in the past regarding the numbers of

beach mice after hurricanes using trapping data (Swilling et al. 1998, Pries et al. 2009). In

general, it is important to study the effects of catastrophic events on populations, as they not only

control the estimates of population viability, but may also be more important that other factors in

determining future persistence of populations (Mangel and Tier 1994). Because the scientific

literature is split on the link between global climate change and hurricane impacts, I can only

hypothesize what will happen to the beach mouse if hurricane patterns change. Therefore the

predictions of how hurricanes may impact the beach mouse are based solely on the historical

data of how ABM populations reacted to hurricanes in the past. Regardless of whether or not

hurricane frequency and intensity are increasing, hurricanes are catastrophic events shaping the

remaining populations of ABM.

41

The results presented in the chi-square test show that 10 out of 10 locations (100%) had a

lower number of beach mice trapped following the hurricanes. More precisely, 100% of the

locations trapped 70% or more of the total number of ABM before the hurricanes. From this it

can be inferred that the ABM population is highly vulnerable to hurricane events. Further

evidence that hurricanes largely decimated beach mouse population can also be seen by

examining the standardized numbers of beach mouse trapped per season. Preceding hurricane

Ivan, the standardized numbers of beach mice trapped were 60.3 in spring 2003 and 56.5 in

2004, which significantly dropped to 21.8 in the spring after the Ivan and then again to 9.9 in the

spring after Katrina.

The trapping locations with percentages most similar in number of beach mice captured

before hurricanes and after hurricanes are Martinique, MSW, and Fort Morgan. At these three

locations, 47.9%, 33.7 % and 30.2%, respectively, of the population were trapped after the

hurricanes. The results indicate that these locations offer the best refuge for beach mice during

hurricanes. These locations should be observed for unique characteristics that make them less

susceptible to the damaging effects of hurricanes on the ABM population. While both MSW and

Fort Morgan are within protected areas, the Martinique trapping location is also the site of a

large condominium. Examining these locations using aerial photography maps (GoogleEarth

images) of ABM habitat, it is evident that these locations all have one thing in common. Out of

the ten trapping locations, these three have the most area extending into scrub habitat. The

number of beach mice caught post-hurricanes in these areas is most likely due to the larger area

of refuge and the ease of access to these higher elevations that helped the beach mice persevere

during the storm. Of all the unprotected trapping locations, Martinique is the only area that

contains a direct connection between the less vegetated frontal dunes and the higher density

42

vegetation in secondary dunes. The location also includes a long human access boardwalk from

the condominium with multiple signs to help prevent people from walking across the dunes

(Figure 5.1).

Figure 5.1 View of ABM habitat within Martinique trapping area

Laguna Key is an ideal location to examine the devastating effects of hurricanes on ABM

numbers, because the entire population was extirpated from its habitat at Laguna Key following

Hurricane Katrina. Zero beach mice were trapped after winter 2005 through the next two years.

No trapping took place in fall 2007 because beach renourishment was ongoing. According to a

trapping specialist, “the frontal dunes looked good, new sea oats were planted and the sand

fencing was well done” (per. comm. Barbara Allen 2007). Trapping resumed in winter 2007, but

no beach mice were caught because the newly planted vegetation provided no seed source for the

ABM. The beach mouse did not reappear until winter of 2008, when nine individual beach mice

43

were captured. It appears that the beach mouse only recolonized here once the vegetation was

mature enough to provide a food source.

In the past, studies have demonstrated that beach mice can recover from hurricane effects

(Neal and Crowder 2009). In my study, the back-to-back Hurricanes Ivan and Katrina severely

degraded the population of ABM and provided insufficient time for recovery between these two

storms. Examining the numbers of beach mice caught in the years following both hurricanes

showed that the population recovered from this catastrophic event, but not to their original

numbers. Three years after the hurricanes, the population recorded in the spring of 2008 (56.5)

was only 53% of the population before the hurricanes in spring of 2004 (30) (Figure 4.2). On the

other hand, populations of beach mice often make remarkable recoveries. Although the ABM has

shown the ability to recover from storms in the past, in the event of increasing hurricane

frequency and intensity their population may not be able to regain population numbers in the

same manner as before. Because most of the trapping data stops at 2008, realistic predictions

cannot be made without seeing if the population ever completely returns to its pre-storm state.

Also to be considered is the chance of increasing hurricane frequency and intensity due to global

climate change. For future studies, I suggest that the trapping data be examined post-hurricanes

to see if the population returns to the highest numbers of ABM captured pre-hurricane events,

factoring in time since previous hurricanes.

44

Factors that Hinder Beach Mouse Survival

Not only do beach mice require a variety of habitats to survive, it is even more

important that these areas are large and continuous, permitting beach mice to move between

the different habitats of higher elevation. This contiguous habitat also maintains the genetic

variability of the ABM population. Once habitats are discontinuous, the species within

becomes more susceptible to factors that further limit their population numbers. Local

extinctions are common within small, fragmented populations. Whereas it is in the best interest

of the Alabama beach mouse to protect large continuous tracts of beach mouse habitat, where

it is not possible, the best defense against range-wide extinctions is establishing multiple and

widely distributed local populations (Shaffer and Stein 2000, Oli et al. 2001, 71 FR 5515 and

71 FR 44976). This approach increases the chances that at least one population will survive

under episodic storms or other natural disturbances (71 FR 5521).

Figure 5.2. GoogleEarth image of trapping locations in Gulf Shores, AL

45

Figure 5.3. GIS-created map of ABM critical habitat and superimposed trapping locations (Source: GIS coordinator Drew Rollman of the USFWS)

The entire ABM population is concentrated in a 20.9 km stretch of habitat adjacent to

the coastline (USFWS 2009), making them vulnerable to stochastic events which have the

potential to completely wipe out their population. Figure 5.2 and 5.3. show the disconnectivity

of populations of beach mice within their habitat range. Although the USFWS considers all of

the area on the map (Figure 5.2) critical beach mouse habitat, the areas within the habitat are

fragmented up by human development. Unfortunately, in the majority of estimated ABM

habitat, habitat loss increases as development continues to take expand into remaining beach

mouse territory (USFWS 2003, 2005b and 2008). In the past several years, while the beach

mouse has been recovering from the 2004 and 2005 hurricane seasons, there has been a net

loss of habitat due to development (Neal and Crowder 2009). Also to be considered is the

economics of the Gulf Coast. Further recovery of ABM habitat is at a loss to economic activity

with human development along the Gulf Coast. Perhaps a higher value of the ABM to

biodiversity and its role in the coastal ecosystem should be considered to maintain current

management practices of the ABM and hinder further development within ABM habitat.

46

Ongoing habitat loss continues to influence landscape structure, with habitat loss

generally leading to increased fragmentation of habitats (or the breaking apart of habitat,

independent of loss (Fahrig 2003, Weins 1995). Endangered species can often be rescued from

red-listing by a relatively modest increase in habitat area and associated average populations size

(Wilson 1992, Patton et al. 2005). Restoration of “relatively contiguous tracts of suitable ABM

habitat over a wider area with multiple independent local populations” would increase the

probability of future ABM persistence (Shaffer and Stein 2000, Oli et al. 2001, 71 FR 5515, 71

FR 44976, USFWS 2009, 15). Unfortunately, the ABM is restrained by human presence on all

sides, so the only possibility of habitat increase would be to relocate or reintroduce a part of the

ABM population.

Reintroduction efforts to return species to parts of their historical ranges where they were

extirpated, often involving release of either captive-bred or wild-caught individuals, has a poor

overall success rate worldwide (Armstrong and Sedon 2007). Van Zant and Wooten (2003)

translocated Choctawhatchee beach mice (Peromyscus polionotus allophyrys), resulting in nearly

100% loss of translocated mice. They suggest that this was an unanticipated outcome and future

efforts should be approached with caution. On the other hand, many reintroduction programs

have been pivotal to recovery from near-extinction (Islam et al. 2011, Asa 2010, Jachowski et al.

201l, Raesly 2001). The Arabian Oryx (Oryx leucoryx), the black-footed ferret (Mustela

nigripes), the river otter (Lontra canadensis), the Red wolf (Canis rufus) and Mexican grey wolf

(Canis lupus baileyi) were all believed extinct in the wild, yet small numbers of individuals still

existing in captivity served as founders in recovery of those species. These studies show the

importance of reintroductions in endangered-species recovery. There has been discussion of

reintroduction of ABM to the Gulf State Park (GSP) in Gulf Shores. Historically, this location

47

was the eastern-most extent of the ABM population, but the population of ABM here has been

isolated and extant for a long time (USFWS 2009). GSP is the USFWS’s ideal location for

reintroduction of the ABM according to the International Union for the Conservation of Nature’s

(IUCN). The IUCN guidelines define reintroduction as an attempt to establish a species in an

area that was once part of the historical range but from which it has been extirpated or became

extinct (IUCN 1998). GSP may not be the ideal for successful ABM reintroduction considering

the population at GSP has been extirpated three times in the past (Volkert 2005). Area at a higher

elevation with scrub habitat for hurricane refuge would be best, as even the storm surge from a

Category 1 hurricane would inundate the area (Figure 5.4).

Figure 5.4. Map of eastern Gulf Shores showing Gulf State Park (Source: http://www.iwr.usace.army.mil/nhp/docs/Baldwin%20Surge%20Plate%209%20-

%203Dec09.pdf)

The importance of dunes to the ABM has been defined in multiple studies, as the mice

rely on the dune ecosystem for food, burrow sites, and refuge from weather and predation. If

another major hurricane were to hit the area in the near future, the beach mice might not have

48

the same areas to escape to high ground and seek protection. While most of the flora and fauna

of the Gulf Coast have evolved to withstand the effects of periodic hurricanes, I hypothesize

that the ABM has not adapted to survive hurricane effects amplified by anthropogenic factors in

the future.

In the event that tropical cyclone frequency or intensity increase in upcoming years due

to global climate change, the chances that the ABM will have enough habitat to survive or seek

shelter during hurricanes are lowered substantially. If one hurricane destroys the frontal dunes,

the secondary dune and scrub habitat will then be more exposed in the event of the next

hurricane. The short time period between Ivan and Katrina allowed less time for the vegetation

to re-establish itself in the sand dunes within ABM habitat. Habitat loss and fragmentation has

left only 991.5 hectares of habitat for the ABM, the majority of which is subject to future

meteorological effects of hurricane such as storm surge, salt spray and high velocity winds (Bill

Pearson per. comm.). According to Baldwin County storm surge maps (Figure 5.5) based on

2008 SLOSH models, even under a Category 1 storm the beach mouse would have to be at an

elevation higher than 1.3 meters to seek refuge from storm surge at high tide with no wave

action.

49

Figure 5.5. Gulf Shores storm surge map (Source: http://www.iwr.usace.army.mil/nhp/docs/Baldwin%20Surge%20Plate%207%20-

%203Dec09.pdf)

Factors that Aid in Beach Mouse Survival

Currently, the USFWS are doing everything they can to keep the remaining populations

of ABM intact by keeping people from walking in their habitat, having completely protected

areas (Bon Secour), and monitoring the population through trapping. At the Bon Secour National

Wildlife Refuge, eight km of beach create a protected habitat for the remaining population of

Alabama beach mouse and other endangered species. The name Bon Secour comes from the

French words meaning “safe harbor,” and it is because of the protection of this intact coastal

beach system that the ABM survives at all (Frosch 2003). Bon Secour habitat is unique because

it has higher habitat heterogeneity than other beach mouse areas (Swilling et al. 1998). The

50

majority of the ABM research efforts take place here, because the species thrives in dunes and

vegetation that are reminiscent of those that once existed all over the Gulf Coast

(fws.gov/bonsecour).

Figure 5.6. Map of Bon Secour National Wildlife Refuge (Source: http://www.fws.gov/bonsecour/images/refugemap.jpg)

Although the ABM is quite vulnerable to further reduction in population size, there is

evidence that the species is able to tolerate some level of hurricane impact. Beach mice have

shown the ability in the past to adapt to hurricanes, and have even been able to recover from

catastrophic events that completely wiped out their population to zero. ABM populations are

naturally dynamic and have the ability to withstand bottlenecks (Wooten 1994), or a severe, but

temporary population restriction (Maruyama and Fuerst 1984). Beach mice first adapted to

hurricanes by constructing high quality burrows clumped in dispersal so they can survive the

harsh beach environment (Rave and Holler 1992, Swilling and Wooten 2002). It has been shown

that beach mice utilize the scrub dunes during tropical cyclones and other storm events to

alleviate which reduces the harmful effects on beach mice population (Oli et al. 2000). After

51

hurricanes, USFWS witnessed the slow return of the beach mice to previously occupied areas. In

Laguna Key and West Beach where beach mice were completely extirpated from hurricanes,

recolonization occurred naturally a few years later in 2008 (Barbara Allen per comm. 2008). On

the other hand, the population of beach mice at GSP, which has been wiped out three times, was

not so lucky. The numbers here still remain at zero, probably because of its isolated location. In

addition, the ABM increases reproduction post-hurricane, although this can likely be attributed to

normal recovery from already low density populations (Traylor-Holzer et al. 2005).

Habitat restoration projects help to improve ABM habitat quality of areas recovering after

hurricane. These efforts include sand fencing installed to aid in rebuilding dunes, planting sea

oats and other native vegetation to restore dunes, and application of fertilizer to help the plants

grow (www.fws.gov/daphne/es.abm.html). In addition, the USFWS offers suggestions to local

residents to help aid in ABM population recovery including regulating beach access points,

limiting pedestrian and vehicular use, controlling cat activity, properly disposing of trash to

inhibit competitive from other rodent populations, and avoiding the use of deadly devices (i.e.

posions, mouse traps, etc.) for killing rodents in ABM habitat

(www.fws.gov/daphne/es.abm.html).

52

CHAPTER 6

CONCLUSIONS

The factors that aid in ABM survival are largely outweighed by the factors that hinder the

future persistence of their population. Because the ABM faces greater than normal disturbances

both from humans (i.e. habitat loss and fragmentation) and the natural environment (i.e.

hurricanes and climate change), I postulate that the ABM population will be completely extinct

within the near future. The ABM has survived through the past thirty years as a small population,

but any future decrease in habitat size could push the population to extinction. Although the

ABM has adapted to storm surge by moving to higher ground of the scrub/transition areas during

hurricanes, future storms could alter the habitats so severely that the beach mouse would no

longer have a safe habitat available during storms. In other words, back-to-back storms could

potentially wipe out the frontal dunes which protect the beach from erosion and further storm

damage. Once the protective barrier of the frontal dunes is destroyed, there is the potential for

more damage to take place in the areas that were previously considered refuges for beach mice

during hurricanes. Even with the possibility of reintroduction or translocation of the ABM, there

is no place for successful recolonizations, because of the human presence on all sides of

available beach mouse habitat and vulnerability of habitat to storm surge. Unless there is no

further loss ABM habitat, especially higher elevation scrub habitat, the future of their population

looks grim.

53

One source of uncertainty in this study is the lapse in trapping data during different

seasons and across sites. Also to be considered is that these estimates are based raw trapping

data; they are in no way valid indices of actual population size. For future studies, I suggest that

estimates of population size be found using a program such as Vortex or Capture, as data is not

sufficient enough to produce population estimates. Regardless, there are likely uncertainties with

all scientific studies and management strategies for the ABM and other endangered species can

still be formed from the analysis in this study.

54

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