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EcoQuest Education Foundation Directed Research Project 2019

COMPARING POPULATION DENSITY OF PARYPHANTA

BUSBYI AND SMALL MAMMALIAN PESTS

Brooke E. Gauthier

EQ988(191)

Taking the weight (grams) of a P. busbyi snail in the Millennium Forest, Waipoua Forest,

Northland, New Zealand.

Undergraduate report, (NR: 663, Directed Research Project) written in partial fulfilment of semester requirements at EcoQuest Education Foundation, New Zealand. This is a graded report and EcoQuest takes no responsibility for errors in sampling or analysis that it may contain. No part of this report may be reproduced, circulated or stored in any form without the prior written permission of EcoQuest Education Foundation, 1204 East Coast Road, R D 3, Pokeno, New Zealand.

COMPARING POPULATION DENSITY OF PARYPHANTA BUSBYI AND SMALL

MAMMALIAN PESTS

At two Sites in the Waipoua Forest, Northland, New Zealand

Brooke E. Gauthier

EcoQuest Education Foundation1204 East Coast Rd R.D.3, Pokeno 2473New Zealand

May 2019

Contents

1 Introduction.........................................................................................................................9

1.1 Overexploitation of forests:.........................................................................................9

1.2 Pest establishment:......................................................................................................9

1.3 Importance of restoration ecology:...........................................................................10

1.4 Pest management:......................................................................................................10

1.5 Species of interest:....................................................................................................11

1.6 Objective:..................................................................................................................11

2 Methods.............................................................................................................................13

2.1 Permissions:..............................................................................................................13

2.2 Nocturnal activity assessment:..................................................................................13

2.3 Day quadrat surveys:.................................................................................................15

2.4 Tracking Tunnels:.....................................................................................................15

2.5 Biosecurity................................................................................................................17

2.6 Data Analysis............................................................................................................17

3 Results...............................................................................................................................18

3.1 Diurnal Quadrats.......................................................................................................18

3.2 Nocturnal Surveys.....................................................................................................19

3.3 Snail Shell Measurements.........................................................................................22

3.4 Tracking Tunnel Surveys..........................................................................................23

3.5 Comparison of 2018 and 2019 Data..........................................................................25

4 Discussion.........................................................................................................................32

4.1 Diurnal Quadrats and Nocturnal Surveys..................................................................32

4.2 Snail Shell Measurements.........................................................................................34

4.3 Tracking Tunnels.......................................................................................................34

4.4 Comparisons Between 2018 and 2019......................................................................35

4.5 Further Improvements...............................................................................................36

Acknowledgements...................................................................................................................38

References.................................................................................................................................39

Appendix 1................................................................................................................................41

Abstract

Throughout the Waipoua Forest, Northland, New Zealand, the kauri snail Paryphanta busbyi

has been monitored, along with mammalian pest activity. Both Kauri snails and mammalian

pests have been compared between two forest sites to determine whether this threatened snail

species is at risk. Comparing an older growth forest site and a plot planted 19 years ago, en-

ables assessment of whether the recently planted forest has become suitable habitat for kauri

snails. It is expected that P. busbyi will be more abundant in the older growth forest compared

with the recently planted plot due to the denser leaf litter. We utilize diurnal quadrats, noctur-

nal transects and tracking tunnel transects to compare relative abundance between sites.

Nocturnal transects reveal that the older growth forest contains a high abundance of Kauri

snails, with a mean of 0.8 snails observed per meter searched. Significantly fewer snails were

observed in the recent forest block, with only 0.016 snails observed per meter searched. Al-

though, very few snails were observed in the recent forest block, their presence indicates this

forest is becoming suitable habitat for kauri snails. Daily quadrats yielded few snails in both

forests. Tracking rates of small mammalian pests were higher in the recently planted forest.

Overall, it is expected that the P. busbyi population will increase in the Millennium Forest

with continued growth and succession of the forest.

Key words: predation; Kauri snail; reproduction; pest management; older growth

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1 Introduction

Worldwide, human communities and urban developments have greatly degraded the Earth’s natural

ecosystems, taking habitats and nutrients away from vast varieties of flora and fauna. In order to fix

these problems, humans attempt “restoration ecology” which promotes people to actively intervene

and manage degraded or damaged ecosystems (Norton 2000). This also includes restoring, or partially

restoring, biotic communities (Norton, 2000). Restoration ecology includes stopping degradation

before it happens, implementing methods to return the land to its former habitat and incorporating

restoration goals into current land-management strategies (Hobbs and Norton, 1996). Using these

themes, countries and communities have been taking steps to decrease impacts during resource

extraction and the trading of goods.

1.1 Overexploitation of forests:

Due to the wide range of products that can be created from timber, temperate forests have been one of

the most heavily exploited biomes, loosing 29.7 million hectares in 2016 (Weisse and Goldman,

2017). The global tree cover loss in 2016 is 51% higher than the loss in 2015, which totals an area

about the size of New Zealand (Weisse and Goldman, 2017). These losses have led to an array of

detrimental impacts to the environment, one major impact being habitat destruction. With the loss of

land to urbanization, native flora and fauna around the world are quickly losing their natural

environment, causing extinction and niche shifts. Species competition has increased greatly, leading

to loss of biodiversity and genetic variation.

1.2 Pest establishment:

Prior to human establishment, around 1,000 A.D., 55% of the land cover in New Zealand was native

forest; since then native forests have been decreased to 20% of the land cover (Ministry for the

Environment, 1997). Forests throughout the mainland have been reduced to a few remnants, which

have been further degraded by livestock when animal products increased in demand (Stringer et al.,

2003). Settlers also introduced mammalian pests, more specifically brushtail possum (Trichosurus

vulpecula), feral pigs (Sus scrofa), ferrets (Mustela furo), hedgehogs (Erinaceus europaeus), mice

(Mus musculus), rats (Rattus spp.), small cats (Felis catus), stoats (Mustela spp.) and weasels (M.

nivalis). On the mainland and close islands, these pests have caused many damages to the little native

forest and fauna leftover from urbanization. Brushtailed possums are notorious for causing canopy

defoliation due to their opportunist feeding patterns of foliage, flowers, fruit and forest birds (Payton

et al., 1996). Ship rats and stoats have become predators to endemic and native mainland bids, one of

which is New Zealand’s beloved Kiwi (Apteryx spp.) (Brown et al., 2015).

EcoQuest Education Foundation EQDRP 5/19 BGauthier

10

1.3 Importance of restoration ecology:

Considering New Zealand’s economy is based heavily on biological resources and services provided

from healthy ecosystems, New Zealanders have strongly adapted restoration ecology into their culture

to reduce mammalian pests and convert degraded habitats to their original state (Department of

Conservation). About 70% of New Zealand’s tourists come to the country for nature-based activities.

Being that tourism is a substantial part of New Zealand’s income, restoring degraded habitats would

be economically beneficial and worthwhile (Simmons, 2013). 5% ($10.6 billion) of New Zealand’s

gross domestic product is from agriculture, leading to an importance in controlling pests and

minimizing their impacts, not only on the natural environment but also altered land (Environment

Guide).

1.4 Pest management:

80-million years ago, New Zealand separated from Pangea, isolating the country from mammal

occupancy (Gibbs, 2008). Due to the isolated nature of New Zealand’s continent, native fauna adapted

without mammalian pests. From Polynesian settling in the 13 th century and European settling in 17th

century, mammalian pests were introduced to the islands, causing extinction and predation on native

species (Gibbs, 2008). For the sake of saving biodiversity and native fauna population sizes, pest

management has become very important. In order to decide on a pest management strategy, species

presence and relative abundance must be taken into account. This can be determined through tracking

tunnels which bait pests to a tunnel with an ink pad in the middle. The pests step on the ink pad and

leave a print behind as they leave the tunnel, giving surveyors an idea of pest distribution and whether

or not pest control action must be taken (Gillies and Williams, 2013). This is very important because

once presence and relative abundance of pests is determined, a management plan can be put into place

to protect specific flora or fauna species.

There are several different types of pest management used on mainland New Zealand, aerial and

ground techniques have both been used to control, not eradicate, pests. A common aerial technique is

dropping 1080, sodium monofluoroacetate, from helicopters that drops 1 to 3 kilograms of pellets

every hectare (Clarke, lecturer, 2019; Griffiths and Barron, 2016). The Department of Conservation

allows for a permissible level 0.08% of 1080 in each pellet, much less than the amount needed to kill

a human (Clarke, lecturer, 2019). This chemical kill herbivore and carnivorous mammalian pests with

little environmental impacts due to the quick degradability of the chemical in water and low chance of

bi-kill. Ground techniques include trapping such as run-throughs and sentinels. These traps are

normally baited with peanut butter and target rats, possums and stoats. Run-throughs and sentinels are

similar in that they are a one kill trap that snaps the pests neck and must be manually reset (van

Gessel, lecturer, 2019). Run-throughs are placed on the ground and baited mainly for rats and mice.


11

Sentinels are often nailed the bole of trees, off the ground to prevent any native birds, such as Kiwi’s,

from sticking their head into the trap. This trap mainly targets possums and stoats (Landcare

Research). Tracking tunnels can also be used after a management plan has been enacted to monitor

the effectiveness of the pest control strategy. By controlling these pests, less damage will be inflicted

on native New Zealand forests and the fauna that live within in it.

1.5 Species of interest:

The Rhytididae family consists of medium-sized predatory air-breathing land snails. New Zealand has

10 genera, 32 species and 9 subspecies (Spencer et al., 2004). One of these species is the Kauri snail,

Paryphanta busbyi. This species is found from Northland to the Hen Islands and in the Waipu Hills

(Spencer, Brook and Kennedy, 2006). They prefer to inhabit moist areas of forest and native scrub or

areas of native scrub that are dominated by introduced wild ginger (Hedychum spp.) (Parrish, Sherley

and Aviss, 1995). P. busbyi feed on earthworms, insect larvae, insects found in leaf litter, Rhytida

snails and other kauri snails (Parrish et al., 1995). The highest density of snails can be found in soil

with high fertility where earthworm abundances are greater. During the day, the snails hid under the

leaf litter, woody debris, rocks and are sometimes found slightly buried in the soil, possibly to reduce

water loss (Stringer et al., 2003). At night, P. busbyi snails can be found traveling on top of the leaf

litter and are highly mobile, moving approximately 10 meters of two weeks (Stringer et al., 2003;

Stinger, et al., 2002). Maturity is reached around 3 years of age, but it is predicted that individuals can

continue to live up to 25 years (Parrish et al., 1995). Their shells, at maturity, are a flattened spiral

about 6.3 to 7.6 centimeters across and a dark greenish color (Encyclopedia of New Zealand, 1966).

Prior to human settlement, the Kauri snail was found in all parts of Northland. Today, species

abundance has been subject to small sections of land due to human involvement and habitat

degradation (Department of Conservation, 1995). In a restoration ecology effort to increase P. busbyi

population abundance, native trees were planted on Waipoua Forest trust land in 2000. This land is

now called the Millennium Forest. Another section of land that holds Kauri snails is an older growth

land of an unknown age, called the Triangle Forest. Due to the small abundance of live snails found in

the Millennium Forest from mammalian predators, the Waipoua Forest Trust wants to further

implement pest control.

1.6 Objective:

This is a long-term monitoring project conducted by EcoQuest, a study abroad sustainability program,

to document the effect of pest control on the Waipoua Forest Trust land. This project started as

invertebrate monitoring by looking for geckos and shifted towards P. busbyi monitoring in 2018. The

trust has prioritizing feral pig, rat and stoat trapping, along with weed control. In order to determine

whether pest control is still needed, and for what species, P. busbyi abundance in the Millennium


12

Forest and Triangle Forest are to be monitored and compared. To do this, surveyors will: use transects

to estimate snail abundance present in each forest type, compare the two different methods for

assessing snail abundance and size distribution, document habitat characteristics where snails are

found and use tracking tunnels to assess relative abundances of mammalian predators in an older

growth and restored forest. It is expected that there will be a higher abundance of P. busbyi

individuals in the Triangle Forest due to the dense leaf litter layer on the ground from the older

succession of the forest and lower abundance of mammalian pests. It is also expected that there will

be an edge effect on the transects, leading to the highest abundance of P. busbyi snails in the middle

transect section during the nocturnal surveys.


13

2 Methods

Two different forest types, an early successional and an older growth, managed by the Waipoua

Forest Trust have been monitored to observe the abundance of P. busbyi snails and assess small

mammalian pest activity (). The early successional forest is part of a restoration project that began in

2000 which planted native bush on past agriculture land, creating the Millennium Forest. The older

growth forest is called the Triangle Forest and has an undetermined age.

Figure 1. Map of the Waipoua Forest trust’s land in Northland, New Zealand. The Millennium Kauri Forest, planted in 2000, is outlined in yellow, while an older growth forest (Triangle Forest) of an unknown age is outlined in orange.

2.1 Permissions:

The Waipoua Forest Trust invited EcoQuest to perform these surveys and the Native Forest Trust

provided a living space for the surveyors for the week of data collection. No handling permits were

necessary to work with the kauri snails and Te Roroa, the local iwi, fully supported the work being

conducted.

2.2 Nocturnal activity assessment:

Nocturnal activity assessments were performed each night, with the goal of completing five nights of

surveying in a row and one night of practice. Two, 600-meter-long transects were measured out and

marked with flagging tape, one in the Millennium Forest and one in the Triangle Forest. The transects

start at the edge of the forest at both locations and are were set up in the same location as last year’s,


14

2018, transects. Pink flagging tape and reflective pegs were placed along the transects to help keep

surveyors on the examination path. Every 50 meters, two pieces of pink flagging tape were wrapped

around a tree, indicating 50 meter marks (Figure 4). After practicing together for one night, two teams

were created, four people in the Triangle Forest and three in the Millennium Forest. Breaking into two

teams allowed for both sites to be surveyed at the same time each night for direct comparisons

between data. Site data has been recorded at the start of each transect prior to being walked: location,

transect number, date, time, names of investigators, habitat and weather information. Each night,

transects were walked an hour after sundown with different starting points to minimize bias due to

time of night. Surveyors scanned ferns, matted grasses, low foliage, ground litter and bare forest floor

for P. busbyi snails with a head torch. When coming across the bole of a tree, surveyors shined their

headlight beam from the ground up the bole and across logs and debris. Foliage or loose pieces of

bark were gently moved aside, if needed.

When a snail was located, it’s length, width, height, aperture width and maximum aperture

opening were recorded using a caliper (Figure 2). Other recorded information included: time found,

weight, microclimate information, age class and additional biological notes. If an empty shell, also

known as a dead snail, was found the time and probable cause of death was recorded.

Figure 2. Representation of measurements be taken of kauri snail shells. Figure A) length of whole shell, B) width of entire shell and C) height of entire shell and width of aperture from (Ballance 1985). D) Representation of the maximum opening of kauri snail shell aperture shown as a red line, sketch from (Stringer et al. 2000)

Age class, adult or juvenile, was determined by looking at the aperture structure. Snails were

considered adults if their shell’s aperture formed a hard-rounded ridge at the edge (Figure 3). If the

snail was considered a juvenile, the aperture had a soft lip where the periostracum projects past the


15

ostracum (Figure 3). Small number tags on dynamo tape were created used a labeling machine.

Surveyors lightly sanded the shell with sandpaper and attach the label, sealing it with superglue. Once

the label was adhered, the snail was placed back where it was found.

Figure 3. Diagram of a Paryphanta busbyi watti shell. Figure B) shell of a juvenile, C) shell of an adult, sketch from (Stringer and Montefiore, 2000).

2.3 Diurnal quadrat surveys:

In both the Millennium and Triangle Forest, two 20-meter-long by 5-meter-wide quadrats were set up

and walked by the surveyors, giving a total of four quadrats. These quadrats were set up in the same

location as last year’s, 2018, quadrats. Searching included six people sorting through leaf litter,

turning over stones, and logs, or any other objects snails could be hiding under during the day while

one person recorded any pig foraging and measurements of found snails. Each quadrant would be

searched by two people to increase time management and efficiency. When a snail was located, the

distance of the snail from the 20-meter length tape was measured and recorded. Width, length, height,

aperture height, maximum opening, weight and specific local information were recorded for each

observed snail. Snails shells were sanded with sandpaper and given a number. Once the surveyor was

done with the snail, they put it back exactly where they found it. Empty shells have been measured

and the probable cause of death was determined. Present vegetation, altitude and evidence of pig

foraging along the transect was also recorded.

2.4 Tracking Tunnels:

To determine the presence of pests within the study areas, transects of ten Black Trakka tracking

tunnels, placed 50 meters apart, were placed on the Waipoua Forest Trust’s land. One line was placed

in the Triangle Forest and two lines were placed in the Millennium Forest. Yellow flagging tape was

tied around nearby trees or branches to indicate the presence of a tunnel to surveyors and the tape was

labeled 1 through 10 based on transect location, 1 being at 0 meters and 10 being at 450 meters

(Figure 4).


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Figure 4. A tree in the Triangle Forest next to a tracking tunnel with two pieces of pink flagging tape to indicate a 50-meter mark along the transect and yellow flagging tape labeled #6 to indicate the presence of tracking tunnel #6 at 250 meters.

Gotcha Traps LTD Tracking Tunnel card was placed in the tracking tunnels and were changed each

morning, around 10:00. The Tracking Tunnel card had a vegetable oil ink pad placed in the center

with white paper on both sides. In order to bait the recording paper, food was placed in the center of

the ink pad, encouraging mammals, insects and invertebrates to enter the tunnel, step on the pad and

leave behind prints as the left the tunnel (Figure 5). For the first three nights, the tunnel was baited

with peanut butter, while the last, fourth night, was baited with chicken cat food. The first three nights

were baited mainly for rats and mice, while chicken cat food was used to bait stoats. Prints on the

paper were examined, giving an activity estimate per species each night. Targeted pests included:

mice (Mus musculus), rats (Rattus spp.), hedgehogs (Erinaceus europaeus), and stoats. Invertebrates,

ants and wētā (Anostostomatidae spp. and Rhaphidophoridae spp.) tracks were also examined.


17

Figure 5. Black Trakka tracking tunnel (back) with Gotcha Tracking tracking card (front). Tracking card has vegetable oil based black ink in the center with a dollop of peanut butter in the crease.

2.5 Biosecurity

Within the Waipoua Forest is the presence of Phytophthora agathidicica, or PTA, an oomycete or

fungal-like soil borne pathogen. This pathogen moves through water and saturated soil, attacking

Kauri trees, Agathus austalis, through the root systems as zoospores. To ensure that the pathogen is

not further spread, wash stations with a 2% trigene/sterigene solution have been set up at the

Millennium Forest and Native Forest Trust office, which housed EcoQuest during data collection.

Boots were washed and scrubbed after every site visit with the trigene solution and all equipment was

cleaned prior to leaving the forest site.

2.6 Data Analysis

All data was stored and analyzed in spread sheets on Microsoft Excel (V 15.28). ANOVA (single

factor) tests and post hoc t-tests with Bonferroni correction were utilized.


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3 Results

From 11/04/2019 to 17/04/2019, diurnal quadrats, nocturnal surveys and tracking tunnel surveys were

taken in the Millennium Forest and Triangle Forest, Waipoua Forest, Northland, New Zealand. From

this, it was observed that a total of 27 P. busbyi shells were found in the diurnal quadrats (Table 1)

and 276 P. busbyi shells were found during the nocturnal surveys (Table 2). The highest abundance of

snails were found in transect two in the Triangle Forest (Figure 6). Of the 250 found live snails, 231

were found on leaf litter (Figure 8). The highest mean number of snails was found in the Triangle

Forest between 21:31 and 22:00 with a mean of 5.8 live snails per 30 minutes (Figure 9). The majority

of snails were found in the 51-60 mm length class (Figure 10) and 31-40 gram weight class (Figure

11).

3.1 Diurnal Quadrats

Between 12/04/2019 to 17/04/2019, four diurnal quadrats were surveyed, two in the Millennium

Forest and two in the Triangle Forest. In total, 27 P. busbyi shells were found, 17 of those shells were

empty and 10 contained a live snail (Table 1). On 13/04/2019, Millennium A quadrat was analyzed

with a result of six snail shells found, four of those shells being empty and two contained alive snails

(Table 1). On 17/04/2019, Millennium B quadrat was analyzed, with a total finding of five P. busbyi

shells, all of which were empty and had signs of predation (Table 1). Both Triangle Old quadrats were

completed on 14/04/2019. Quadrat A had a total of 11 snails found, three empty shells and five alive

shells; quadrat B had a total of five found P. busbyi shells, all of which were empty and had signs of

predation (Table 1).

Table 1. Total amount of kauri snails found during the diurnal quadrats at the Millennium Forest and the Triangle Forest, Waipoua Forest, Northland, New Zealand from 13/04/2019 to 17/04/2019.

Quadrat Empty Shells Alive Snails Total

Millennium A 4 2 6

Millennium B 5 0 5

Triangle Old A 3 8 11

Triangle Old B 5 0 5

Total 17 10 27


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3.2 Nocturnal Surveys

Over the course of six consecutive nocturnal survey nights, 12/04//2019 to 17/04/2019, one of which

was a practice night, a total of 276 P. busbyi shells were found (Table 2). Of these 276 found shells,

26 shells were empty and 250 contained alive snails (Table 2). Between the three transect sections in

the Millennium Forest, eight empty shells were found and nine alive snails were found, giving a total

of 17 found P. busbyi shells (Table 2). Between the three transect sections in the Triangle Forest, 17

empty shells were found and 241 alive snails were found, totaling 267 found P. busbyi snails (Table

2).

Table 2. Total amount of kauri snails found during the nocturnal survey at the Millennium Forest and the Triangle Forest, Waipoua Forest, Northland, New Zealand from 11/04/2019 to 17/04/2019.

Transect Empty Shells Alive Snails Total

Millennium 1 5 0 5

Millennium 2 3 6 9

Millennium 3 1 3 4

Triangle Old 1 6 70 76



Total 27 249 276

When considering snails found in accordance to distance searched in transect section one of the

Triangle Forest, an average of 0.495 snails were found per meter (Figure 6). Section three had the

smallest average with 0.085 live snails per meter, while section two of the Triangle Forest had the

highest average with 1.86 live snails per meter (Figure 6).

Triangle 1 Triangle 2 Triangle 30

0.20.40.60.8

11.21.41.61.8

2

Figure 6. Mean number of alive snails per meter per transect section during the nocturnal survey in the Triangle Forest, Waipoua Forest, Northland, New Zealand from 11/04/2019 to 17/04/2019.


20

Of the two 600-meter nocturnal transects in the Waipoua Forest, the Triangle Forest had a higher

abundance of live snails with a mean of 0.813 snails per meter, while the Millennium Forest had a

mean of 0.016 snails per meter (Figure 7).

Triangle Millennium0

0.10.20.30.40.50.60.70.80.9

Forest Type

Mea

n Sn

ail A

bund

ance

Figure 7. Mean snail abundance per meter for the 600-meter nocturnal transects in the Triangle and Millennium Forest, Waipoua Forest, Northland, New Zealand from 11/04/2018 to 17/04/2019.

Throughout the nocturnal surveys, taken from 11/04/2019 to 17/04/2019 at the Millennium Forest and

Triangle Forest, Waipoua Forest, Northland, New Zealand, the total number of live snails on three

different substrate types (leaf litter, log and grass) were recorded. Of the 241 live snails found in the

Triangle Forest, 228 snails were found on leaf litter, 27 snails were found of logs and zero snails were

found on grass; showing that 88.7% of snails were on leaf litter (Figure 8). Nine alive snails found in

the Millennium Forest, all of which were found on grass substrate (Figure 8).

leaf litter logs grass0123456789

10

Substrate Type

Tota

l Num

ber o

f Liv

e Sn

ails

Figure 8. Live snail abundance per substrate during the nocturnal survey in the Triangle and Millennium Forest, Waipoua Forest, Northland, New Zealand from 11/04/2019 to 17/04/2019. The Triangle Forest is represented in dark grey, while the Millennium Forest is represented in light grey.


21

Comparing the Triangle and Millennium Forest, the Tringle Forest had significantly more snails

found per 30-minute time interval than the Millennium Forest (two tailed paired t-test: t 4= 3.85,

P<0.0125). The first recorded snail found at Triangle Forest was at 19:10, while the last was found at

00:08 (Figure 9). In the Millennium Forest, the first shell was found at 19:17 while the last was found

at 21:19 (Figure 9). From this, 30-minute time intervals have been created starting at 19:00 and

ending at 00:30. For the Triangle Forest, the highest mean number of live snails was found between

21:31 and 22:00 with 5.8 live snails per 30 minutes (Figure 9). For the Millennium Forest, the highest

mean number of live snails was found between 20:01 and 21:00 with 0.6 snails per 30 minutes (Figure

9). From 00:01 to 00:30, surveyors only looked-for snails until 00:08 in the Triangle Forest, giving in

inaccurate representation of the total number of P. busbyi individuals that could have been found

during the time frame.

19:00-19:30

19:31-20:00

20:01-20:30

20:31-21:00

21:01-21:30

21:31-22:00

22:01-22:30

22:31-23:00

23:01-23:30

23:31-00:00

00:01-00:30

0

1

2

3

4

5

6

7

Time Invervals (30 minutes)

Mea

n N

umbe

r of L

ive

Snai

ls

Figure 9. Average number of live snails per 30-minute time intervals during the nocturnal survey from 19:00 to 00:30 in the Millennium and Triangle Forest, Waipoua Forest, Northland, New Zealand from 11/04/2019 to 17/04/2019. The Triangle Forest is represented in the lighter gray line while the Millennium Forest is represented by the darker gray line.


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3.3 Snail Shell Measurements

The largest live snail found between the nocturnal surveys and diurnal quadrats had a shell 68.93 mm

in length and the smallest was 12.95 mm (Figure 10). The greatest number of live P. busbyi

individuals were found in the 51-60 mm length class with 81 snails, while the smallest number of live

P. busbyi individuals were found in the 10-20 mm age class with five snails (Figure 10).

10-20 21-30 31-40 41-50 51-60 61-700

102030405060708090

Length of Snails (mm)

Num

ber o

f Sna

ils

Figure 10. Number of alive snails by length class (millimeters) from the nocturnal surveys and diurnal quadrats in the Triangle Forest and Millennium Forest, Waipou Forest, Northland, New Zealand from 11/04/2019 to 17/04/2019.

The heaviest live snail found between the nocturnal surveys and diurnal quadrats was 58 grams and

the smallest was 0.6 grams (Figure 10). The greatest number of live P. busbyi individuals were found

in the weight class 31-40 grams with 70 snails while the smallest number of live P. busbyi individuals

were found in the 51-60 gram weight class with 11 snails (Figure 11).

0-10 11-20 21-30 31-40 41-50 51-600

1020304050607080

Weight of Snails (g)

Num

ber o

f Sna

ils

Figure 11. Number of alive snails by weight class (grams) from the nocturnal surveys and diurnal quadrats in the Triangle Forest and Millennium Forest, Waipou Forest, Northland, New Zealand from 11/04/2019 to 17/04/2019.


23

3.4 Tracking Tunnel Surveys

From November 2017 to April 2019, no nice were found in the Triangle Forest (Figure 12). In the

Millennium Forest, all years, expect for November 2018, had mice activity in the tracking tunnels.

Though there were different percentages of mice activity throughout the seasons, the differences were

only found significant between November 2017 and April 2018 (two tailed paired t-test: t 14=-3.83,

P<0.0125) and November 2017 and November 2018 (two tailed paired t-test: t14=-5.29, P<0.0125).

April 2018 had the highest percentage of mice activity with an average of 67.5% of the activity on the

tracking tunnel cards being from mice (Figure 12). In April 2019, 65% of the total activity found on

the tracking tunnel cards in Millennium A and Millennium B tracking tunnel transects were from

mice. No mice were found in November 2018 (Figure 12).

Nov. 2017 Apr. 2018 Nov. 2018 Apr. 20190

10

20

30

40

50

60

70

80

90

Tracking Tunnel Transect by Year

Perc

enta

ge o

f Mic

e pe

r Tra

nsec

t

Figure 12. Percentage of mice (Mus musculus) per transect in the Millennium Forest and Triangle Forest, Waipoua Forest, Northland, New Zealand by year, November 2017 to April 2019. The Triangle Forest tracking tunnel transect is represented in black, the Millennium A tracking tunnel transect is represented in light grey and the Millennium B tracking tunnel transect is represented in dark gray.


24

In both Millennium A and B transects, an average of 65% of tracking tunnels per night had mouse

activity, an average of 37.5% of tracking tunnels per night had rat activity and no tunnels had stoat or

hedgehog activity (Figure 13). In the Triangle Forest, an average of 2.5% of tracking tunnels per night

had stoat and hedgehog activity, but no tracking tunnels had mice or rat tracks. No possum tracks

where found on the tracking tunnel cards, but there was evidence of possum predation on dead kauri

snail shells (Figure 13).

mice rats

stoa

ts

hedg

ehog

mice rats

stoa

ts

hedg

ehog

mice rats

stoa

ts

hedg

ehog

Triangle Millennium A Millennium B

0102030405060708090

100

Mammal and Transect

Activ

ity In

dex

Figure 13. Activity index per mammalian species per forest type (Millennium Forest or Triangle Forest) from 13/04/2019 to 17/04/2019. The Triangle Forest tracking tunnel transect is represented in the first group of mammals, the Millennium A tracking tunnel transect is represented in the middle group of mammals and the Millennium B tracking tunnel transect is represented in the last group of mammals.


25

3.5 Comparison of 2018 and 2019 Data

The Triangle Forest consistently had more alive P. busbyi individuals found during the nocturnal

survey than the Millennium Forest with 263 found in April 2018, 121 found in November 2018 and

207 found in April 2019 (Figure 14). Of the three seasons, April 2018 had the highest number of live

snails with a total of 332 snails, 263 of which were newly found and 69 which were recaptured

(Figure 14). April 2019 had the highest number of live snails found in the Millennium Forest with

nine snails (Figure 14).

Triangle Millennium Triangle Millennium Triangle MillenniumApr. 2018 Nov. 2018 Apr. 2019

0

50

100

150

200

250

300

350

400

Forest Site Over Time

Num

ber

of S

nails

Fou

nd

Figure 14. Comparison of the number of alive snails found, alive snail recaptures, empty shells found and empty shell recaptures in the Triangle Forest and the Millennium Forest, Waipoua Forest, Northland, New Zealand by year, April 2018 to April 2019. Empty shells are represented by the lightest grey, alive shells are represented by light grey, alive snail recaptures are represented by grey and empty snail recaptures are represented by dark grey.


26

Considering April 2018 was the first time conducting the nocturnal surveys, no snails found in older

seasons were recaptured, but 69 snails found that season were recaptured (Figure 15). Of the 250 live

snails found in April 2019, 64 were recaptured at least once during the nocturnal surveys and 29 snails

were recaptured from previous seasons (Figure 15).

Triangle Millennium Triangle Millennium Triangle MillenniumApr. 2018 Nov. 2018 Apr. 2019

0

10

20

30

40

50

60

70

80

90

100

Figure 15. Comparison of the number of alive snail recaptures and empty shell recaptures in the Triangle Forest and the Millennium Forest, Waipoua Forest, Northland, New Zealand by year, April 2018 to April 2019. New snails found that were recaptured in that season are represented in grey while snails that were marked in earlier seasons and recaptured in another season are represented in black.


27

Three diurnal quadrats were taken in both the Millennium Forest and Triangle Forest in April 2018,

totaling six surveyed quadrats; two diurnal quadrats were taken in the Triangle Forest and Millennium

Forest in November 2018 and April 2019. In the Millennium Forest, three live snails were found in

April 2018, five live snails were found in November 2018 and two live snails were found in April

2019 (Table 3). In the Triangle Forest, 16 live snails were found in April 2018, 14 live snails were

found in November 2019 and eight live snails were found in April 2019 (Table 3).

Table 3. Number of empty shells and alive P. busbyi found during the diurnal quadrats in the Triangle Forest and Millennium Forest, Waipoua Forest, Northland, New Zealand from April 2018 to April 2019.

Year Month Forest Quadrat Empty Shells Alive Snails

Total

2018 April Millennium A 4 3 72018 April Millennium B 1 0 12018 April Millennium C 4 0 42018 April Triangle A 9 4 132018 April Triangle B 7 8 152018 April Triangle C 1 4 52018 Novem-

berMillennium A 6 4 10

2018 Novem-ber

Millennium B 9 1 10

2018 Novem-ber

Triangle A 7 5 12

2018 Novem-ber

Triangle B 5 9 14

2019 April Millennium A 4 2 62019 April Millennium B 5 0 52019 April Triangle A 3 8 112019 April Triangle B 5 0 5


28

Over the past three seasons in the Triangle Forest, a total of 696 snails have been found during the

nocturnal surveys, 332 found in April 2018, 124 found in November 2018 and 240 found in April

2019 (Table 4). Over the past three seasons in the Millennium Forest a total of 15 snails were found

during the nocturnal surveys, six were found in April 2018, zero were found in November 2018 and

nine were found in April 2019 (Table 4).

Table 4. Number of empty shells and alive snails found per transect in the Triangle Forest and Millennium Forest, Waipoua Forest, Northland, New Zealand during the nocturnal surveys from April 2018 to April 2019.

Year Month ForestTran-sect

Empty Shells Alive Snails Total

2018 April Millennium 1 0 2 22018 April Millennium 2 1 3 42018 April Millennium 3 4 1 52018 April Triangle 1 9 127 1362018 April Triangle 2 4 160 1642018 April Triangle 3 3 45 482018 November Millennium 1 9 0 92018 November Millennium 2 7 0 72018 November Millennium 3 4 0 42018 November Triangle 1 5 47 522018 November Triangle 2 11 51 622018 November Triangle 3 3 23 292019 April Millennium 1 5 0 52019 April Millennium 2 3 6 92019 April Millennium 3 1 3 42019 April Triangle 1 6 70 762019 April Triangle 2 4 153 1572019 April Triangle 3 8 17 25


29

Of the 250 live snails found in April 2019 (semester 1), 10 snails were recaptures of snails that were

marked in April 2018 (semester 1) or November 2018 (semester 2) and were found to have increased

more than five millimeters in at least one shell measurement and gained more than three grams in

weight. The snail that has changed the most was number 146, which was marked in April 2018. 146

has gained 13 mm in shell width, 17 mm in shell length, five mm in shell height and 20 grams in

weight (Table 5).

Table 5. Change in snails marked in 2018 that were recaptured in the Triangle Forest, Waipoua Forest, Northland, New Zealand during the nocturnal survey from 11/04/2019 to 17/04/2019.

Snail Year SemesterShell

Width (mm)

Shell Length (mm)

Shell Height (mm)

Weight (g)

144 2019 1 41 50 25 25144 2018 1 31 39 20 12144 change 10 11 5 13146 2019 1 42 53 24 31146 2018 1 30 37 20 12146 change 13 17 5 20155 2019 1 43 50 25 29155 2018 2 37.1 44.6 24.6 18155 change 6 6 1 11206 2019 1 47 61 28 37206 2018 1 40 49 26 25206 change 7 12 2 11209 2019 1 44 53 24 31209 2018 2 36.4 46.8 24.6 22209 change 8 6 -1 9238 2019 1 44 57 26 37238 2018 1 39 49 32 25238 change 5 8 -5 12284 2019 1 47 59 27 33284 2018 1 40 46 25 24284 change 7 13 1 10329 2019 1 30 36 18 11329 2018 2 20.3 25.7 14.6 4329 change 10 10 3 7433 2019 1 31 39 21 14433 2018 2 23.2 28.4 20.3 8433 change 8 10 1 6441 2019 1 38 46 24 21441 2018 2 32.8 40.2 20 15441 change 5 5 4 6


30

For all three seasons, the greatest number of snails were found mobile with a mean of 45.2 snails per

night in April 2018, 19 snails per night in November 2018 and 52.4 snails per night in April 2019

(Figure 16). If snails were not mobile, the majority were stationary with a mean of 19 snails per night

in April 2018, 9.6 snails per night in November 2018 and 15.2 snails per night in April 2019 ( Figure

16). Very few snails were found feeding or mating throughout the seasons, with a high in 0.4 snails

per night feeding and two snails per night mating in April 2018 (Figure 16).

Mob

ile

Stat

iona

ry

Feed

ing

Mat

ing

Mob

ile

Stat

iona

ry

Feed

ing

Mat

ing

Mob

ile

Stat

iona

ry

Feed

ing

Mat

ing

Apr. 2018 Nov. 2018 Apr. 2019

0

10

20

30

40

50

60

Behavior Type Over Time

Mea

n N

umbe

r of

Liv

e Sn

ails

Fou

nd p

er N

ight

Figure 16. Mean number of live snails found per behavior type per night (mobile, stationary, feeding or mating) during the nocturnal surveys in the Triangle Forest and Millennium Forest, Waipoua Forest, Northland, New Zealand in April 2018, November 2018 and April 2019.


31

The weight class with the greatest number of snails varies per year. In April 2018, the greatest number

of live snails were found in the 11-20-gram weight class, in November 2018 the greatest number of

live snails were found in the 21-30-gram weight class and in April 2019 the greatest number of live

snails were found in the 31-40-gram weight class (Figure 17). For all three seasons, the least number

of snails were found in the 51-60-gram weight class (Figure 17).

0-10 11-20 21-30 31-40 41-50 51-600

10

20

30

40

50

60

70

80

Weight of Snails (g)

Num

ber

of S

nails

Figure 17. Total number of alive snails by weight class (grams) from the nocturnal surveys and diurnal quadrats in the Triangle Forest and Millennium Forest, Waipou Forest, Northland, New Zealand from April 2018 to April 2019. April 2018 is represented in grey, November 2018 in represented in light gray and April 2019 is represented in dark grey.

For all three seasons, the highest number of live snails were found in the 51-60-millimeter length

class (Figure 18). Only April 2018 had snails 70 millimeters or greater in length. The largest snail on

record is 89.62 mm in length, found in April 2018 (Figure 18).

10-20 21-30 31-40 41-50 51-60 61-70 70 <0

102030405060708090

Length of Snails (mm)

Num

ber

of S

nails

Figure 18. Number of alive snails by length class (millimeters) from the nocturnal surveys and diurnal quadrats in the Triangle Forest and Millennium Forest, Waipou Forest, Northland, New Zealand from April 2018 to April 2019. April 2019 is represented in dark grey, April 2018 is represented in gray and November 2018 is represented in light gray.


32

4 Discussion

A total of 27 P. busbyi shells (alive and dead) were found during the diurnal quadrats and 276 P.

busbyi shells (alive and dead) were found during the nocturnal transects. Of the 276 snail shells found

during the nocturnal transects, the majority of shells, 250, were found in the Triangle Forest, Waipoua

Forest, Northland, New Zealand. Of the 250 total live snails found in the Triangle Forest, 228 snails

were found on leaf litter. The average number of snails per meter were highest in the middle transect

section, number two, with an average of 1.86 snails. These statistics support many of the formed

hypothesis for this report, such as: the majority of live snails will be found on or under leaf litter,

especially in the Triangle Forest rather than the Millennium Forest due to the greater amount of leaf

litter and better mammalian pest management. Another supported hypothesis was that the majority of

snails would be found in the middle of the transect, section two, due to the edge effects on the forests.

4.1 Diurnal Quadrats and Nocturnal Surveys

4.1.1 Diurnal Quadrat and Nocturnal Survey Comparison

Though both experiments were successful in finding P. busbyi snails, it is apparent that the nocturnal

transects were much more successful in finding a greater number of snails. The diurnal quadrats only

covered an area of 100 meters and the highest number of snails found in one quadrat was nine, in the

Triangle Forest in November 2018. The average number of snails found in the Triangle Forest during

the nocturnal surveys were 0.8 live snails per meter, meaning that an average of 80 snails would have

been found in an area of 100 meters.

Since P. busbyi snails are nocturnal, they spend the night on top of the leaf litter feeding or mating,

while during the day they hide under the litter and sometimes dig themselves slightly into the dirt

(Stringer et al., 2003). Considering the snails hid under materials during the day, finding their shells is

more difficult, but when surveyors observed the forest while snails were active, at night, it was easier

to find the shells because they were above the leaf litter. Due to better exposing of the shell, this

allowed a greater abundance of snails to be found, allowing surveyors to better assess P. busbyi

population density. Walking along a transect also allowed the surveyors to cover more ground, better

representing snail distribution.

4.1.2 Triangle Forest and Millennium Forest Comparisons

Though little is known about P. busbyi, previous studies, along with this current study, it is known

that the snails prefer to live in habitats with leaf litter (Stinger et al., 2002; Stringer and McCartney,


33

2003). Being that the Millennium Forest was planted in 2000, 18 years ago, the forest is still in an

early successional stage of life. Many of the planted species within the quadrats and along the

transects were harakeke (Phormium tenax), mānuka (Leptospermum scoparium), kānuka (Kunzea

ericoides) and coprosma (Coprosma repens). An invasive species, blackberries (Rubus fruticosus),

has also greatly taken over the area, covering the walking path for the tracking tunnels and nocturnal

survey transects, though contractors did spray a pesticide on this plant in some areas. The ground was

composed mostly of dense grasses and dirt; all nine live kauri snails found in the Millennium Forest

during the nocturnal transects were found on grasses. The Triangle Forest is a much older age, but an

unknown age, composed of supplejack (Ripogonum scandens), tree fern (Cyathea spp.), lancewood

(Pseudopanax crassifolius), Nīkau palm (Rhopalostylis sapida), and epiphytes. A large majority of

the ground is covered in dense leaf litter or course woody debris. P. busbyi use leaf litter substrate to

hide from bird predation, pig foraging, mammalian predation and for the shade in order to better keep

moisture in their shells (Beauchamp, 2011; Stringer et al., 2002). Therefore, it would be more likely

to find a higher abundance of snails in the Triangle Forest rather than the Millennium Forest.

4.1.3 Paryphanta busbyi Total Abundance throughout the night per 30 minutes

From previous studies, it is understood that P. busbyi snail activity begins after sundown (Parrish et

al., 1995). From 19:10-00:00 the lowest amount of recorded snail activity, 17 live snails found in a

30-minute time frame, was an hour after sundown, in the 19:00 to 19:30 time frame. From 19:31 to

21:30, the total number of snails found generally increased in number, starting with 20 found snails

from 19:31 to 20:00 and ending with 27 found snails from 21:01 to 21:30. This shows that snail

activity is greatest three hours after sundown. After 21:30, the total number of snails found per 30

minutes decreased. Considering P. busbyi evolved isolated in the New Zealand context with the

absence of mammalian predators, nocturnal activity may have been advantageous when birds were

their primary predator. Post human-settlement, the snails have become highly susceptible to nocturnal

mammalian predators who hunt when the snails are exposed above the leaf litter. This can be very

detrimental to the P. busbyi population considering several empty shells found within the Millennium

and Triangle Forest during the nocturnal surveys had evidence of mammalian pest predation.

4.1.4 Triangle Forest Transect Sections

Edge effects are characterized by greater fluctuations in weather conditions that can impact 50 meters

into a forest. These changes can be, but are not excluded to differences in: light exposure, wind and

temperature (Waikato Regional Council). Considering the Triangle Forest is small in size, a good

portion of the forest is impacted by an edge effect, effecting the first and last 50 meters of the 600-

meter nocturnal survey transect. During the nocturnal survey within the Triangle Forest, an average

number of 1.87 snails per meter were found in transect section 2 (200 to 400 meters), compared to the


34

first and third transect segments which had an average of 0.495 and 0.085 snails per meter. Since less

snails were found in the transect sections that would be effected by the edge effect, it is possible that

the edge effect has an impact on P. busbyi population distribution.

4.2 Snail Shell Measurements

Though only five snails were found in the 10-20 millimeter length class and 15 snails were found in

the 21-30 millimeter length class, it is important to see some portion of live Kauri snails within

smaller length classes. This can provide evidence that P. busbyi snails are reproducing and working

towards regenerating their population within both the Millennium and Triangle Forest. It is predicted

that snails become sexually mature when their shell reaches about 40 mm in length, but to determine

whether the reproductive organ has formed would involve killing the individual, which was not the

goal on this experiment considering the snails are at risk of more rapid population decreases (Stringer

and Montefiore, 2000). It is known that once an individual reaches a shell 40 mm in length, the shell

can still grow another 20 mm before forming a hard aperture lip (Stringer and Montefiore, 2000).

With this, snails may become sexually reproductive before gaining their adult shell, giving lots of

hope for the future of the P. busbyi population in the Waipoua Forest, especially since 184 live snails

between the Triangle Forest and Millennium Forest have shells 40 mm or more in length.

In terms of predation, having snails of smaller length classes is also important for population

regeneration. Larger sized shells are also more likely to be preyed upon because they are easier to see,

rather than small shells which live underground and hide better in leaf litter (Beauchamp, 2011).

Larger shells also provide more food and nutrients for mammalian predators making them a target,

giving juvenile snails and smaller length shells more significance in the progression of the P. busbyi

population.

4.3 Tracking Tunnels

4.3.1 2019 Mammalian Activity

Of the three-tracking tunnel transects, the Millennium Forest had the highest pest activity with a mean

of 65 mice and 37.5 rats. The Triangle Forest had relatively less mammalian predator tracks, with a

mean of 2.5 stoat and hedgehog tracks. Though there was no evidence of possum tracks on the

tracking cards, considering the tunnels are not meant for possum tracking, many dead kauri snail

shells showed evidence of possum predation in the Triangle Forest. Possum predation can be

determined when the shell is empty and the flattened spiral on the shell was pushed in. Most shells in

the Millennium Forest showed evidence of rodent predation, which can be determined when the

whole outside of the shell is chewed or the shell is broken into several pieces (Appendix Figure 19;


35

Bennett, Standish and Stringer, 2002). Being that the Millennium Forest had higher mammalian pest

activity, this also supports the hypothesis that more snails would be found in the Triangle Forest

rather than the Millennium Forest. Due to the lack of trapping in the Millennium Forest, this could be

a reason for the low number of P. busbyi being observed during the diurnal quadrats and nocturnal

transects. Most of the Waipoua Forest Trust’s pest management has been put towards trapping in the

Triangle Forest, giving Kauri snails a greater rate of survival in the older growth forest.

4.4 Comparisons Between 2018 and 2019

4.4.1 Paryphanta busbyi Abundances

Throughout the three seasons, April 2018, November 2018 and April 2019, weather conditions have

changed drastically from a wetter season in April 2018 to a drought in April 2019. In this time frame,

in the Triangle Forest, a total of 734 live Kauri snails have been found during the nocturnal surveys

and diurnal surveys, 348 found in April 2018, 138 found in November 2018 and 248 in April 2019.

From a La Niña event that occurred for the first three months of 2018, April 2018 was seen a wet

season for New Zealand, filled with lots of rain fall and high ground moisture (NIWA, 2018). P.

busbyi prefer moist habitats to keep moisture within their shells and promote the emergence of

worms, their prey, from the soil (Parrish et al., 1995). Due to the high amount of ground moisture, it

is reasonable that more snails would emerge from leaf litter to feed, giving a reasonable explanation

for why the most snails were found in April 2018. Further supporting this, the number of observed

snails on dry nights in April 2019 was much less than snails observed on wetter, or rainy, nights.

4.4.2 Mice Activity Over the Years

Though the P. busbyi population was the highest in April 2018 in the Millennium Forest, mice

predation was also the highest during this year with an average of 67.5% of total mammalian activity

recorded on the tracking tunnels cards in the Millennium Forest coming from mice. The high

abundance of mice and rats could have been the reason that the P. busbyi population decreased from

April 2018 to November 2018. Surveyors in November 2018 found four less snails than in April

2018, decreasing from a population of nine live snails in April 2018 to five live snails in November

2018. Due to the high abundance of rodents found in April 2018, the Waipoua Forest Trust funded an

extensive poisoning project in the Millennium Forest and Triangle Forest to reduce mouse, rat and

possum populations. Two lines in the Triangle Forest and several random lines in the Millennium

Forest of bait stations were nailed to trees and hand filled with brodifacoum by volunteers in the

middle of 2017. Volunteers would randomly check and refill the containers when they were available.

In September 2018, the lines were contracted out and all stations were filled and monitored regularly.

This effort resulted in the successful control of the mice population, as seen in November 2018 when


36

no mice were found in the Millennium A or Millennium B tracking tunnel transects. Since the Trust

wants to see an increase in P. busbyi population size, controlling rodent populations is a good step

considering rodents could be causing a decrease in the snail population. The poisoning effort did not

control mice populations for long though because an average of 65% of mammalian activity found on

the tracking tunnel transects in the Millennium Forest in April 2019 were from mice. Rodent

populations within the Millennium Forest was regenerated from outside areas.

Between November 2018 and April 2019, P. busbyi population did increase by six live snails for a

total of 11 live snails found in April 2019. Increases or decreases in populations sizes of the snails

could have been from a number of factors, such as seasonal fluxuations. Data has only been collected

once during the spring season, November 2018, but twice in the fall, April 2018 and April 2019.

However, continuation of pest control within the Millennium Forest could be beneficial and should be

encouraged.

4.5 Further Improvements

When conducting the nocturnal surveys within the Triangle Forest, the transect was split up into three

sections, transects one (0 meters to 200 meters), transect 2 (200 meters to 400 meters) and transects 3

(400 meters to 600 meters). In April 2019, transect 3 was only observed one night, 16/04/2019.

Transect three has only been properly observed once, this beginning in November 2018. Moving

forward with this project, it would be more advantageous for transect three to also be covered as often

as transect one and transect two, giving surveyors and the trust a more general understand of snail

abundances and distributions.

Finding a better way to determine age class would also be beneficial to the study. In determining

whether a snail was an adult or a juvenile, the aperture lip was examined, adults had a hard lip while

juveniles had a softer lip that bent when being pressed upon. During the study, it was found that two

snails, deemed as juvenile due to their soft aperture lip, were mating. In order to make this experiment

more accurate, a different way of determining age class for P. busbyi should be explored. It is also

noted that snails reach maturity at three years of age (Parrish et al., 1995; Stringer and Montefiore,

2000). Finding a way to determine age of the snails would better show whether or not the snail is a

juvenile or an adult. It has been hypothesized that snails reach maturity around 40 mm in shell length,

but the only way to prove this is to kill species of the endemic and at-risk P. busbyi species to observe

their reproductive organ (Stringer and Montefiore, 2000). One suggestion could be keeping snails in

captivity to see how they interact with other snails and grow over time.

4.6 Conclusion


37

Over the past year, April 2018 to April 2019, P. busbyi abundances within the Triangle Forest and

Millennium Forest, Waipoua Forest, Northland, New Zealand have to observed and documented.

April 2019 data alone supports that more snails would be found in the Triangle Forest than the

Millennium Forest due to thicker leaf litter layer from trees of later succession. Kauri snails seem to

be impacted by edge effects and prefer to live in the center of the forest, supported by data on mean

number of snails per meter found per transect section. Findings of live snails with smaller shell

lengths also provides evidence that the snails are mating and increased population is possible within

the two forests. Though it is possible, but not certain, that rodent populations are impacting P. busbyi

populations, the Waipoua Forest Trust has the data necessarily to show that extensive poisoning and

trapping operations did control rodent populations and could possibly promote an increase in the snail

population. Overall, it is expected that the P. busbyi population will increase in the Millennium Forest

with continued growth and succession of the forest.


38

Acknowledgements

First, I would like to thank Shelley Langton-Myers, an EcoQuest academic and the coordinator of this

project, for creating the methods the group used to assess P. busbyi and mammalian pest abundances.

The work completed at in the Waipoua Forest Trust involved many people that were not mentioned as

an author in this report. This work would not have been completed without the Georgie Read of the

Waipoua Forest Trust and members of Te Roroa, Snow Tane and Courtney Davis, for inviting us onto

their land. I would also like to thank workers of the Native Forest Trust, James McLaughlin and Alana

McCloud, for letting EcoQuest members live in their office space for the week of data collection and

making the group feel at home. Lastly, I would like to thank Warren Agnew for donating the Black

Trakka tracking tunnels and Gotcha Traps LTD Tracking Tunnel cards to this research project. Lastly,

I would like to thank EcoQuest for giving me this experience in New Zealand and my fellow Eco-

Quest colleagues and group members who conducted field work with me: Bronwen Bennett, Kendall

Gray, Olivia Regnier, Ramon Balderas and Zoe Spett.


39

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41

Appendix 1

Figure 19. Diagram of a Paryphanta busbyi watti shell after being attacked by a rat, sketch from (Stringer and Montefiore, 2000).


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