cetaceans (order cetacea) whales, dolphins and porpoises two kinds of whales and dolphins...
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Cetaceans(order Cetacea)
Whales, Dolphins and PorpoisesTwo kinds of whales and dolphins
Mysticetes= Baleen whalesOdontocetes= Toothed whales, porpoises and dolphins
Killer whales (Orcinus orca)
Distributed world-wideLive in matriarchal groups called pods
Off-shore and inshore pods have different pod structuresSpecialize in their feeding habits & hunt in groupsLife expectancy of 30 and >50y for males and femalesSexual dimorphism – males larger, up to 10m w/ 2m dorsal finGestation 17mo, then nursing for 18mo, high infant mortalitySexual maturity at 10-15 w/ adolescent periodMenopause in females at ~40y
Distribution of Killer Whales in N PacificKrahn, M.M., et al. 2002. Status review of Southern Resident killer whales (Orcinus orca) under the Endangered Species Act. U.S. Dept. Commer., NOAA Tech. Memo. NMFS-NWFSC-54, 133 p.
(available off the class web)
Offshores & Transients
N. Pacific Orca Dynamics
Communities, superpods, pods, subpods found all along coast from PS to Arctic Average size is ~150 individuals for a
community Best guess of 1000-1250 Killer whales
in Eastern N Pacific Communities in Price William Sound and
our Southern Residents well studied Northern residents less well studied Echolocation clicks are repeated (pulsed)
sounds in the 1 to 10 Khz range
Salish Sea Orca History
No wide-spread hunting by native Americans
Tribal stories for orca creation propose them to be human (in many instances)
‘hunted’ by military along with seals and sea lions in PS, 1945-1967
Aquarium trade capture 1965-1972
4 Sympatric Communities
Offshores
Transients
Northern Residents
Southern Residents
Differences in dorsal fins
Killer Whale Discrete Calls
Discrete dialects (acoustic clans) that are semi-stable through time SR’s have 1 clan, NR 3 and SAR 2
Time
Fre
quen
cy (
Hz)
Ecolocate, sing & whistle
echolocation
singing
whistle
Lets look at each group
Transients
Communities Found all along Americas, Arctic to Antarctic More abundant in colder water
Feed on other marine mammals Pod structure is small and inclusive of members of either sex ‘lone bulls’ live outside of pod structure Morphological differences
Fin shape, animal size Acoustic differences Actively avoid the fish-eaters Unpublished genetic data suggests
divergence >10,000ybp, unique ‘species’ In PS, @25 individuals in <10 pods
ID’d from ~175 known individuals Attempt to watch Video
Recent Transient Hunting
A pod of transients were in Hood Canal for 2 mo last winter (Jan-Feb 2003)
Take of ~600 seals, roughly half the population T14, one of the whales in the transient pod,
was captured in Hood Canal in the early 1970’s for the aquarium trade, then subsequently released after a public outburst against the captures. If retained, he would have been the only transient ever studied in an enclosed aquarium
Hunting video
This video taken off the Ca coast in 1998, similar feeding strategy used by transients when they were in PS
Offshore Community
Only ‘discovered’ in early 1980’s Least information for these individuals
since they rarely come in shore Appear to live further offshore than the
continental shelf (>70km) 200+ individuals Observed as far south as S. California Genetically similar to southern residents
in their maternal lineage (mtDNA), and fin structure is similar too, but these two groups have never been observed together
Thought to be fish-eaters
Offshore encounter
A group of offshores was observed on May 1st, 2003 in Haro Strait
Northern Community
200+ individuals (up from ~110 in 1965)
8.5% population decline since 1997
Gulf Islands to Queen Charlotte Island
Most similar echolocation, acoustics, pod structure, etc. to southern residents, but not known to regularly interact with southern residents
The Southern Residents
3 (4) pods in the community J,K and L Pods (L-10 subpod) Salmon (90%) of diet
Known to take mammals and other fish on occasion J-pod year-round in Salish Sea
Usually winter in PS, rarely observed outside of Salish Sea K and L pods go offshore Dec-May
Observed both N and S Return within a week of each other usually Reunion of three pods includes ‘singing’ and rubbing Return precedes local salmon runs by 1-2 weeks
Southern Residents
Use top and bottom of water column
Dives are deep and direct Calving interval ~5yrs (0-12) 1950’s population ~125
individuals …despite random target
practice & bad reputation …aquarium trade took ~45
individuals from the population between 1964-1972
Pod Structureof residents and off-shores
Matrilines brothers and
sisters swim together Breeding occurs cross-matrilines
If one pod is male-poor, the other pods could potentially suffer
If one pod loses its females, that pod will go extinct
Washington
Vancouver Island
British Columbia
Summer distribution of southern residents
Genetic studies:
Hoelzel et al. 1991, 1998, Barrett-Lennard 2000
Discrete population that is genetically distinct from the northern resident population in B.C.
SR usage of Haro Straits region
J pooled K pod L pod
Data analysis by Donna Hauser, data from the international sighting network
J Pod Movement Sequences (Summer 2001)
Committed
Turn around
Back/Forth
50/50
Data analysis by Erin Heydenreich, data from the international sighting network
Clockwise movement common
Molecular studies
Mitochondrial DNA analyses (not shown) link maternal lineage of offshores to the residents
Microsatellite data (shown at right) separates residents from other KWs
More N&SR’s Most well known whales in the world SRs did not adopt
Springer in 2002 Luna still in Nootka Sound
“Fearing that a lonely killer whale could injure or kill someone, a team of Canadian authorities and scientists is debating the whale's fate, while police are cracking down on people who pet the creature. The three-and-a-half year-old orca, nick-named Luna, is "pathologically social," says marine biologist Lance Barrett-Lennard of the Vancouver Aquarium in this west coast Canadian city.”
NR’s creating new pods, SR’s might be One expatriate, Lolita, still alive and
living in Florida
Lolita
Last living capture from the Southern Residents
Currently at Sea World, Florida
Current SR population tally
Is the population rebounding from its most recent decline?0
20
40
60
80
100
120
1970 1975 1980 1985 1990 1995 2000 2005
Year
# in
SR
Po
pu
lati
on
Current pressures
Food availability & carrying capacity
Pollution Noise Organic contaminants
Popularity Population size and the Allee effect
Complicated by pod structure and breeding profiles
Let’s focus on this last theme
Excerpted and updated from:
Dynamics of small populations
A presentation provided by:
Paul R. WadeNational Marine Mammal Laboratory
Alaska Fisheries Science Center
NOAA Fisheries
Seattle, WA
The dynamics of small populations become different from large populations
Small populations are at risk of extinction Naturally rare populations exist that appear
stable (e.g., vaquita, Carrribean monk seal) Populations driven to low numbers by human-
caused factors harvest bycatch habitat degradation
Small Populations are the focus of ecological study because of conservation and endangered species issues
Stochastic demographic and genetic factors determine the minimum size of a viable population
3 demographic factors demographic stochasticity environmental stochasticity catastrophes
Populations driven to low numbers face a riskof extinction just from being a small population
Depensation/Allee effects critical density below which the population is
likely to go extinct (in a probabilistic sense) Stochastic population dynamics
Demographic and environmental variance can cause a small population to go extinct just from chance alone
Causes of Allee effects
Genetic inbreeding and loss of heterozygosity inbreeding depression -- expression of deleterious recessive
alleles loss of diversity through drift -- drift occurs much more rapidly in
small populations Behavioral/demographic causes such as a reduction in cooperative
interactions Shortage of fertilization or mating opportunities anti-predator strategies become inefficient in small groups of prey
Allee effect from mating strategy
Whales generally remain in the pod they are born in for life (or at least 27 years)
Males mate outside of pod Lack of males in other pods could lead to
reduced fecundity in a pod if mating strategy is followed strictly
0.000
0.010
0.020
0.030
0.040
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Population level (as fraction of K)
Pop
ulat
ion
gro
wth
per
cap
ita(n
umbe
rs o
f ani
mal
s/po
pula
tion
size
)
Allee effect
No Allee effect
Allee effect
Allee effects
Difficult to study small sample sizes need population growth at different population
levels to detect (“contrast”) historical/retrospective analysis important but
difficult to interpret Meta-analysis found evidence of
Depensation in some fish stocks
PVA estimates for the extinction of SR
Full record, no catastrophes Full record, 2% catastrophe
1992-2000 record, no catastrophes 1992-2000 record, 2% catastrophe
PVA estimates for the extinction of SR
NOAA NMML PVA runs suggest that a single tragedy of major proportions (Exxon Valdez) could wipe out the SR population
What about variability in survival or birth rates?
Both survival (shown at right for old males) and fecundity (bottom right) show periodicity over the last 30 years
0.90
0.91
0.92
0.93
0.94
0.95
0.96
0.97
0.98
0.99
1.00
1973 1977 1981 1985 1989 1993 1997 2001
Year
Sur
viva
l 6 year model Annual
Environmental variance in survival
Hard to predict fate of a particular population2 populations of pinnipeds harvested to very low levels
Northern elephant seals returned from ~100 to more than 80,000
Japanese sea lion (sub-species) went extinct
Demographic stochasticity (N=78)
0
50
100
150
200
250
2000 2020 2040 2060 2080 2100
Year
Pop
ulat
ion
size
0
500
1000
1500
2000
2500
2000 2020 2040 2060 2080 2100
Year
Pop
ulat
ion
size
Demographic stochasticity (N=800)
Some rules of thumb
~50 individuals allows a population to escape from risk of extinction from demographic variance (in the absence of Allee effects)
~500 effective population size allows a population to escape genetic inbreeding problems
In populations of modest size, environmental variance perhaps much more important than demographic
Recent recognition that “catastrophic” events or longer term regime shifts may be more important than inter-annual variation
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