Cetaceans (order Cetacea): Cetaceans (order Cetacea) Whales, Dolphins and Porpoises
Two kinds of whales and dolphins
Mysticetes= Baleen whales
Odontocetes= Toothed whales, porpoises and dolphins
Killer whales (Orcinus orca) : Killer whales (Orcinus orca) Distributed world-wide
Live in matriarchal groups called pods
Off-shore and inshore pods have different pod structures
Specialize in their feeding habits & hunt in groups
Life expectancy of 30 and >50y for males and females
Sexual dimorphism – males larger, up to 10m w/ 2m dorsal fin
Gestation 17mo, then nursing for 18mo, high infant mortality
Sexual maturity at 10-15 w/ adolescent period
Menopause in females at ~40y
Distribution of Killer Whales in N Pacific: Distribution of Killer Whales in N Pacific Krahn, 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: 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: 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: 4 Sympatric Communities Offshores
Transients Northern Residents
Southern Residents
Differences in dorsal fins: Differences in dorsal fins
Killer Whale Discrete Calls: 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 Frequency (Hz)
Ecolocate, sing & whistle: Ecolocate, sing & whistle echolocation singing whistle
Lets look at each group: Lets look at each group
Transients: 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: 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: Hunting video This video taken off the Ca coast in 1998, similar feeding strategy used by transients when they were in PS
Offshore Community: 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: Offshore encounter A group of offshores was observed on May 1st, 2003 in Haro Strait
Northern Community: 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: 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: 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 Structure of residents and off-shores: Pod Structure of 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
Summer distribution of southern residents: 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: 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): 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: 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: 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: Lolita Last living capture from the Southern Residents
Currently at Sea World, Florida
Current SR population tally: Current SR population tally Is the population rebounding from its most recent decline?
Current pressures: 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: Excerpted and updated from: Dynamics of small populations A presentation provided by:
Paul R. Wade
National Marine Mammal Laboratory
Alaska Fisheries Science Center
NOAA Fisheries
Seattle, WA
The dynamics of small populations become different from large populations: 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: 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 risk of extinction just from being a small population: Populations driven to low numbers face a risk of 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: 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
Slide35: 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
Allee effect: Allee effect
Allee effects: 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: 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: 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?: 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
Environmental variance in survival: Environmental variance in survival
Hard to predict fate of a particular population 2 populations of pinnipeds harvested to very low levels: Hard to predict fate of a particular population 2 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): Demographic stochasticity (N=78)
Demographic stochasticity (N=800): Demographic stochasticity (N=800)
Some rules of thumb: 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