[MARMAM] Recent publication on transient killer whales
Orcamom1 at aol.com
Orcamom1 at aol.com
Fri Nov 5 09:00:04 PDT 2010
Ecological aspects of transient killer whales (Orcinus orca) as predators
in southeastern Alaska
Wildlife Biology, Volume 6, No. 3: 308-322
Marilyn E. Dahlheim, National Marine Fisheries Service, Alaska Fisheries
Science Center, National Marine Mammal Laboratory, 7600 Sand Point Way NE.,
Seattle, Washington 98115. USA. E-mail: _marilyn.dahlheim at noaa.gov_
(mailto:marilyn.dahlheim at noaa.gov/)
Paula A. White, Museum of Vertebrate Zoology, 3101 Valley Life Sciences
Building, University of California, Berkeley, California 94720. USA.
In this study we present empirical data on predator numbers, movements and
area usage, and predation obtained from tracking transient killer whales
(Orcinus orca) throughout the inland waters of southeastern Alaska, USA.
During 1991-2007, we documented 155 transient killer whales via
photo-identification methodology within this large study area (27,808 km2). Transient
killer whales were distributed throughout southeastern Alaska and were
present during all seasons, although not all individuals were seen each year.
Resighting data suggested that within southeastern Alaska, maternal groups
may partition area usage of their environment. By following whales for
1,467 km, we calculated a mean travel speed of 7.2 km/h with mean daily
movements of 134 km ± 88 km/24 hours and ranging within 59-240 km/24 hours.
Photographic matches demonstrated that most (86%) of the transient killer whales
identified in southeastern Alaska also utilized British Columbia and
Washington State waters. In contrast, photographic matches between whales in
southeastern Alaska and whales seen off of California, USA, were rare,
suggesting that different transient killer whale stocks occupy these two
regions. Transient killer whales preyed upon Dall’s porpoise (Phocoenoides
dalli), Pacific white-sided dolphins (Lagenoryhncus obliquidens), harbor porpoise
(Phocoena phocoena), minke whales (Balaenoptera acutorostrata), Steller
sea lions (Eumetopias jubatus), harbor seals (Phoca vitulina), and seabirds.
Potential prey species available, but not targeted, included humpback
whales (Megaptera novaeangliae), elephant seals (Mirounga angustirostris), and
sea otters (Enhydra lutris). Prey-handling techniques varied depending upon
the prey being targeted with no evidence of prey specialization. During
114 encounters totaling 332.5 hours of direct observations of transient
killer whales, we documented 36 predation events for a calculated kill rate of
0.62 prey items/24-hour period/whale. The data we present in this article
provide a foundation of transient killer whale ecology aimed at improving
our ability to understand the impact of transient killer whale predation on
southeastern Alaska prey populations.
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