Two publications on site fidelity, movements, and association patterns
of two species of poorly-known odontocetes in Hawaiian waters are now available
from the Marine Mammal Science OnlineEarly Articles website. Any subscribers to
MMM can download pdfs through the Online Journal link on the Society for Marine
Mammalogy members website at
www.marinemammalogy.org/members/
For those who are not MMS subscribers or otherwise are not able to download
the papers on-line, please contact me for pdfs. For more information on this
research see
www.cascadiaresearch.org/robin/hawaii.htm
Baird, R.W., A.M. Gorgone, D.J. McSweeney, D.L. Webster, D.R. Salden,
M.H. Deakos, A.D. Ligon, G.S. Schorr, J. Barlow and S.D. Mahaffy. 2008. False
killer whales (Pseudorca crassidens) around the main Hawaiian Islands: long-term
site fidelity, inter-island movements, and association patterns. Marine Mammal
Science 24. doi: 10.1111/j.1748-7692.2008.00200.x
Abstract
Despite their world-wide distribution throughout the tropics and
subtropics, false killer whales (Pseudorca crasssidens) are one of the
lesser-known large odontocetes. Genetic evidence indicates a demographically
isolated population around the main Hawaiian Islands. We examine site fidelity,
movements and association patterns in this population using data from directed
surveys and opportunistic photographs from 1986 to 2007. This species was only
infrequently encountered, and while found in depths from 38 to 4,331 m, sighting
rates were greatest in depths > 3,000 m. We photo-identified 152 distinctive
individuals. Resighting rates were high, with an average of 76.8% of distinctive
individuals within groups documented on more than one occasion. Most (86.6%)
were linked by association into a single association network; only one large
group (16 distinctive individuals) documented the farthest offshore (42-70 km),
did not link by association into that large network, and may be part of an
offshore population. Individual movements of up to 283 km were documented, with
a large proportion of individuals moving among islands. Individuals were
resighted up to 20.1 yr after first being documented, showing long-term fidelity
to the islands. Repeated associations among individuals were documented for up
to 15 yr, and association analyses indicate preferred associations and strong
bonds among individuals.
Baird, R.W., D.L. Webster, S.D. Mahaffy, D.J. McSweeney, G.S. Schorr, and
A.D. Ligon. 2008. Site fidelity and association patterns in a deep-water
dolphin: rough-toothed dolphins (Steno bredanensis) in the Hawaiian Archipelago.
Marine Mammal Science 24. doi: 10.1111/j.1748-7692.2008.00201.x
Abstract
In the Pacific, rough-toothed dolphins (Steno bredanensis) are typically
found in the open ocean and in deep water around oceanic islands. We examine
habitat use, site fidelity, movements, and association patterns of this species
in the main Hawaiian Islands. Sighting rates were highest in depths > 1,500
m. There were frequent within- and between-year resightings off the island of
Hawai'i, indicating a small population size with high site fidelity. Resighting
rates were lower off Kaua'i/Ni'ihau, indicating a larger population size, but
with some site fidelity. Two individuals were documented moving from Kaua'i to
Hawai'i, a distance of 480 km, but were not seen to associate with dolphins off
Hawai'i. Observed movements were consistent with at most 2% dispersal per year
between these two areas. Differences in group size, habitat use, and behavior
imply that movements amond the islands may be limited. Little is known about the
diet of rough-toothed dolphins in Hawai'i, but they are thought to feed
primarily on near-surface species. High fidelity to deep-water areas off the
island of Hawai'i likely reflects an increase in the predictability of prey
associated with upwelling due to the island mass effect, wind stress curl and
cyclonic eddies that form off the island.