[MARMAM] New publication on prey sharing behaviour of resident killer whales

Brianna Wright briannamwright84 at gmail.com
Tue Apr 19 09:06:02 PDT 2016

Dear colleagues,

We are pleased to announce the publication of a new paper on kin-selective
prey sharing behaviour by 'resident' killer whales of the northeast Pacific:

* Wright, B.M., Stredulinsky, E.H., Ellis, G.M., and Ford, J.K.B. 2016.
Kin-directed food sharing promotes lifetime natal philopatry of both sexes
in a population of fish-eating killer whales, Orcinus orca. Animal
Behaviour 115:81-95.*

ABSTRACT: The vast majority of social animals exhibit sex-biased dispersal
as a strategy to reduce kin competition and avoid inbreeding. Piscivorous
‘resident’ killer whales, *Orcinus orca*, of the eastern North Pacific,
however, are unusual in that both sexes remain philopatric throughout life,
forming highly stable, multigeneration matrilines that are closed to
immigration. We conducted a 12-year study documenting extensive cooperative
prey sharing within these matrilines, and hypothesized that extreme natal
philopatry in resident killer whales arose due to inclusive fitness
benefits gained by provisioning maternal kin. We found that prey sharing
was nonreciprocal, and even though whales routinely foraged in mixed
associations containing multiple matrilines, prey sharing among individuals
belonging to different matrilines was very infrequent. Furthermore,
maternal relatedness was a significant predictor of the frequency of prey
sharing between individuals, with close maternal kin sharing more often
than distant relatives or nonkin. Adult females were much more likely to
share prey than adult males or subadults, probably because they mainly
provisioned their offspring. However, food sharing was not limited solely
to maternal care; all age–sex classes engaged in this behaviour by sharing
with close maternal relatives, such as siblings and mothers. We also
investigated the frequency of prey sharing between mothers and their
offspring as a function of offspring sex and age, and found that maternal
food sharing with daughters declined after daughters reached reproductive
maturity, which could help to explain matriline fission events. The
evolution of kin-directed food sharing requires the ability to reliably
discriminate kin, which resident killer whales likely achieve through
social familiarity and vocal dialect recognition. We propose that lifetime
philopatry of both sexes has been selectively favoured in this population
due to the inclusive fitness benefits of kin-directed food sharing, a
cooperative behaviour that may also inhibit dispersal by reducing resource
competition among kin.

This paper is an Open Access publication and is freely available for
download at the following link:
Or a PDF can be provided via email request: Brianna.Wright at dfo-mpo.gc.ca

- Brianna

Brianna Wright, M.Sc.
Marine Mammal Research Technician
Fisheries and Oceans Canada
Pacific Biological Station
3190 Hammond Bay Rd.
Nanaimo, BC V9T 6N7 CANADA
phone: (250) 756-7253
Brianna.Wright at dfo-mpo.gc.ca
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