Fourth International Orca Symposium and Workshop - CEBC - CNRS

should be made to archive samples for posterity and great care should be taken to photoidentify
each individual sampled.
The following points were raised in a general discussion. Olesiuk pointed out that the
genetic contribution of males is not reflected in current population models. Since paternal
genetic contribution is likely to influence maternal reproductive success, he suggested that
genetic techniques could reduce the noise in existing models. The question of using genetic
techniques to estimate effective (breeding) population size was raised by Ugarte. Barrett-
Lennard pointed out that conventional methods to directly extrapolate effective population
size from allele frequencies are extremely sensitive to violations of a very restrictive set of
assumptions (such as random breeding, which is known not to prevail in resident killer
whales). Newer methods may improve the precision somewhat, but it is unlikely that
genetics alone will provide a magic bullet for estimating population size. A question was
raised about the conservation implications of mating system analysis. Barrett-Lennard
provided an example. The southern resident killer whale population of British Columbia
contains only three pods. Genetic analysis indicates that mating occurs between, not within
pods (Barrett-Lennard 2000). This means that the females of the largest pods have very few
potential mates---a situation that may be exacerbated by the general failure of young adult
males to father calves. The results suggest that many calves in the next generation may be
sibs and half-sibs, resulting in a rapid loss of genetic diversity.
The possibility of doing a sight – resight population estimates of killer whales using
genotypes instead of photographs was raised. There was general consensus that given the
difficulty, expense, and invasiveness of biopsy sampling, and the expense of analzying DNA,
photographic methods are much preferred for the species. However, it was conceded that in
certain instances with relatively rarely-seen populations it could possibly be used along with
photographic methods.
Naming and Grouping Killer Whales in Field Studies
One of the first problems faced in a new killer whale field study is how to name and
group identified individuals. The workshop participants felt that establishing an efficient,
useful, flexible system early in a project was extremely helpful. Since most studies use the
basic system developed by Bigg and colleagues for resident killer whales, the system is
described below. A second system developed by the same researchers is also described, and
is followed by a general discussion.
Bigg et al. (1990) established a system whereby a unique alpha-numeric code was used
to designate each individual. A single letter designated the whale’s pod (defined as the largest
group in a community that travelled together at least 50% of the time). The letter was
followed by a two-digit number designating the order in which individuals in the pod were
first identified. Thus, A25 was the twenty-fifth individual identified in A pod. Several years
after this naming system was established, some of Bigg’s initial pod designations were shown
to be incorrect. For example A pod in fact comprised three pods. Each of the “revised” pods
kept the A-designator, but was given a name based on the most distinguishable individual in
the group. Thus, A25 was reassigned to A5 pod. Recently Ford & Ellis (these proceedings)
showed that pods are less permanent than originally thought and proposed that matrilines, not
pods, be considered the fundamental units of social organisation in resident killer whales. In
sum, although the resident naming system has worked for book-keeping, it does not serve as a
reliable template of resident killer whale social organisation.
FOURTH INTERNATIONAL ORCA SYMPOSIUM AND WORKSHOPS
SEPTEMBER 23-28 2002, CEBC-CNRS, France
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