[MARMAM] New paper on dorsal fin shape in Pilot whales
augustojoana at gmail.com
Mon Jan 14 15:29:10 PST 2013
We are pleased to announce the recent publication of the following note on
pilot whale dorsal fin shape:
Augusto, Joana F.; Frasier, Timothy R.; Whitehead, Hal. (2013). Using
photography to determine sex in pilot whales (*Globicephala melas*) is not
possible: Males and females have similar dorsal fins. Marine Mammal Science
29(1): 213-220. doi: 10.1111/j.1748-7692.2011.00546.x
Pilot whales are sexually dimorphic odontocetes. Males are larger than
females and, since dorsal fins growth isometrically with body size, also
possess larger dorsal fins. Males are also thought to have dorsal fins that
are thicker at the edge, with more rounded contour and rounded edge.
The population of long finned pilot whales that summers in the waters
around Cape Breton, Canada, has been studied since 1998. There are
currently more than 2000 individuals photo- identified. If these
individuals could be assigned to sex, the data set would be much more
powerful .We tested whether dorsal fin shape, number of mark points and
saddle patch density are different enough between sexes so they could be
used to predict sex based on photographic data.
We biopsied 18 known individuals from the population and determined their
sex genetically, through PCR of the Zfx and Zfy introns. We used Eliptical
Fourier Descriptor Analysis to determine the most variable parts of the
dorsal fin shape for those individuals, and examined whether the patterns
differed according to sex using a discriminant function analysis and
MANOVA. Saddle patch density was compared across sexes using a permutation
test, and the number of mark points using a Mann-Whitney U test. Eleven of
the sampled individuals were males and seven females. We found that males
and females have similar dorsal fin shape (MANOVA P=0.119), saddle patch
density (P=0.17) and mark point distribution (P=0.23). It does not seem to
be possible to use either dorsal fin shape, saddle patch density or number
of mark points to usefully predict sex of individual pilot whales.
It is available at
Joana Augusto, M.Sc.
B3H 4R2 Canada
Let's Talk Science Coordinator
LTS at dal.ca
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