[MARMAM] New Publication in press: Killer Whale (Orcinus orca) Predation on Whales in Sri Lankan Waters.

Georgina L Gemmell georgina.wildoceans at gmail.com
Sun Jun 21 10:20:17 PDT 2015


Dear Marmamers,

On behalf of my co-authors, I am pleased to announce a new publication
(Short Note) in press, to be published in the journal Aquatic Mammals.
Gemmell, G. L., McInnes, J. D., Heinrichs, S. J. & de Silva Wijeyeratne, G.
(In Press) Killer Whale (Orcinus orca) Predation on Whales in Sri Lankan
Waters.

If you would like to receive a copy of the In press PDF, please contact
myself (Georgina Gemmell – OPSL Co-Founder and Lead Administrator) at
georgina.wildoceans at gmail.com. The official print version will appear in
the December 2015 issue of Aquatic Mammals Journal, available only to
subscribers.

This short note provides the first insight into the dietary habits of the
little-known killer whale population seen off Sri Lanka, in the Northern
Indian Ocean. Orca Project Sri Lanka, a public-science and Photo ID study
of the local killer whale population, received photographs and footage
documenting two separate attacks on cetaceans in Sri Lankan waters, these
are (1) an attack on a pod of sperm whales (Physeter macrocephalus) and (2)
an attack on a mesoplodont beaked whale (Mesoplodon sp.) In addition to
these accounts, we also present circumstantial evidence of an attack on a
blue whale (Balaenoptera mus¬culus). Among the most significant findings
were the predator and prey strategies observed in account (1): the killer
whales attacked the sperm whales in an apparent wound-withdraw strategy.
All age and sex classes appeared to be involved with the large adult male
killer whale playing a pivotal role, delivering the blow that separated a
smaller sperm whale from the rest of the herd. The sperm whales did little
to defend themselves: their main defensive behaviour was maintaining a
tight group on the surface, at times forming a rosette (or ‘marguerite’-
heads inwards, tails out) - a behaviour which up until now has only been
described from the Pacific and Atlantic Oceans. It is unclear whether any
sperm whales were killed in the attack, but the observation of blood and an
oil slick on the surface suggest that at least one sperm whale had been
injured. Other noteworthy findings include, to our knowledge, the first
record to confirm killer whales preying on mesoplodonts (2), which until
now were only suggested as prey based on scars consistent with killer whale
teeth observed in a beached specimen of M. densirostris. And Account (3),
the first strong circumstantial evidence to support killer whales
opportunistically preying on blue whales in Sri Lankan waters. Overall,
these observations provide crucial insight into the behaviour of this
little-studied killer whale population, and also contribute to the overall
knowledge available for killer whales preying on large cetaceans.

All the best
Georgina Gemmell


-- 
*Georgina Gemmell*
Lead Administrator, Orca Project Sri Lanka
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