Divergence in killer whales

Two different types of killer whales Orcinus orca inhabit UK waters, according to an English-Dutch research team.

A study based on morphological aspects, isotopes and genetic analysis provided evidence for differences between two sympatric killer whale kinds (called ‘type 1’ and ‘type 2’).

‘Type 1’ is characterised by eye patch with parallel orientation, worn-out teeth at adult stage, 12 teeth in the lower jaw, and a catholic diet ranging from fish to seals.

‘Type 2’ has eye patch with angular orientation, 11 teeth in the lower jaw and less worn-out, greater body size with adult males almost two metres larger than the other adults, and a more specialised diet, probably focused on whales and dolphins.

"They seem to have occupied completely different ecological niches and have started to diverge morphologically " commented Andrew Foote, leader of the study. Will this divergence bring the killer whales to divide in different sub-species?

Silvia Bonizzoni

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Photo: Adult Type 1 (top) and Type 2 (down) mandibles, by Andrew Foote

Article:
Foote A.D., Newton J., Piertney S.B., Willerslev E., Gilbert M.T.P. 2009. Ecological, morphological and genetic divergence of sympatric North Atlantic killer whale populations. Molecular Ecology 18(24):5207-5217.

For more information:
http://news.bbc.co.uk/earth/hi/earth_news/newsid_8440000/8440002.stm