Saturday, October 04, 2014

A new whale in the Gulf of Mexico?

Whale taxonomy - and taxonomy in general - is still not as precise as scientists would like. Some scientists suggest species in general are more variable than we once thought: some have given up on subspecies and other distinctions. DNA analysis provides a powerful new tool, but there's no universally-accepted rule about what degree of difference, and what kind of differences, clearly delineate separate species or subspecies. 
The latest discovery in cetacean taxonomy is a surprising one. A small population of Bryde's whales (Balaenoptera edeni) in the Gulf of Mexico appears so distinct that it represents, at the least, a new subspecies.
Bryde's whales are among the smaller rorquals - the all-time record is 15.5m long, and most are significantly smaller - and the least known.  This population has unique calls and distinct DNA. Indeed, they seem more closely allied genetically to Pacific Bryde's whales than to Atlantic populations. The nonprofit National Resources Defense Council (NRDC) intends to petition the U.S. Environmental Protection Agency (EPA) to declare the population endangered. 
DNA testing helped determine, in 2003, that what had been thought to be a strain of Bryde's whale was in fact a different species, now known as Omura's whale (Balaenoptera omurai). There are other outstanding questions about classification of apparently differing Bryde's whale populations, including an inshore and an offshore form (see the IUCN writeup here), and it's a good reminder that even the largest creatures on Earth keep some secrets from science.  We have much to learn.

Bryde's whale, showing the distinct ridges around the blowhole (rostral ridges). (Photo NOAA)

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