Wednesday, May 15, 2013

Found: melon-headed whales

The leeward side of the Big Island of Hawaii is home to many species of toothed whales and dolphins, but the bottom topography is not uniform. As such, different species are found in different areas along the coast (and some are found further offshore). For two days in a row, the wind was coming from a favorable direction (east) and was sufficiently low to allow us to head north to explore a shelf of around 300-600 m depth where we often find melon-headed whales. True to form, we found them, confirming our hypotheses about their habitat, which are based on the records from satellite tags that have been deployed by air gun over the past several years.
An acrobatic display by a melon-headed whale, sufficiently far from the boat so as not to risk being tagged (Photo: A. Mooney, NMFS permit # 15530 to CRC)

Melon-headed whales are rather small and don't particularly like being approached by the boat. They are often found in large groups, and when we do encounter a group of around 300 individuals, which is not uncommon, we are typically able to find some cooperative animals to get close to in order to deploy additional satellite tags and our suction-cup DTAGs. However, in the last couple days we've found small groups (around 20-40 individuals) and none of them appeared to be particularly keen to be tagged.
A small group of melon-headed whales ((Photo: A. Mooney, NMFS permit # 15530 to CRC))

So instead, we deployed the towfish to make some acoustic recordings while attempting to satellite tag the most cooperative individuals by air gun. While we were unsuccessful in achieving the latter, we did manage to record a range of clicks produced by some of the whales.

Today the wind is likely to have picked up, so it may be that we head south in search of some other species. We hope to head north again as soon as possible.

Squid biologist Dr. Mooney inspecting a piece of squid collected from the surface. Whales foraging on squid at depth often do not consume the entire animal, which results in some parts of the squid floating to the surface. We collect all squid remains to have them genetically tested, in order to determine what species of squid are found in Hawaiian waters (Photo: M. Kaplan)

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