Wednesday, May 22, 2013

Pygmy killers and dwarf sperm whales

Over the past week, the easterly Trade winds have diminished in strength to more or less negligible wind speeds. This allowed us to head north on the leeward side of the Big Island in Hawaii for three consecutive days. Sadly, the melon-headed whales were nowhere to be found. Indeed, they were not alone in appearing scare - our sightings have been limited to one or two species each day.

Nevertheless, in spite of the apparent paucity of odontocete cetaceans in Hawaii at present, we have still managed to see some interesting species, even if they have appeared less excited by our presence than us theirs. On one of our forays north we encountered a small group of pygmy killer whales (Feresa attenuata). These small cetaceans are called pygmy killer whales because of some physical similarities, in addition to sharing a taxonomic Family. They typically avoid humans, and eat cephalopods and fish. They also look superficially similar to melon-headed whales - and indeed upon encountering them we hoped that they would turn out to be melon-headed. Sadly, they were not.

A pygmy killer whale (Feresa attenuata)
(Photo: A. Mooney, NMFS permit # 15530 to CRC)
The following day we switched it up and headed south. Yet there too, cetaceans were scarce. We did happen upon a small group of relatively fast moving dwarf sperm whales (Kogia sima). Similar to the pygmy killer whales, these small sperm whales also share a Family with their much larger relatives, the more well-known sperm whales.

A pygmy or dwarf sperm whale (Kogia spp.)
(Photo: A. Mooney, NMFS permit # 15530 to CRC)
Later that afternoon we encountered a lone Cuvier's beaked whale (Ziphius cavirostris). These are very rarely encountered and are averse to humans, which makes them difficult to approach. Beaked whales are extremely deep divers and spend very little time at the surface. We attempted to deploy a satellite tag, but the whale had other plans, and disappeared after a couple short surfacings. Nevertheless, we were able to snap some good photos.

While we don't know why were have been encountering fewer species (and indeed fewer individuals) than usual over the past week, we suspect it may have to do with a lack of favorable feeding opportunities. If that is the case, we can only hope that key prey items such as fish and squid become more abundant over the next few days, and that our whale encounters increase accordingly.

The elusive Cuvier's beaked whale (Ziphius cavirostris)
(Photo: A. Mooney, NMFS permit # 15530 to CRC) 

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