Friday, May 17, 2013

Sperm whales!

We departed the harbor this morning at the typical time of 5:50am. However, given the forecast for big seas and inclement weather we expected that the day would be relatively short. That expectation proved to be unfounded.

The back and dorsal fin of one of the sperm whales
(Photo: A. Mooney,  NMFS permit # 15530 to CRC)
Early sightings of pilot whales and spotted dolphins were cut short when a phone call came in from a local fisherman telling us of the presence of killer whales several kilometers south of our position at the time. Killer whales are rarely sighted in Hawaii - they transit through the area on occasion but do not reside here, and much about where this population goes and what they eat is unknown. So we set out full speed ahead in search of these rarely sighted whales. Nearly an hour later, in relatively calm seas, we had yet to see any additional whales. As our initial excitement at this novel prospect waned, we received yet another phone call with an updated position for the killer whales, in addition to "some other big whales."

Thus, we set off further offshore, our interest yet again piqued and at this point several kilometers away from the Big Island with no land in sight. Shortly thereafter, the so-called "big whales" were sighted by Deron Verbeck, one of our local collaborators, occasional boat driver, and expert in swimming with all variety of Hawaiian cetaceans.

A large sperm whale with the satellite tag (small black object)  attached to the dorsal fin
(Photo: A. Mooney, NMFS permit # 15530 to CRC) 
Indeed, we had happened upon at least 20 sperm whales, including two small calves. The sperm whales (Physeter macrocephalus) are large toothed whales that feed mainly on deep-water squid. They can dive very deep for extended periods of time. Luckily, we found them while they were at the surface and only conducting short, shallow dives. While we had hoped to record some of the sperm whale clicks using our towfish, the encounter was primarily focused on deploying a satellite tag on one of the larger animals. That accomplished, and some sloughed skin retrieved for a suite of molecular investigations, we departed, pleased with finding these impressively large mammals. The day was rounded off with yet another sighting of a large group of pilot whales, perhaps comprised of the two smaller pilot whale groups we had found in the morning.

The weather is supposed to improve markedly over the coming days, and with that we hope to not only continue to encounter the melon-headed whales but to deploy some DTAGs, the primary objective of our work here in Hawaii.

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