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New pygmy killer whale study
A new study of pygmy killer whales recently published in the journal Marine Mammal Science shows that those living off Hawaii tend to stay close to the islands and don't swim out to the open ocean. There are very few of the whales, probably less than 200 individuals, in this distinct pygmy killer whale population off the islands. They are encountered so infrequently that any particular population of the species could be dramatically declining without it being documented - one of the problems with very rare species.
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The study was based on an ongoing photo identification project launched in the mid-1980s. Approx 3,431 photos of pygmy killer whales taken over 22 years were examined, finding that most of the whales were spotted off the Big Island, though a few were found off Oahu, Lanai and Niihau. The animals were identified by their body scars, dorsal fin shapes and other distinctive characteristics. |
The study also showed that researchers repeatedly came across the same whales, including one individual who was spotted over a 21-year period. The analysis also showed pygmy killer whales appear to be social animals, with many staying close to other individuals for at least 15 years. Their stable, long-term relationships resemble the social behaviours of killer whales and pilot whales.
Pygmy killer whales are found in tropical and subtropical waters around the world yet they are among the least understood toothed whales, in part because they generally live in the open ocean and so are harder for scientists to study. Hawaii's group is the only known case of a pygmy killer whale population that remained isolated in one area and didn't venture out to the open ocean. On average, the researchers spotted pygmy killer whales about 3.7 miles from Hawaii shores. The furthest offshore being 9.3 miles. It is thought that Hawaii's pygmy killer whales, like Cuvier's beaked whales and almost 10 other whale and dolphin species living in island waters, don't venture far because there isn't much food for them just outside Hawaiian waters. The islands are their most reliable source of food, so they stay nearby.
Hawaii's pygmy killer whales are so rare that they accounted for only 11 percent, of 889 whale and dolphin sightings the researchers made off Hawaii between 2000 and 2007.
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