Harbor Porpoises Can Thank Arch Enemy for Their Success

The harbor porpoise (Phocoena phocoena) is a whale species that is doing quite well in coastal and busy waters. They are found in large numbers throughout the Northern Hemisphere from Mauritania to Alaska, and now researchers from the University of Southern Denmark explain why these small-toothed whales are doing so well: The harbor porpoises can thank their worst enemy, the killer whale, for their success. Coastal areas are more challenging and potentially dangerous for a small whale. There is a risk of beaching and being caught in a fisherman's net, but there are also benefits. Fish are plentiful and easier to find in coastal waters than in the open sea. Therefore, coastal waters are attractive for porpoises, and they are extremely skilled at navigating, locating prey and avoiding hazards near the coast. Like other toothed whales porpoises use echolocation for orientation and to detect prey. They emit a constant stream of sonar clicks, which, when these hit a rock, a fish, or a ship nearby an echo is sent back to the porpoise. From the echo, the porpoise can distinguish the location of the object and often also can identify the object. Porpoises can locate even small fish and small objects such as net floats and fine fishing nets. This ability sets them apart from many other toothed whales, which do not have such sophisticated echolocation abilities. The secret of this ability is that the porpoise uses very short clicks and these are higher in frequency than those of many other toothed whales, explains Dr. Lee Miller from the Institute of Biology, University of Southern Denmark (SDU). Porpoise clicks last just a hundred-millionth of a second, and are about 130 kHz. For comparison, a human can hear up to 20 kHz and a dog up to about 60 kHz. Dr. Miller and his colleague Dr.
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