With their distinctive snouts and massive bodies, beaked whales such as the Blainville's (bottom), are the kind of marine mammal people notice. Although there are 21 species in the beaked whale family (Ziphiidae, including the Cuvier's beaked whale, top), they're rarely seen and remain one of the most mysterious and least studied of whales. That's largely because they live far out at sea and spend much of their time diving and feeding at depths exceeding 1000 meters. Now, scientists from the National Oceanic and Atmospheric Association Southwest Fisheries Science Center in San Diego, California, have analyzed data from six surveys completed off the Pacific coast from Canada to Mexico over an 18-year period from 1991 to 2008. Their study, reported today in PLOS ONE, provides the first abundance trend estimates for beaked whales—and reveals a disturbing population decline for this group. Neither hunting nor being entangled in fishing nets is causing the drop, the team reports. Beaked whales are known to be stressed by Naval sonar tests and possibly by increasing levels of other human-generated noise from commercial vessels in the oceans. Another concern is the possible loss of squid, which the whales dine on, from oxygen depletion in the deep ocean. Although the scientists were unable to pinpoint the cause of the beaked whales' declines, they have provided the International Union for Conservation of Nature's Red List of Threatened Species with the first population trends for these species.
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*Correction 10:50 a.m., 17 January: The images were misidentified in the original version. The Cuvier's beaked whale is pictured in the top photo; the Blainville's beaked whale is on the bottom.