INCREASED HARASSMENT OF RIGHT WHALES (EUBALAENA AUSTRALIS) BY KELP GULLS (LARUS DOMINICANUS) AT PENÍNSULA VALDÉS, ARGENTINA |
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Authors: | V J Rowntree P Mcguinness K Marshall R Payne M Sironi J Seger |
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Institution: | Whale Conservation Institute, Department of Biology, University of Utah, Salt Lake City, Utah 84112, U. S. A. E-mail:;Whale Conservation Institute, 191 Weston Road, Lincoln, Massachusetts 01773, U. S. A.;Department of Biology, University of Utah, Salt Lake City, Utah 84112, U. S. A. |
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Abstract: | Kelp gulls at Península Valdés, Argentina, have recently developed the habit of feeding on pieces of skin and blubber that they gouge from the backs of southern right whales. In response, the whales flinch violently, submerge, and swim rapidly away underwater. The level of harassment in 1995 was almost five times higher than when first studied in 1984 by Thomas (1988). In 1995, 67% of attacks were aimed at large white lesions on the whales' backs. The proportion of whales with lesions increased from 0.01 in 1974 to 0.32 in 1990. Mother-calf pairs that were attacked traveled at medium and fast speeds for 3.1 h per day, compared to 0.8 h for undisturbed pairs. Mother-calf pairs are estimated to spend approximately 24% of their daylight hours in states of gullinduced disturbance. Little food is available at Península Valdés, so mothers must rely on blubber reserves to support their calves' growth, behavioral development, and migration to the feeding grounds. Even when undisturbed by gulls, mothers often curtail their calves' play and nursing bouts, suggesting that their energy reserves are limited. Increasingly intense harassment by gulls may therefore compromise calf development and might even induce right whales to abandon Península Valdés for other calving grounds. |
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Keywords: | southern right whale Eubalaena australis kelp gull Larus dominicanus harassment Península Valdés |
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