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The Diving Behaviour of the Platypus (Ornithorhynchus anatinus) in Waters with Different Trophic Status

H. Kruuk
Journal of Applied Ecology
Vol. 30, No. 4 (1993), pp. 592-598
DOI: 10.2307/2404239
Stable URL: http://www.jstor.org/stable/2404239
Page Count: 7
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The Diving Behaviour of the Platypus (Ornithorhynchus anatinus) in Waters with Different Trophic Status
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Abstract

1. The diving behaviour of platypus (Ornithorhynchus anatinus) in their natural habitat is described, comparing performance in waters of different nutrient content. 2. The mean dive time (TUW) was 35 s, but varied between 27 s and 49 s for different habitats. These times were much longer than was predicted from comparisons with other, larger semi-aquatic mammals on the basis of body weight. 3. Mean time on surface (TOS) was 13 s, varying with habitat between 11 s and 17 s; within-habitat variation in TOS was greater than that for TUW, probably related to differences in food processing. 4. There was a low correlation between TUW and subsequent TOS, and no substantial effect of depth on TUW. In the foraging areas with greatest nutrient content and food availability platypus covered longer distances during dives and on the surface. 5. Platypus are multi-prey loaders and it is suggested that the index TUW/TOS can be used to assess foraging efficiency, and to compare the performance of platypus in different habitats. Results suggest that foraging efficiency is increased in eutrophic waters, even at high levels of nitrification and phosphorization, due to greater density of prey.

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