Recent Changes in Body Size of the Eurasian Otter <Emphasis Type="Italic">Lutra lutra</Emphasis> in Sweden |
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Authors: | Yoram Yom-Tov Anna Roos Peter Mortensen Øystein Wiig Shlomith Yom-Tov Thrine M Heggberget |
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Institution: | (1) Department of Zoology, Tel Aviv University, 69978 Tel Aviv, Israel;(2) Department of Contaminant Research, Swedish Museum of Natural History, 104 05 Stockholm, Sweden;(3) Department of Vertebrate Zoology, Swedish Museum of Natural History, 104 05 Stockholm, Sweden;(4) National Center for Biosystematics, Natural History Museum, University of Oslo, POB 1172 Blindern, 0318 Oslo, Norway;(5) Norwegian Institute for Nature Research, 7485 Trondheim, Norway |
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Abstract: | We studied geographical and temporal body size trends among 169 adult museum specimens of the Eurasian otter (Lutra lutra) collected in Sweden between 1962 and 2008, whose sex, year of collection, and locality were known. Skull size and body mass
increased significantly in relation to the year of collection, and skull size (but not body mass) was significantly and negatively
related to latitude, contrasting Bergmann’s rule and the trend found for Norwegian otters. Latitudinal differences in body
size between the two countries may be due to differences in food availability. The temporal increase in body size among Swedish
otters resembled that observed for Norway otters, though Swedish otters are smaller with respect to their Norwegian counterparts.
Latitude and year represent a combination of environmental factors, including ambient temperature in the year of collection
as well as the number of days of ice coverage. We replaced the above factors with mean annual temperature or the number of
days of ice coverage, and found that each of these factors explains a similar proportion of the variation in body size as
did latitude and year. We hypothesize that this temporal increase in body size is related to a combination of factors, including
reduced energy expenditure resulting from increasing ambient temperature, and increased food availability from longer ice-free
periods. |
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Keywords: | Eurasian otter Lutra lutra Sweden Body size Ambient temperature Ice coverage Food availability Global warming |
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