Recent Changes in Body Size of the Eurasian Otter Lutra lutra in Sweden
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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.
KeywordsEurasian otter Lutra lutra Sweden Body size Ambient temperature Ice coverage Food availability Global warming
Thanks are due to Olavi Grönwall for his warm hospitality to YYT and SYT during their visit to the NRM and to Per Ericson for his valuable support. We are grateful to Eli Geffen for advice and comments, to Naomi Paz for editing this article, and to two anonymous reviewers for their helpful suggestions. YYT and SYT would like to thank Nick Davies for his hospitality during their sabbatical in Cambridge, England. We are grateful to Else-Marie Wingqvist of the Swedish Meteorological Service and to Mark Lomas of Sheffield University for their help in obtaining climate data. We acknowledge the financial support of a SYNTHESYS grant to YYT (SE-TAF-1844) made available by the European Community Research Infrastructure Action under the FP6 Structuring the European Research Area Programme, and the Israel Cohen Chair of Environmental Zoology to YYT.
- Ask, L., and H. Westerberg (eds.). 2008. Fiskbestånd och miljö i hav och sötvatten - Ressurs- och miljööversikt 2008, 180 pp. Fiskeriverket (The Swedish Board of Fisheries) (in Swedish). http://www.fiskeriverket.se/download/18.2cd9c4ad11a113f131a8000100/RoM2008-web.pdf.
- Bister, M., and A. Roos. 2006. Uttern I Sverige 2006. V ärldsnaturfondet WWF, 40 pp (in Swedish).Google Scholar
- Gustafson, L., and I. Ahlen (eds.). 1996. National atlas of Sweden, Vol. 16. Geography of plants and animals. Stockholm: Swedish Meteorological and Hydrological Institute.Google Scholar
- Heggberget, T.M., M.I. Solem, and F. Holmstrøm. 2007. Fallvilt og avlivede dyr av oter - Årsrapport for 2006. [Collected dead otters—annual report 2006]. In Norwegian with English abstract. NINA Rapport. 243.Google Scholar
- Holmquist, C., and O. Funcke. 2006. Vattenbruk i Sverige 2005. Aquaculture in Sweden in 2005. Sveriges officiella statistik, statistiska meddelanden. In Swedish with parts in English. JO 60 SM 0601, 17 pp.Google Scholar
- Johnsen, S. 1928. Rovdyr og rovfuglstatistikken i Norge [Statistics for carnivores and birds of prey in Norway]. In Norwegian - Bergen Mus. Årbok 1929, Nat. vid. Rekke 2:1–118 + Tables.Google Scholar
- Kjønhaug, A.F. 2006a. Produksjon av laks og regnbueørret 2005 [Production of salmon and rainbow trout 2006]. In T. Svåsand, K. Boxaspen, E. Dahl, and L.L. Jørgensen, ed. Norwegian with English summary. In Kyst og havbruk 2006. Fisken og havet, særnr. 2-2006.Google Scholar
- Kjønhaug, A.F. 2006b. Produksjon av torsk 2005 [Production of cod 2005]. In Norwegian with English summary. In T. Svåsand, K. Boxaspen, E. Dahl, and L.L. Jørgensen, ed. Kyst og havbruk 2006.Google Scholar
- Kruuk, H. 1995. Wild otters: predation and populations. Oxford: Oxford University Press.Google Scholar
- Pertoldi, C., A.B. Madsen, E. Randi, A. Braun, and V. Loeskschcke. 1998. Variation of skull morphometry of Eurasian otters (Lutra lutra) in Denmark and Germany. Annales Zoologici Fennici 35: 87–94.Google Scholar
- Raab, B. 1995. Water temperature and ice. In National Atlas of Sweden, Vol. 14. Climate, lakes and rivers, ed. B. Raab, and H. Vedin, 136–141. Stockholm: Swedish Meteorological and Hydrological Institute.Google Scholar
- Räisänen, A., U. Hansson, A. Ullerstig, R. Döscher, L.P. Graham, C. Jones, H.E.M. Meier, P. Samuelsson, and U. Willén. 2003. European climate in the late twenty-first century: regional simulations with two driving global models and two forcing scenarios. Climate Dynamics 22: 13–31.CrossRefGoogle Scholar
- Rask, M., M. Appelberg, T. Hesthagen, J. Tammi, U. Beier, and A. Lappalainen. 2000. Fish survey of Nordic lakes—species composition, distribution, effects of environmental changes. Tema nord 2000, 508, 58 pp.Google Scholar
- Tveito, O.E., E. Førland, R. Heino, I. Hanssen-Bauer, S.H. Alexandersson, B. Dahlström, A. Dreb, C. Kern-Hansen, T. Jónsson, E. Vaarby Laursen, and Y. Westman. 2000. Nordic temperature maps. DNMI—Report 09/00 Klima, 55 pp (in Swedish).Google Scholar