Behavioral Ecology and Sociobiology

, Volume 64, Issue 6, pp 939–946 | Cite as

Sexual dimorphism and the mating ecology of polar bears (Ursus maritimus) at Svalbard

  • Andrew E. Derocher
  • Magnus Andersen
  • Øystein Wiig
  • Jon Aars
Original Paper

Abstract

We assessed the role of size, mass, and age in mating and non-mating polar bears (Ursus maritimus) at Svalbard, Norway, during the spring breeding season. The ratio of male to female mass, in male-female pairs, ranged from 1.00 to 3.02 (\( \overline x = 1.99 \)) indicating that mating males were larger than mating females but with substantial variation. Paired males were older than unpaired males and male mass was related to age. However, males paired with females were not significantly different in body mass from those males caught alone. Wounds and scars resulting from fights between males began at about 6 years of age and peaked at about 17 and 20 years of age, respectively. The frequency of broken canines in males, presumably due to increased male-male conflicts, increased with age but showed little increase in females. The wide range of male size in male-female pairs and the age-related signs of injury suggest that male polar bears engage in both scramble competition and contest competition for access to breeding females. The mating system of polar bears is variable but is best described as female defense polygyny or serial monogamy.

Keywords

Mating system Polar bears (Ursus maritimusFemale defense polygyny Serial monogamy Sexual dimorphism 

Notes

Acknowledgments

Assistance in logistics was kindly provided by the Governor of Svalbard. We are grateful for the help of the Hopen Radio staff who provided an excellent base for operations. The Norwegian Polar Institute funded this study with assistance from the Norwegian Research Council and the World Wildlife Fund. Ages of bears were determined by D. Andriashek and C. Spencer of the Canadian Wildlife Service, Environment Canada, Edmonton. Animal handling methods were approved by the National Animal Research Authority (P.O. Box 8147 Dep., N-0033 Oslo, Norway) and complied with Norwegian law. S. Amstrup kindly provided helpful comments on an earlier draft of this paper.

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Copyright information

© Springer-Verlag 2010

Authors and Affiliations

  • Andrew E. Derocher
    • 1
  • Magnus Andersen
    • 2
  • Øystein Wiig
    • 3
  • Jon Aars
    • 2
  1. 1.Department of Biological SciencesUniversity of AlbertaEdmontonCanada
  2. 2.Norwegian Polar InstituteTromsøNorway
  3. 3.National Centre for Biosystematics, Natural History MuseumUniversity of OsloBlindernNorway

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