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Effects of age, density and sex ratio on reproductive effort in male reindeer (Rangifer tarandus)

Published online by Cambridge University Press:  25 November 2003

Atle Mysterud
Affiliation:
Department of Biology, Division of Zoology, University of Oslo, P.O. Box 1050 Blindern, N-0316 Oslo, Norway
Øystein Holand
Affiliation:
Department of Animal Science, Agricultural University of Norway, P.O. Box 5025, N-1432 Ås, Norway
Knut H. Røed
Affiliation:
Department of Morphology, Genetics and Aquatic Biology, The Norwegian School of Veterinary Science, P.O. Box 8146, Department N-0033 Oslo, Norway
Hallvard Gjøstein
Affiliation:
Department of Animal Science, Agricultural University of Norway, P.O. Box 5025, N-1432 Ås, Norway
Jouko Kumpula
Affiliation:
Finnish Game and Fisheries Research Institute, Reindeer Research Station, Fin-99910 Kaamanen, Finland
Mauri Nieminen
Affiliation:
Finnish Game and Fisheries Research Institute, Reindeer Research Station, Fin-99910 Kaamanen, Finland
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Abstract

In sexually dimorphic ungulates, male reproductive success depends on fighting with other males for access to females during a brief rutting season. Large body size is necessary for success in intrasexual competition, and a few large-sized males are often able to monopolize access to female groups. Earlier studies have reported that reproductive effort increases with age until prime-age is reached, and one study that population density lowered effort in (older) males. No study has directly assessed whether there is within-age-class variation in effort resulting from varying levels of intra-male competition. It is reported here the weight loss during the rutting season of 54 individual male reindeer Rangifer tarandus coming from eight herds with varying density (3.3–6.0 deer/km2) and sex ratio (4–28% males). In agreement with earlier studies, reproductive effort was lower for young (1- to 2-year-old) than for prime-aged (3- to 5-year-old) males both on an absolute and relative scale. Among 1-year-old males (n=33), effort was lower as sex ratio became closer to even, but density during the rutting season had no effect. This suggests that yearling males take a more active role when prime-aged males are absent. In addition to the insight into male ungulate life history, understanding male rutting behaviour may also have implications for population dynamics.

Type
Research Article
Copyright
2003 The Zoological Society of London

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