Behavioral Ecology and Sociobiology

, Volume 56, Issue 6, pp 546–551 | Cite as

Effects of body mass, age, dominance and parasite load on foraging time of bighorn rams, Ovis canadensis

  • Fanie PelletierEmail author
  • Marco Festa-Bianchet
Original Article


In sexually dimorphic ungulates, males generally spend less time foraging than females, possibly because of difference in body mass or because of the energetic requirements of lactation. The relationship between body size and foraging time has received little attention at the intra-specific level, because few studies have documented activity budgets for individuals of known size. Bighorn rams are a good model to explore how body mass affects foraging time, because they range in mass from 55 to 140 kg. We examined how the foraging time of bighorn rams varied according to individual characteristics. We observed rams in a marked population and constructed time budgets during the 3 months preceding the rut. We determined ram social rank based on agonistic encounters and collected fecal samples to count lungworm larvae. Time spent foraging was negatively correlated with body mass. After accounting for age differences, larger rams spent less time foraging and more time lying than smaller rams. Among rams aged 6–12 years, dominants spent less time feeding than subordinates, while fecal output of lungworm larvae was negatively correlated with foraging time for rams of all ages. Body mass accounts for much of the individual variation in foraging time, suggesting that sexual dimorphism is important in explaining differences in feeding time between males and females.


Bighorn sheep Body mass Foraging Ovis canadensis Time budget 



We thank Y. Gendreau, É. Viollet, K.A. Page and C. Feder for help in the field. We are grateful to A. von Hardenberg for assistance with statistics. For critical comments on the manuscript, we thank Kathreen Ruckstuhl, Norman Owen-Smith and Jean-Michel Gaillard. We also thank Jack Hogg for his continuous help and advice. We dedicate this paper to the late Ian Ross, who made a major contribution to this long-term study by capturing and tagging bighorns from 1989 to 2002. Financial support was provided by a Challenge Grant in Biodiversity financed trough the Alberta Conservation Association and the University of Alberta (to F.P.), NSERC Discovery grant to M.F.-B. and a NSERC scholarship to F.P. We thank the Kananaskis Field Stations (University of Calgary) for logistic support. This research project (protocol MFB 02) was approved by the Animal Care Committee of the Université de Sherbrooke, an affiliate of the Canadian Council on Animal Care.


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Copyright information

© Springer-Verlag 2004

Authors and Affiliations

  1. 1.Département de biologieUniversité de SherbrookeSherbrookeCanada

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