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Body-condition dynamics in a northern ungulate gaining fat in winter

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Abstract:

Individual condition generally depends on density and is partly determined by habitat quality and climate. We studied long-term trends in the condition and productivity of female caribou (Rangifer tarandus (L., 1758)) in two large migratory herds in the Quebec-Labrador peninsula (Canada), the George and the Feuilles herds. Females from the George herd were in better summer condition than those from the more abundant Feuilles herd in 2001-2002, while it was the opposite in 1988 when the Feuilles herd was less abundant than the George herd. Summer nutrition followed the same pattern between herds through time. Spring body condition of females in the George herd declined from 1976 to the mid-1980s during early population growth. Fall condition, however, did not change from 1983 to 2002 when caribou numbers first peaked and later declined. Pregnancy rates were inversely related to herd size in both herds. Vegetation quality (NDVI) in June was significantly related to body proteins in the fall. Albeit unusual for a northern ungulate, body fat increased from fall to spring in the George herd. We conclude that a relatively small and highly grazed summer range, as well as density-dependent effects, affected summer nutrition and the need to continue lipogenesis during winter.

La condition physique des animaux dépend généralement de la densité de la population et est partiellement déterminée par la qualité de l’habitat et le climat. Nous avons étudié les variations à long terme de la condition corporelle et de la productivité des femelles du caribou (Rangifer tarandus (L., 1758)) dans deux grands troupeaux migrateurs de la péninsule du Québec-Labrador, les troupeaux George et Feuilles. Les femelles du troupeau George étaient en meilleure condition estivale que celles du plus grand troupeau Feuilles en 2001-2002, tandis que le contraire s’observait en 1988 alors que le troupeau Feuilles était moins abondant que le troupeau George. La nutrition estivale a suivi le même patron temporel chez les deux troupeaux. La condition printanière des femelles du troupeau George s’est détériorée de 1976 jusqu’au milieu des années 1980 durant la phase initiale de croissance démographique du troupeau. La condition automnale, toutefois, n’a pas varié entre 1983 et 2002 alors que les effectifs atteignaient d’abord un sommet, puis déclinaient. Le taux de gestation était inversement relié aux effectifs chez les deux troupeaux. L’abondance de la végétation (NDVI) en juin était significativement reliée aux protéines corporelles en automne. Quoique cela semble inhabituel pour un ongulé nordique, le gras corporel a augmenté entre l’automne et le printemps dans le troupeau George. Nous concluons qu’une aire estivale relativement petite et surpâturée ainsi que des effets dépendants de la densité affectent la nutrition estivale et le besoin de poursuivre la lipogénèse en hiver.

Document Type: Research Article

Publication date: 2009-05-01

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  • Published since 1929, this monthly journal reports on primary research contributed by respected international scientists in the broad field of zoology, including behaviour, biochemistry and physiology, developmental biology, ecology, genetics, morphology and ultrastructure, parasitology and pathology, and systematics and evolution. It also invites experts to submit review articles on topics of current interest.
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