Calf Production, Calf Survival, and Recruitment of Muskoxen on Banks Island during a Period of Changing Population Density from 1986-99

• Published in: ARCTIC
• Main Authors: Larter, Nicholas C., Nagy, John A.
• Format: Article in Journal/Newspaper
• Language: English
• Published: The Arctic Institute of North America 2001
• Subjects: demography; forage; muskoxen; Northwest Territories; Ovibos moschatus; population; weather; démographie; fourrage; boeufs musqués; Territoires du Nord-Ouest; climat; Arctic; Banks Island; Eriophorum scheuchzeri; ovibos moschatus
• Online Access: https://journalhosting.ucalgary.ca/index.php/arctic/article/view/63853

Population estimates for muskoxen (Ovibos moschatus) (age > 1 year) on Banks Island increased from 29 168 (SE 2104) in 1985 to a peak of 64 608 (SE 2009) in 1994 and then declined to 45 833 (SE 1938) in 1998. From 1986 to 1999, annual sex and age classification surveys of muskoxen were conducted during summer. We estimated calf production (number of calves per 100 females aged 2 years or more), calf survival, and recruitment (number of yearlings per 100 females aged 2 years or more). Calf production ranged from 31.3 to 56.3 and was similar between periods of increasing and decreasing density (mean = 42.3 vs. 40.8). Calf survival ranged from 23% to 83% and was generally higher while density was increasing than during its decline (mean = 60 vs. 45). Survival at a given density was lower following the 1994 peak in density. Recruitment ranged from 10.0 to 41.7 and was higher (p = 0.06) during the period of increasing density than during the decline (mean = 28.0 vs. 17.2). Calf survival and recruitment were lowest following two consecutive severe winters, but animal density explained more of the variation in survival and recruitment than did late-winter snow depth. There was a positive relationship between the proportion of sedge (Carex spp., Eriophorum scheuchzeri) in the summer diet and calf survival and recruitment. Patterns of calf survival and recruitment plotted against density were consistent with those modelling a density-dependent relationship. Our results suggest that severe weather alone cannot explain the fluctuations in the population dynamics of Banks Island muskoxen and that underlying density-dependent responses acting upon calf survival and recruitment offer an alternative explanation. Les estimations de population du bœuf musqué (Ovibos moschatus) [âge = 1 an] sur l'île Banks ont augmenté de 29 168 (erreur-type 2104) en 1985 à une valeur crête de 64 608 (erreur-type 2009) en 1994 pour ensuite décliner jusqu'à 45 833 (erreur-type 1938) en 1998. De 1986 à 1999, on a procédé en été à des relevés ...