A Comparison of First-Year Growth in Wild and Captive Muskox Calves

Posted on May 2, 2018

Author

by Jan ADAMCZEWSKI, Peter FLOOD, Anne GUNN, Bernard LAARVELD, and Susan TEDESCO
CWBM 7 (1): 67–89

Correspondence: J. Adamczewski, GNWT ENR, Box 1320, Yellowknife, Northwest Territories, X1A 2L9, Canada. 

Email: jan_adamczewski@gov.nt.ca


Abstract

We measured seasonal changes in body composition, including fatness and fill in the digestive tract, in 79 muskox (Ovibos moschatus) calves shot by Inuit hunters in April, May, July, August, September and November, 1989-1993, on Victoria Island in northern Canada. We compared their growth to that of 3 calves born in captivity near Saskatoon and 4 calves live-caught at about 2 weeks of age, then raised in captivity in 1993-1994. Muskox calves on Victoria Island grew from 15.9 ± 0.9 kg (mean ± standard error) body mass in mid-late May, when they were about 2 weeks old, to peak fall mass in November of 82.9 ± 2.3 kg. These calves had an estimated 16.5 ± 1.1 kg fat in November but lost 80% of this fat by April. Muskox calves ingested plant material and detritus from their first day on and by summer the fill in calf digestive tract chambers was proportionately very similar to that of adults. The growth of 7 captive calves in Saskatoon initially was similar to that of the wild calves, but these calves were weaned at the end of July, and thereafter their growth was slower than in the wild. Over winter, however, the captive calves continued to grow slowly, while the wild calves lost mass and their linear growth nearly ceased. Serum insulin-like growth factor 1 (IGF-1), a hormone known to correlate closely with growth rate, was initially similar in the wild and captive calves, but dropped rapidly in the captive calves when they were weaned. Muskox calves benefit from a prolonged first growth season to become full ruminants in early summer, and they build substantial fat and protein reserves when entering their first winter.

Key Words: Body Composition, Calves, Fatness, Growth, Muskox, Nunavut.

7-Adamczewski-et-al-7-1

 

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