Chapter 3: Muskox on Devon Island

Ben A. Hubert has studied the "Estimated productivity of muskox on Truelove Lowland". It is in: Truelove Lowland, Devon Island, Canada: a high Arctic ecosystem, L. C. Bliss (ed.) University of Alberta Press, Edmonton, pp. 437-492.

Muskox body weight and growth:

Muskox bull

Seasonal fluctuations in body weight of adult wild muskox in relation to reproductive and environmental conditions.

In May and June 278 kg BW

August 296 kg BW

November, at end of rutting season, 270 kg BW

January 282 kg BW

April 276 kg BW

Muskox cow

1^st of May 223 kg BW

1^st of September 191 kg BW

1^st of February 218 kg BW

Growing season of plants: 1^st of July to 15^th of August = 6 weeks

Snow cover from about 7^th of September to about 30^th of June: 10 months and 1 week

Polar night from about 28^th of October until about the 21^st of February

Polar 24-hour day from about the 25^th of April until the 15^th of August

Calving from about the 15^th of April until about the 7^th of June

Rutting season from 15^th of July until about the 17^th of October.

"If the estimated seasonal weights of adult wild muskox are accurate, seasonal energy balance can be determined. Energy balance in this context will be negative during periods of weight loss and positive during periods of weight gain. It appears, that bulls are in positive energy balance only two months of the year (in summer, July, August), are neutral four months, and negative six months. Cows are positive for five months and negative seven months. ... Adult muskoxen, like most ungulates, continue to grow at a slow annual rate." (1977:480)

Experiments on Muskox Farm at College, Alaska

The results of these experiments showed, that percent digestibility ranged from 64.7 to 63.2% for cows and 64.7 to 62.2% for bulls. There was no significant difference in digestibility between cows and bulls.

Organic matter intake averaged 13.1 g/kg BW in cows and 15.4 g/kg BW day in bulls.

Gross energy intake and digestible energy intake averaged 62.1 kcal/kg BW day and 40.1 kcal/ kg BW day respectively in cows and 73.0 and 46.7 kcal/kg BW day in bulls. About 64% of the organic matter and 66% of the caloric energy was removed from the feed. The coefficient for metabolizable energy is 0.82 (Blaxter 1967). Therefore, 54% of the energy was metabolized.

Metabolizable energy intake (M.E.I.) for the cows was 128.7 kcal/kg^.75 day, and for the bulls 146 kcal/kg^.75 day. Hubert, B. A. (1977:481)

The average weight of the cows, used for the experiment, was 235 kg. The cows gained an average of 0.14 kg day, while the bulls gained 0.15 kg day during the experiments. (1977:482).

Estimated daily intake and output of muskox on Devon Island

*On 9 May, 1972, this bull weighed 264 kg. After B. A. Hubert (1977:482) Table 5.

Estimated daily organic matter and energy intake for muskox on Devon Island

After B. A. Hubert (1977:482) Table 6. I have added here the metabolizable energy (ME) intake. Metabolizable energy (ME) for the muskox on Devon Island is 54% of gross energy (GE). (Hubert, B. A. 1977:481) Table 6.

Energy requirements of wild muskox

"As muskox probably select fresh forage, when it is available, a digestibility of 75% for the snow-free period is possibly an underestimate. Caloric density of organic matter in the forage was 4.78 kcal/gram dry matter, and did not show significant seasonal changes (Muc 1973). Table 6 gives the estimated daily energy intake of the muskox on Devon Island. The summer values are based on June and July data. The winter values are based on the October data and the experimental work from Alaska using captive animals.

"The February D.E.I. value estimated for free ranging muskox was 52.8 kcal/kg BW day, whereas, the same value for pregnant muskox cows in captivity was 40.1 kcal/kg BW day. A 30% greater energy requirement for free-living muskox versus non-active captive muskox seems reasonable. Sheep at pasture expend 21% more energy, than do their penned counterparts (Blaxter 1967). The D.E.I. for the 22-month-old bulls in captivity was 46.7 kcal/kg BW day. Accordingly, the above value for wild muskox is probably an underestimate, especially, when applied to all age groups." Hubert, B. A. (1977:482, 482)

"The areas, most heavily utilized, were meadows of the hummocky sedge type. The available standing crop of graminoid forage in this meadow type, averaged over four seasons, was 62 g m². The other meadow type, utilized, was the frost-boil sedge-moss type, with an available standing crop, averaged over 3 years of 51 g m²." Hubert, B. A. (1977:483).

Adult female muskox, Canadian High Arctic Islands. From: David R. Gray (1987:19) Fig. 1