Abstract
It has been suggested that muskoxen calve earlier with increasing latitude but the available data do not seem to have been thoroughly analyzed. Therefore, estimated conception dates (K=657) from a wide range of latitudes were compared. The results indicate that conceptions occur about a month earlier in the arctic than at temperate latitudes. This conclusion is consistent with reported observations of mating behaviour and calving season.
Highlights
In many small mammals breeding begins later with increasing latitude and its timing is closely related to plant phenology and food supply (Sadlier, 1969; Bronson, 1985)
Mating may have been artificially delayed in the confined herds at Unalakleet, Fairbanks and Palmer by keeping the males and females separate until a predetermined date early in the breeding season
The controlled mating system used in Palmer, Fairbanks and Unalakleet probably had little effect on the conception dates that were included in the analysis owing to the use of the truncation procedure. Further evidence for this view comes from the dates of unconstrained conceptions at Anchorage and Lycksele (Fig. 1) and the fact that none of the estimated dates of conception were less than eight days after the bulls were introduced when introduction occurred early in the season
Summary
In many small mammals breeding begins later with increasing latitude and its timing is closely related to plant phenology and food supply (Sadlier, 1969; Bronson, 1985). Breeding species differ in their characteristic time of birth and muskoxen, for example, calve about 4 - 8 weeks before sympatric caribou (Latour, 1987; Leader-Williams, 1988). In all cases other than Banks and Victoria Islands a gestation period of 235 days (Rowell et al, 1993) was deducted from the known calving date.
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