The oral anatomy of Arctic ruminants: coping with seasonal changes

We studied the feeding apparatus of three species of northern ruminants rep resentative of three feeding types: muskoxen Ovibos moschatus, Norwegian re indeer Rangifer tarandus tarandus and high Arctic Svalbard reindeer Rangife r tarandus platyhrynchus and Siberian musk deer Moschus moschiferus. The sh ape of the muzzle, the incisor arcade, the incisiform and the molariform te eth indicate that these species are selective feeders, irrespective of thei r body size or their position on the grazer-concentrate selector continuum of feeding types. Narrow muzzles seem well adapted for selective feeding on the diminutive but highly nutritious plants, or parts of plants, on tundra swards and Arctic-alpine meadows and enable the animals to maximize nutrie nt intake during the short summer. However, their small mouths presumably a lso restrict reindeer and muskoxen to taking small bites, thereby achieving low rates of dry matter intake when feeding on the very short swards in wi nter. This is partially obviated by two general strategies; a reduction of energy requirements in winter and, in Norwegian reindeer, migration inland to where foraging conditions are generally more favourable. In Svalbard rei ndeer, which have little access to lichens or other easy digestible plants in winter, rumen fill increases through the accumulation of slowly fermenti ng fibrous foods. Despite their narrow muzzles, reindeer and muskoxen are u nable to avoid ingesting a certain amount of poor quality forage in winter and cope with this by appropriate modification of digestive function.