Age and tooth wear rate in populations of the reindeer Rangifer tarandus [Russian]

摘要

The wear rate of mandibular premolars and molars was studied in wild reindeer of populations from Taimyr Peninsula (two samplings, 1992 and 1995), the Novaya Zemlya Archipelago, and Wrangel Island. The crown height was measured separately for buccal and lingual wall of each tooth. The age of all reindeer was determined from cementum annual layers in I-1 and M-1. The wear rate of the buccal wall in all teeth and of the lingual wall in M-1 decreased with age in all the populations studied. The wear rate of the lingual wall of the other teeth changed with age differently in different populations. The increase of the wear rate in the oldest animals was revealed in reindeer from Taimyr, in some teeth of reindeer from Wrangel Island, but not in reindeer from the Novaya Zemlya. Relationships between the heights of buccal and lingual walls changed with age differently in different teeth and populations. Results of comparing the wear rates between sampling depended both on the tooth and wall selected and the age composition of samplings. The discriminant analysis of the data obtained from the measurement of walls of five cheek teeth made it possible to distinguish animals of the Taimyr population from those of the population from the Novaya Zemlya. Probably, interpopulation differences in foraging conditions of reindeer affect not only the wear rate but also the configuration of the occlusal tooth surface. The configuration of the occlusal tooth surface influences the relationship between heights of tooth walls in different teeth that was confirmed by the discriminant analysis. According to the equation of linear regression of the crown height, one can determine an approximate age of some individuals of the population, for which the equation was constructed. It could not be used for individuals of other populations of the same species. The power equation that describes the relations between the crown height and age proposed and tested on Bovidae by Spinage (1971) turns out to be more suitable for an approximate assessment of the age of reindeer if it is constructed on the basis of factual data. The determination of age in individual reindeer of the middle-aged group by this equation gives better results than that using the equation of linear regression. Constant k that is calculated for one reindeer population appears to be valid for another one.