Seasonal and Sexual Patterns of Growth and Condition of Reindeer Introduced into South Georgia

Abstract

The pattern of growth, timing and magnitude of seasonal changes in body weight and condition were compared between male and female reindeer. The data were derived from 300 animals shot during an eighteen month period on the sub-Antarctic island of South Georgia. Growth in length and weight from early foetal life until one year of age was logistic. A sex difference in skeletal size became apparent only after one year of age although by then males were already significantly heavier than females. Organ and gastrointestinal weights changed first in the annual cycle and these changes were related to annual changes in forage quality and availability. In contrast, changes in body and leg weights and in fat reserves were related to reproductive activity: in males they declined after the rut whereas in females they reached a minimum around parturition. Although both sexes probably metabolized muscle protein as well as fat during the winter, male reindeer lost twice as much of their body tissue during the annual cycle as females. These results indicate that the cost of reproduction is greater to males than to females and this reflects their different reproductive strategies