SOCIAL-STATUS AND PHYSICAL CONDITION OF MOTHER AND SEX-RATIO OF OFFSPRING IN CERVIDS

In cervids, the degree of polygyny and litter size vary between specie s, and both these variables can potentially influence the relationship between maternal condition and offspring sex ratio. Good foraging con ditions have usually been found to favour a trend toward female-biased population birth sex ratios. This appears to apply to even the most p olygynous species, red deer (Cervus elaphus) and reindeer (Rangifer ta randus). However, analysis of offspring sex ratio within populations o f these species indicates that high-ranking females produce more males than low-ranking ones. Owing to monoparity and a high degree of polyg yny, these species probably offer the dearest starting points for eval uating Trivers and Willard's hypothesis that, in the case of polygynou s mammals, females in good condition produce more males than females i n poorer condition. In the genera Odocoileus and Alces litter size is not fixed to one, and parental investment per litter may therefore be affected by both offspring sex and litter size. Available evidence of offspring sex ratio variation within these genera is less conclusive t han in Cervus and Rangifer. (C) 1997 Elsevier Science B.V.