Offspring sex ratio of red deer before and after an intensive drought in Patagonia

FLUCK, WT

Bariloche, Argentina

Congreso; Reunión Argentina y Chile de Ecología; 2001

Red deer (Cervus elaphus) have reached high densities in areas of Patagonia. Drought conditions during 1998/99 were suspected of impacting reproduction. Females were at borderline of body condition allowing conception; necropsies of 50 adult females during winter 1999 revealed pregnancy rates lowered by 44%. The fetal sex ratio (71% males) deviated significantly from unity: 90% of primiparous females had males, the following age class had all females, the middle age class had all males, and older females had equally male or female fetuses. The fetal sex ratio was 46% males (n=69) measured during the preceding 7 years. The male-biased fetal sex ratio in 1999 contrasts certain other reports that only females in best condition tended to have male-biased offspring. However, such ambivalent results may stem from not having evaluated body fat reserves and reproductive tracts, or studies conducted during environmental conditions not extreme enough. These results indicate that red deer populations occur at densities where they can easily become food-limited through a singular environmental phenomenon such as a drought. Although recruitment rates were drastically reduced through the drought, red deer can recuperate rapidly and thus would continue to exert intensive pressure on flora if population densities are not lowered through hunting.