Evidence for a trade-off between growth and body reserves in northern white-tailed deer

We contrasted patterns of growth and accumulation of body reserves in autum n between two high-density (HD) white-tailed deer populations facing winter s of different severity and length. Both populations occurred in the absenc e of effective predators and suffered from some forage competition based on reduced body masses. A third population living at low density (LD) and con fronting long and severe winters (SW) served to distinguish the influence o f food competition and winter severity on growth and body reserves. We esti mated body components (water, protein, fat and ash) of deer during the firs t half of November and compared growth patterns between sexes and regions. HD-SW males continuted growth to an older age than KD males facing short an d mild winters (MW) but females of both regions reached adult body mass at the same age. LD-SW deer exhibited a growth pattern similar to that of HD-S W animals but were the heaviest and the largest, suggesting that growth pat terns are related to winter harshness (or length of the growing season) and that final body size is related to forage competition in summer. Sexual di morphism became evident at an older age in the HD-SW population than in the HD-MW population, demonstrating that winter harshness does not affect imma ture males and females in the same manner. Fawns from the KD-SW population had proportionally longer legs and a higher percentage of body fat. Adaptat ions of immature deer to long and severe winters suggest that survival duri ng the first winter represents the most critical step in the life span of n orthern while-tailed deer.