DOES FOOD AVAILABILITY AFFECT GROWTH AND SURVIVAL OF MALES AND FEMALES DIFFERENTLY IN A PROMISCUOUS SMALL MAMMAL, TAMIASCIURUS-HUDSONICUS

1. In dimorphic mammals, males grow faster than females, but often suffer higher mortality during periods of resource shortage. 2. We compared growth and survival of males and females in a promiscuous small mammal with a relatively small degree of dimorphism (male/female body mass ratios ranged from 1.05 to 1.11). 3. We compared two geographically distinct populations over 4 years during which natural food levels varied considerably. We also experimentally supplemented and reduced food levels. 4. Birth weights and preweaning growth rates did not differ between sexes, but growth rates differed between years. 5. Survival to weaning was lower in males than in females in one year and one population only. This followed a winter of complete failure of the cone crop, the primary food source. 6. Post-weaning growth rates of males and females differed in some years but regardless of the degree of difference, post-weaning survival rates of the two sexes were equal. 7. Experimental addition and reduction of food did not affect growth or survival of the two sexes differently. 8. We conclude that changing resource levels do not affect growth and survival of male and female red squirrels differently.