Body Condition and Adjustments to Reproductive Effort in Female Moose (Alces alces)

We studied condition and reproduction of moose (Alces alces) in southcentral Alaska using ultrasonography to determine rump-fat thickness and numbers of corpora lutea and embryos in early gestation, and intensive radio-tracking of the same animals in spring to measure rates of calving and neonatal survival. Rump-fat thickness, pregnancy rate, and embryo size were less among female moose accompanied by a calf in autumn. Fifteen percent of ovulations failed to result in a detectable embryo, and additional reproductive losses occurred between early gestation and birth. Body condition in the autumn was correlated positively with pregnancy and calving rates and negatively with reproductive losses in both early and late gestation and neonatal mortality. Our study documents the extent to which body condition and prior reproductive success affect adjustments to reproductive effort made by female moose within a single reproductive cycle.