Diet choice exaggerates food hoarding, intake and pup survival across reproduction.

Siberian hamsters increase food intake and hoarding during pregnancy and lactation, perhaps to compensate for large decreases in body fat (approximately 50%). We tested the effects of diet choice on these responses in pregnant, lactating and virgin hamsters housed in a simulated burrow system. Hamsters were offered pellet chow (PC) or a choice of sunflower seeds (SS), rabbit chow (RC) and PC. Pregnant or lactating PC-fed hamsters had increased food intake and hoard size compared with virgins, effects exaggerated by diet self-selection. The pregnancy-induced increases and lactation-induced decreases in body mass were enhanced and diminished by diet self-selection, respectively. Pregnant self-selecting hamsters ate relatively more carbohydrate and less fat and hoarded less carbohydrate and more fat than their virgin counterparts (protein not affected). Lactating and virgin self-selecting hamsters both ate and hoarded relatively more carbohydrate than protein or fat compared with PC-fed hamsters but were not different from each other. Litter and pup sizes were similar at birth, but pups from self-selecting mothers had decreased lipid content (50%) compared with pups from PC-fed mothers, whereas at weaning they were heavier but not fatter. Only lactating PC-fed mothers cannibalized their pups (approximately 60% eaten, 8/10 litters). The pregnancy-induced increased eating and hoarding of carbohydrate may have helped meet immediate energy needs sparing dwindling lipid reserves, whereas the decreased fetal lipid investment may have helped conserve energy in anticipation of the increased demands of lactation. The diet-induced exaggerated caloric intake and food hoard size of lactating hamsters may have promoted pup growth and survival.