Fathers, fat, and maternal energetics in a biparental hamster: Paternal presence determines the outcome of a current reproductive effort and adipose tissue limits subsequent reproductive effort

Djungarian hamster females, Phodopus campbelli, are severely constrained in their ability to reproduce successfully and lose 20% of their body weight by the time pups are weaned. In the wild and in the laboratory, biparental care improves maternal reproductive success. Two experiments quantified the effects of paternal presence and partial lipectomy [surgical depletion of parametrial white adipose tissue (PWAT) on day 8 of the 18-day gestation] o n maternal energy balance, reproductive success, and investment in a subseq uent reproductive attempt. Paired females reproduced successfully, maintain ed body weight, and invested in a second litter. Removal of the male decrea sed pup survival, growth, and readiness for dispersal by 18 days of age. So litary females lost 10% of their body weight by the birth and a further 10% by day 18 after the birth. Thus, paternal presence balanced maternal energ y budgets during reproduction and prevented a 20% loss in body weight. Equi valent weight loss occurs in response to other maternal stressors, therefor e 20% may be the maximum tolerable weight loss in this species. Fresh weigh t of interscapular brown adipose tissue was predicted by the extent of mate rnal hyperthermia but not by maternal energy balance or lipectomy. Partial lipectomy did not adversely affect the female or the first litter but decre ased the probability of investment in a second reproductive attempt and hal ved the size of the second litter. This effect may have been due to the 0.1 % of body weight amount of lipid removed or may reflect a specialized role for PWAT in adjusting maternal investment. (C) 2000 Academic Press.