Factors affecting maternal care in an income breeder, the European roe deer

1. Maternal care is a major component of demographic tactics in mammals. In ungulates most work has been done on capital breeders (e.g. bighorn sheep) , which rely heavily on body reserves to raise their young. Roe deer, in co ntrast, are close to the income breeder end of the capital-income breeder c ontinuum, and show high levels of maternal care. 2. The aim of this study was to explore the factors determining the level o f maternal care in roe deer, in particular the effects of maternal body wei ght, mother's parity, litter size and year of birth on the amount of prenat al care (i.e. the average mass of an offspring multiplied by the number of offspring) and postnatal care (i.e. the average growth rate of the offsprin g multiplied by their number). The study was carried out on a captive popul ation of roe deer fed ad libitum, and in a wild population. 3. In both populations prenatal care increased with increasing maternal bod y weight. In the population fed ad libitum this effect was found in light f emales only (< 22 kg); in the wild population the positive relationship bet ween maternal body weight and prenatal care was entirely accounted for by v ariation in litter size (i.e. heaviest females produced larger litters) and density (i.e. females were lightest in years with high population density) . Parity did not affect prenatal care. 4. In 14 females fed ad libitum there was no relationship between postnatal care and maternal body weight. Multiparous females had higher levels of po stnatal care. In contrast, 20 wild females showed a positive relationship b etween postnatal care and maternal body weight, and only litter size affect ed the level of postnatal care. 5. Even after accounting for the confounding effects of maternal body weigh t, parity, litter size and population density, we found no trade-off betwee n pre- and postnatal care in any of the two populations. The conditions und er which the pattern of maternal care could impose trade-offs that affect t he individual offspring are discussed.