Maternal time budgets of feral goats at high latitudes in northwest Europe.

Reproduction is energetically expensive for mammals, and especially so during lactation. In large-brained mammals such a primates, females invest heavily in additional feeding to fuel the costs of lactation. The evidence is more mixed in ruminant ungulates. We examine the foraging costs of lactating female feral goats living under environmentally challenging conditions in the northwest of Scotland where these effects are most likely to be exaggerated. We show, using data from three separate studies, that, compared to matched non-lactating females, lactating females do increase the time devoted to foraging, but only to a limited extent that is well below the theoretical requirements of their kids. Although they do not alter their diet, lactating females spend more time in shelter and at lower altitudes in order to reduce thermoregulatory costs. At high latitudes, the rate at which kids grow is such that females cannot afford to extend lactation much beyond two months. This will inevitably set a limit on ungulates capacity to produce large-brained offspring. HighlightsO_LILactation is costly, obliging females to increase food intake or draw on body fat C_LIO_LIAt high latitudes, goats increase foraging, but not enough to meet kids demands C_LIO_LIFemales do not forage on richer foods, but they do try to minimise thermal costs C_LIO_LIAs a result, females have high mortality after weaning when forage quality is poor C_LI