Female Soay sheep do not adjust their maternal care behavior to the quality of their home range: Does home range quality influence maternal care?

Resource availability, through its impact on the costs and benefits of parental care, is expected to influence parental care behavior. There has, to our knowledge, been no attempt to understand how variation in the resource use of wild individuals influences individual parental care behavior. To understand how natural resource variability affects maternal care in female St. Kilda Soay sheep, we selected 69 females whose home ranges varied in quality (measured as the mean percentage cover of Holcus lanatus), and recorded the behavior of each individual and her lamb over the period of maternal care. Home range quality did not influence suckling or non-suckling behaviors of the female or her lamb, suggesting that maternal care did not vary with a female's access to resources. Growth rate analyses confirmed the behavioral results, with no association between home range quality and the weight gain of lambs between birth and weaning. This work suggests that female Soay sheep faced with poorer resources do not favor their own future success over that of their lamb, and thereby do not exhibit a conservative reproductive strategy. This may be because when resource levels are high during the summer, females are able to offset the costs of lactation by consuming additional resources, regardless of the location of their home range. Our results suggest that more studies characterizing the environment experienced by individual animals will be necessary to fully understand how individuals alter their behavior in response to temporal and spatial variation in the environment.