Influence of social factors on immune function and reproduction

Animals are presented with continuous energy demands that vary seasonally. For example, during the winter many small mammals and birds inhibit reprodu ction and growth and funnel energy into thermogenesis or cellular maintenan ce. As energy shortages become more severe, survival may become compromised because processes such as immune function and thermogenesis are impaired. Thus, there are trade-offs between energetically expensive processes such a s reproduction and immune function. In this review, the immune function and reproduction of seasonally breeding species are evaluated in relation to s ocial interactions. It is proposed that individuals maintain the highest de gree of immune function that is energetically possible within the constrain ts of other survival needs, as well as growth and reproduction, in habitats in which energy requirements and availability often fluctuate. It is hypot hesized that extrinsic factors, such as social environment, modulate energy allocation to reproductive and immune function and that hormonal mechanism s underlie the partitioning of energy to various physiological components.