BACHMAN, G.C.; Univ. of Nebraska, Lincoln: The cost of breeding : Energy availability and the recovery of immune function in recently emerged hibernators.

Injury and subsequent infection are a potential cost of breeding in male mammals. Even where males are not wounded, the immunosuppressive effect of endocrine changes during breeding can increase a male’s susceptibility to disease. Presumably, the costs of immunosuppression are balanced by benefits including a reduction in the energy cost of maintaining the immune system and mounting an immune response. An alternative, but not exclusive, explanation for reduced immune function focuses more directly on the role of limited energy and nutrient resources. A lack of energy or specific nutrients can inhibit the development and maintenance of the immune system, and starvation itself may trigger a stress response independent of other sources of stress during breeding. I investigated the role of energy in the development and maintenance of white cell numbers in Belding’s ground squirrel, a hibernator which has little opportunity to forage prior to breeding in spring. I will describe experiments in which body condition and food availability were manipulated prior to breeding, showing that animals with greater access to resources are able to maintain higher numbers of mature white cells.