Meeting Abstract
Physiological processes used to obtain, extract, transform, and allocate resources from the environment (i.e., activity, digestion, metabolism, lactogenesis) create heat that is either used to maintain a high body temperature or must be dissipated to the environment to maintain homeostasis. The ‘heat dissipation limitation’ hypothesis suggests that the ability to dissipate endogenous heat affects the capacity of endotherms to manipulate and allocate resources from their environment to their offspring. Female American red squirrels (Tamiasciurus hudsonicus) that delay reproduction (due to decreases in food abundance) are under selection to reduce investment in their offspring (realized as lower growth rates of offspring). Delays in reproduction by red squirrels coincide with the warmest parts of summer, which may exacerbate heat dissipation constraints and the ability to allocate resources to offspring. Hypothesis: reproductive output of female red squirrels is limited by their capacity to dissipate heat and by the lack of resources available in their environment. We predict that females that have their capacity to dissipate heat increased, will be able to transform resources to a fuller extent and increase investment in their offspring. We reduced the insulation of free-living red squirrels (by reducing dorsal fur cover using an electric razor) and followed them throughout reproduction to quantify metrics of reproductive output (i.e., litter mass and size, growth rates of individual offspring). This study is the first to combine a manipulation of the capacity to dissipate heat and to quantify reproductive output of a mammal in the wild.
