Reproduction is energetically expensive for mammalian females and seasonality limits the amount of time available to successfully reproduce. Temperate mammals often have methods to cope with time constraints, such as thermoregulatory and foraging flexibility, but typically at a cost. However, foraging and thermoregulation are often studied separately, which leads to limited knowledge about what, if any, relationship exists between these two factors. The purpose of my research was to determine how thermoregulation and foraging patterns vary among reproductive stages in big brown bats (Eptesicus fuscus) that switched between building and tree roosts. I equipped pregnant and lactating bats with temperature sensitive radio-transmitters in southwest Saskatchewan, Canada. While transmitters were active, skin temperature data were collected using a datalogger and foraging patterns determined by triangulation. Thermoregulatory patterns remained similar between reproductive conditions, but with slightly more heterothermy employed during lactation, especially when roosting in trees. Lactating bats had a tendency to forage for longer duration than pregnant bats, and often took more foraging trips as well. When coupled together, I found that foraging duration and torpor duration were not directly related during pregnancy, but exhibited a slightly inverse relationship during lactation. These data provide support for the hypothesis that the relationship between thermoregulation and foraging is not constant throughout reproduction, which may be due to the trade-off between slowed development of young through torpor use and risky foraging for the female during suboptimal conditions.