The high, constant body temperatures (T_b) of endotherms like birds and mammals are thought to facilitate the specialization of biochemical processes to warm temperatures, but endotherms experience temperature variation in body regions that can be extreme, even as they tightly regulate core T_b. Bats have poorly thermally insulated wing muscles, separated from the environment by only a thin layer of skin and little to no fat or fur, making them vulnerable to heat loss. We hypothesized that (1) peripheral muscles further from the core would operate at lower temperatures than core muscles; (2) to compensate for lower operating temperatures, these peripheral muscles would be less temperature sensitive than core muscles; and (3) differences in the temperature sensitivity of muscle contractile properties would be due to differing properties of the enzymes that mediate muscle contraction. We addressed these hypotheses in Carollia perspicillata, a Neotropical fruit bat, by measuring wing muscle temperatures continuously during wind tunnel flights; shortening velocity and relaxation rates across temperatures in strips of the pectoralis and whole muscle preparations of a forearm and hand muscle from the same species; and myosin enzyme activities from the pectoralis and forearm muscles across temperatures. In vivo pectoralis temperatures matched T_b closely, but forearm muscle temperatures were 12ºC below T_b on average. Contractile rates in the peripheral muscles were significantly less temperature sensitive than those of pectoralis, suggesting that they are able to better maintain function at their low operating temperatures, which is likely due to a significant difference in thermal stability of myofibrillar ATPase between the pectoralis and forearm muscles.