The body temperature varies, depending on the ambient temperature. When the body temperature is cooler the bats enter a state of torpor and remain in that state until the body temperature has warmed. In order to cool body temperature, they show behavioral thermoregulation by spreading out in the roost into smaller groups. Myotis nigricans is primarily insectivorous with few cases of observed fruit consumption. Young bats have high mortality rates because of predation, disease, and parasitism. Opossums, cats, and other bats are some mammalian predators of the black myotis. Other predators include snakes, cockroaches, and spiders. Young bats also face the trouble of ectoparasites, including mites, bat mites, soft ticks, hard ticks, chigger mites, fleas, and bat flies.