Carrying of Young by Flying Female North American Bats

Occasional transportation of young by flying female bats is a well established phenomenon. Transportation of young within a roost, or even from roost to roost, may be a normal occurrence in certain species and may provide certain survival advantages. However, it is apparent that most examples reported in the literature have resulted from disturbances, and consequently these cannot be considered as representing normal (= undisturbed) behavior. In many species, the transportation of young by flying females may be at all times an uncommon and atypical activity. In any case (and contrary to popular opinion), evidence presently available is insufficient to prove that of young while foraging occurs in any North American species, and such behavior is thought not to take place in several. The author strongly suspects that this is not done by any insectivorous bats. Assuming that female bats possess typical mammalian behavioral traits involving care of altricial young, and noting the lack of any type of nesting behavior, it would seem logical to assume that adult females would routinely carry their young about with them during flight. Verification of such behavior is apparently provided by many published accounts (Table 1). However, further analysis reveals that these reports verify only that certain female bats of several species have been observed on certain occasions to fly (with various degrees of success) while carrying young attached to their nipples. These observations do not provide any evidence as to the extent and function of this behavior and, consequently, several questions remain unanswered. Table 1 includes references to 14 species representing four families. While the construction of this table was in no way an attempt to compile all references to the carrying of young, these data are of sufficient breadth to strongly suggest that such an ability is relatively common throughout the Chiroptera. When one considers the rather uniform nature of the gross morphology of bats in general, especially in terms of the arrangement of the flight surfaces, it would not be unreasonable to suppose that the ability to carry newborn young in flight is a universal bat characteristic. But the evidence for such an assumption is far from conclusive. There is no real justification, for example, for Brehm's statement (1895: 79), All bats carry their young ones around with them when they fly. . ., especially since this implies that such behavior is a common and normal part of the way of life of all bats. Although the data in Table 1 provide evidence that bats of several species can carry their young, very few of the observations indicate that this behavior occurs in the absence of disturbance. Young bats, with the aid of their recurved milk teeth, cling tenaciously to the nipples. I have found that young Antrozous pallidus can