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Several polygynous mammals exhibit reproductive skew in which only a few males reproduce. Successful males need strength, stamina and fighting ability to exclude competitors. Consequently, during the mating season their androgens and glucocorticoids are expected to increase to support spermatogenesis and aggressive behavior. But, during the nonmating season these hormones should decline to minimize deleterious effects, such as reduced immune function. Bats that exhibit harem polygyny in which males aggressively defend large groups of females year-round are ideal for assessing hormonal and other consequences of extreme polygyny. Here we use DNA methylation to estimate age and gas chromatography, tandem mass spectrometry to profile steroid metabolites in urine of wild greater spear-nosed bats, Phyllostomus hastatus, across seasons. We find that condition, measured by relative weight, is lower during the mating season for both sexes, although it remains high in harem males during the mating season. Average age of females is greater than males, and females exhibit substantial seasonal differences in androgens, estrogens and glucocorticoids with higher levels of all hormones during the mating season. Males, however, show little seasonal differences but substantial age-associated increases in most steroid metabolites. Harem males have larger, persistently scrotal testes and are older than bachelor males. While cortisone generally declines with age, harem males maintain higher amounts of biologically active cortisol than bachelor males all year and cortisol levels increase more quickly in response to restraint in males than in females. Taken together, these results suggest that attaining reproductive dominance requires hormone levels that reduce lifespan., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Intranasal oxytocin (OT) delivery has been used to non-invasively manipulate mammalian cooperative behavior. Such manipulations can potentially provide insight into both shared and species-specific mechanisms underlying cooperation. Vampire bats are remarkable for their high rates of allogrooming and the presence of regurgitated food sharing among adults. We administered intranasal OT to highly familiar captive vampire bats of varying relatedness to test for an effect on allogrooming and food sharing. We found that intranasal OT did not have a detectable effect on food-sharing occurrence, but it did increase the size of regurgitated food donations when controlling for dyad and amount of allogrooming. Intranasal OT in females increased the amount of allogrooming per partner and across all partners per trial, but not the number of partners. We also found that the peak effect of OT treatments occurred 30-50min after administration, which is consistent with the reported latency for intranasal OT to affect relevant brain areas in rats and mice. Our results suggest that intranasal OT is a potential tool for influencing dyadic cooperative investments, but measuring prior social relationships may be necessary to interpret the results of hormonal manipulations of cooperative behavior and it may be difficult to alter partner choice in vampire bats using intranasal OT alone., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Acquiring information via observation of others can be an efficient way to respond to changing situations or learn skills, particularly for inexperienced individuals. Many bat species are gregarious, yet few studies have investigated their capacity for learning from conspecifics. We tested whether big brown bats (Eptesicus fuscus) can learn a novel foraging task by interacting with knowledgeable conspecifics. In experimental trials 11 naïve bats (7 juveniles, 4 adults) interacted freely with trained bats that were capturing tethered mealworms, while in control trials 11 naïve bats (7 juveniles, 4 adults) flew with untrained bats. Naïve bats were then assessed for their ability to capture tethered mealworms. While no bat in the control group learned the task, a significant number of experimental bats, including juveniles with little or no experience foraging, showed evidence of learning. Eighty-two per cent of experimental bats and 27% of control bats directed feeding buzzes (echolocation calls associated with prey capture) at the mealworm. Furthermore, seven experimental bats (64%) showed evidence of learning by attacking and/or capturing the mealworm, while no bat in the control group attacked or captured the prey. Analyses of high-speed stereo video recordings revealed increased interaction with demonstrators among bats attacking or capturing the mealworm. At the time they displayed evidence of learning, bats flew closer together during feeding buzzes than during other portions of trials. Our results demonstrate that social interaction with experienced bats, and listening to feeding buzzes in particular, may play an integral role in development of foraging skills in bats.

In colonial species, recognition of offspring should be under strong selection. For accurate identification to occur offspring must emit individually distinctive signals and parents must be able to discriminate between signals. Female greater spear-nosed bats (Phyllostomus hastatus) roost in stable social groups and use infant vocalizations, termed isolation calls, to locate and identify their young. In this study, we investigate both the production and perception of isolation calls in P. hastatus. First, we measured acoustic features and found that after controlling for ontogenetic effects, sufficient variation exists between pups for isolation calls to function as individual signatures. Moreover, pups from the same social group emit calls with more similar spectral and spectro-temporal features than pups from different social groups, indicating that these features are likely heritable. We used psychoacoustic experiments in the laboratory to determine if adult females could discriminate between calls from pups in the same or different social group. Females discriminated between pups when faced with a template-matching task and their performance was correlated with the salience of spectral and spectro-temporal features. We found no difference in performance when females had to discriminate between pups from the same and different social groups. These results indicate that females should be able to accurately identify their young using isolation calls.