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To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.anbehav.2006.09.003 Byline: Kirsten M. Bohn, Gerald S. Wilkinson, Cynthia F. Moss Abstract: In colonial species, recognition of offspring should be under strong selection. For accurate identification to occur, offspring must produce individually distinctive signals and parents must be able to discriminate between signals. Female greater spear-nosed bats roost in stable social groups and use infant vocalizations, termed isolation calls, to locate and identify their young. In this study, we investigated both the production and perception of isolation calls in P. hastatus. First, we measured acoustic features of calls and found that, after controlling for ontogenetic effects, sufficient variation exists between pups for isolation calls to function as individual signatures. Moreover, calls of pups from the same social group were more similar in spectral and spectrotemporal features than were calls of pups from different social groups, indicating that these features are probably heritable. We used psychoacoustic experiments in the laboratory to determine whether 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 spectrotemporal 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. Author Affiliation: (a) Department of Biology, University of Maryland, U.S.A. (a ) Department of Psychology, University of Maryland, U.S.A. Article History: Received 22 March 2006; Revised 18 May 2006; Accepted 5 September 2006 Article Note: (miscellaneous) MS. number: A10399

Female greater spear-nosed bats, Phyllostomus hastatus, can discriminate the calls of members of their own social groups but fail to discriminate individual calls based on field and laboratory playback studies using bat populations from three caves. The familiarity and discrimination of groupmates provide benefits to these bats in terms of sharing food resources and guarding feeding areas.

The social calls emitted by the greater spear-nosed bats, Phyllostomus hastatus are contact calls that coordinate foraging activities in this species. This is the conclusion drawn from seasonal observations and playback investigations undertaken in colonies in Trinidad, West Indies. The evidences that proved these screeches to be social calls in the greater spear-nosed bats are presented.

Investigations conducted on the vocalization of infant evening bats, Nycticeius humeralis, which possess distinct features that convey adequate information for a mother to locate her offspring in a colony, used seven acoustic variables, to accurately group all 306 isolation calls recorded from 39 pups in one attic nursery colony. The degree of among-bat variations in call variables remains unchanged for 14 days from birth. Isolation calls even have information regarding family identity.

The prey density, following behavior, spatial and temporal association among foraging flights and foraging success of evening bats were quantified to analyze information transfer. Observations of Nycticeius humeralis in northern Missouri showed that juvenile and some adult bats follow adult females to their roosting and feeding sites based on information exchange among nursery colony members. Roost exclusion experiment showed that bat vocalizations may be either active information exchange or alarm calls to facilitate group departures.