Context-specific alarm calls of the eastern chipmunk, Tamias striatus

The structure and context of alarm calls produced by chipmunks (Tamias striatus) at a field site in southern Quebec were recorded during opportunistic field observations and experimentally simulated hawk attacks. Chipmunks produced three call types in the presence of predators. Chipping consisted of a series of high frequency notes with a rapid downward frequency slope (9.6 to 2.8 kHz) and was given in the presence of mammalian predators by chipmunks perched on a raised vantage point. Chucking consisted of a series of lower frequency notes also sloping downwards (2.5 to 0.4 kHz), given in the presence of avian predators by perched animals. The trill was a lower amplitude, multi-note call usually given only once by animals before reaching a refuge while fleeing from either type of predator. The average trill contained 6–11 downward sloping notes (7.3 to 0.8 kHz). The alarm call types of eastern chipmunks appear to be similar to those reported for western chipmunks. However, they differ in the clear separation of the calls for aerial and terrestrial predators. Chipmunks differ from most other terrestrial sciurids in giving repeated calls for aerial as well as terrestrial predators and in using a call just before reaching a secure refuge.

Effect of motivational context on conspecific song discrimination by brown-headed cowbirds (Molothrus ater)

Two experiments to examine the effects of motivational context on the perception of conspecific song by cowbirds were conducted. In the first experiment, sexual displays were elicited from females by playback of normal song and rearranged sequences of the component phrases. In a second experiment, male and female cowbirds discriminated among the same songs in a food-rewarded operant procedure. In a sexual context, the birds were sensitive to both the beginning and end phrases of normal song, whereas in a food context, the birds were more sensitive to the beginning of normal song. In both experiments, one-phase songs were better discriminated from normal song than two-phrase songs, and there was no effect of phrase order on discrimination. Similarities and differences in the results of the two experiments suggest that some aspects of cowbird song perception remain constant across motivational contexts, whereas others are unique to particular motivational contexts.

Use of male blue monkey "Pyow" calls for long-term individual identification

This study examines whether individual adult male blue monkeys (Cercopithecus mitis stuhlmanni) can be identified through acoustic analysis of their "pyow" calls. It is possible to reliably assign the pyow call of the blue monkeys of Kibale Forest, Uganda, to the individual caller based on the acoustic properties of the vocalization. Analysis of pyows made by a recognizable male over a 10-yr period shows that the acoustic properties of one individual's pyow call can remain relatively constant over time. Acoustic analysis of pyow calls may provide a relatively easy and reliable method to document tenure lengths of adult male blue monkeys resident in groups. Similar analyses of the loud calls of other species of primates may, likewise, prove to be useful in documenting long-term membership. © 1992 Wiley-Liss, Inc.

Neighbour–stranger discrimination by song in the veery, a species with song repertoires

Territorial male veeries (Catharus fuscescens) responded much more to playback of song repertoires from strangers than of those from territorial neighbours. Previous experimental work on species that possess song repertoires has demonstrated only weak neighbour–stranger discrimination. These earlier studies, however, employed only one or two song types, which constituted only a fraction of the repertoires of these species. We used the entire repertoires for playback, these varying from one to three song types. The strong discrimination we demonstrate here is interpreted as evidence that repertoires are not detrimental to recognition by song in veeries. Recordings of song sequences from some individuals consistently evoked a stronger response than did those of others. These differences in response were not related to the number of song types, the number of versions of any one song type, nor to the quality of recording presented.