Loud calls ofGalago crassicaudatus andG. garnettii and their relation to habitat structure

Long distance vocalizations have been shown to be good indicators of genetic species in primates. Here the loud calls of two recently identified greater galago taxa —Galago crassicaudatus andG. garnettii — are compared and analyzed statistically. Observed differences in call structures are investigated further as potential indicators of differences in the structures of habitats frequented by the two species. Although the calls share a repetitive structure, and show similar dominant frequency bands (1,000 – 1,500 Hz), they differ significantly in the number of units per call, unit duration, inter-unit interval, highest frequency, lowest frequency, dominant frequency band, first harmonic, and call duration. The duration of theG. crassicaudatus call is more than twice that ofG. garnettii. Strong intraspecific consistency is seen in the most energetic frequency bands (dominant frequency band and first harmonic), and durations of the individual units and inter-unit intervals. Information important to species recognition is thus most likely to be contained in these features. Individual recognition may be encoded in the relative emphasis of higher level harmonics. The frequency structures of the calls will reflect requirements for acoustical transmission in a forest environment, as well as structural constraints imposed by body size. Higher frequencies detected in theG. garnettii call (up to 8,500 Hz) may have a functional significance related to distance estimation, or may simply be a reflection of smaller body size. The greater modulation of theG. garnettii call suggests that its habitat constitutes a denser or more turbulent medium for sound transmission than does the habitat ofG. crassicaudatus.