Temporal Variation in Fruit Bats Observed during Daytime Surveys in American Samoa

• Published in: Wildlife Society bulletin Vol. 23; no. 1; pp. 36 - 40
• Main Authors: Morrell, Thomas E., Craig, Peter
• Format: Journal Article
• Language: English
• Published: Bethesda The Wildlife Society 01-04-1995; Blackwell Publishing Ltd
• Subjects: Aerial locomotion; Animal behavior; Bats; Biology; Bird songs; Endangered species; Plants; Rain forests; Topographic surveys; Vehicular flight; Wildlife biology; American Samoa
• ISSN: 0091-7648; 1938-5463

We conducted daytime surveys of Samoan and Tongan fruit bats (Pteropus samoensis and P. tonganus) to examine temporal patterns of fruit bat detections on Tutuila Island, American Samoa. The greatest numbers of bats were observed during early morning and late afternoon. Variation in numbers of bats observed during 20-minute periods within and among days was often extreme. However, mean number of bats observed during early and late periods stabilized by the tenth randomly selected period. Despite a small sample size, our findings suggest that surveys to estimate relative abundance of fruit bats should use a repeated design to reduce sample bias. Furthermore, because of variation in bats counted among periods, any trend analysis based on a single visit to a survey site may be misleading. The recommended survey technique provides an efficient method to conduct daytime surveys of fruit bats on Pacific islands with considerable topographic relief. Because the technique is standardized and all flying bats in the study area are observed, survey results can be statistically compared, thereby making it useful to monitor seasonal and annual trends in bat numbers.