Effects of the temperature on activity patterns and torpor in Saccolaimus saccolaimus in Bangladesh with notes on its morphometrics and roosting behaviour

Abstract

Saccolaimus saccolaimus is one of the six Emballonurid bats and the only species from the genus Saccolaimus that occurs in South and Southeast Asia. This species utilizes tree hollows, damaged palm trees, and occasionally artificial structures as roosts. We recorded a total of 22 bats from 10 colonies located at two dormitories in Jahangirnagar University (JU) in a sub-urban setting in central Bangladesh. The number of bats per colony varied between 1-9 individuals, with an average of four bats per colony. We found that the colonies of S. saccolaimus emerged from roosting sites when the temperature was 22.5°C or higher. The highest bat activity was recorded in September (79.66 mins) when the air temperature was 27.66°C, and the lowest was in January (47.01 mins) when the air temperature was 17.46°C. We observed variations in bat activity in different months, and bat activity was strongly correlated (R-square = 0.52) with air temperature. The most extended torpor period for the colonies was recorded for 27 days. The mean weight for male S. saccolaimus in JU was 41.66 ± 0.29 (41.46-42) g, whereas for females was 45.32 ± 3.08 (43.14- 47.5) g. Although some variation was observed in the morphological measurements, the morphometric analysis indicated no significant differences between specimens from Bangladesh and the neighbouring countries. Further research is needed to understand various ecological aspects of S. saccolaimus in Bangladesh. Therefore, to do so, the existing colonies on JU campus should be extensively monitored.