Geographic variation in the morphology, echolocation and diet of the little free-tailed bat, Chaerephon pumilus (Molossidae)

Abstract

The insectivorous bat Chaerephon pumilus has a wide distribution in Africa and displays considerable variation in the colour of its wings and venter.We investigated whether variation is also evident in its morphology, echolocation and diet by comparing a population of this species in Amani Nature Reserve, Tanzania, with published data for these characters elsewhere in its range. Chaerephon pumilus in Amani is on average larger than individuals of this species elsewhere in its range. The Amani population has a longer mean forearm (39.1 ± 3.3mm)than populations in Ghana (36.4 ± 1.0 mm) and southern Africa (38 mm) and a higher wing loading (15.3 ± 2.2 N/m²) than populations in South Africa (mean = 12.6 N/m²). Its echolocation calls are of lower minimum, maximum and peak frequency but of a longer inter-pulse interval than in South Africa. As in other parts of its range, the Amani bats ate small insects ranging in body length from 3–8 mm. However, the most notable difference in the diet of the Amani population was the consumption of cockroaches (Blattodea: Blaberidae) which comprised more than 60% of the diet. These cockroaches shared the roost with the bats and the bats probably used vision to detect and capture the cockroaches by crawling on the rafters supporting the roof of the roost. Elsewhere in its range the diet of C. pumilus is dominated by Coleoptera, Hemiptera and Diptera.

Keywords: bat, echolocation, morphology, diet, cryptic species, cockroach