Geophagy by the Indian short-nosed fruit bat, Cynopterus sphinx (Pteropodidae) while foraging on Madhuca latifolia (Sapotaceae) in Tamil Nadu, South India

Abstract

Geophagy has been reported in many mammals and birds. However, in pteropodid bats, this behaviour has not been reported. Here, we document geophagy behaviour by the pteropodid bat, Cynopterus sphinx, during foraging in the fruiting trees of Madhuca latifolia (Sapotaceae). These bats removed single fruits from the foraging tree and carried it to the feeding roost for consumption. At around 1900 h, we observed three individuals of C. sphinx gleaning over the ground surface by circling flights. The bats landed with their wings spread apart and started licking the soil with head movements. Their ventral body surface rested completely on the ground while consuming the soil. A total of 91 feeding bouts of soil consumption were recorded within 1 h; however, thereafter, this behaviour was not observed. In order to understand the function of geophagy, we quantitatively analysed the composition of minerals in the soil, as well as in the M. latifolia fruits (partially ripe) along with its secondary metabolites from the study site. Our results revealed that the partially ripe fruits contained high levels of secondary metabolites (alkaloids, tannins, coumarins and saponins). The soil contained higher levels of Mg, Ca, Fe, Na and K minerals than the fruits. These findings suggest that bats may gain essential minerals that are low in their fruit diet by consuming soil. In addition, the observed minerals that play a role in detoxification of the secondary metabolites present in the partially ripe fruits that might be detrimental to the consuming bats. Frugivory, nectarivory and folivory are well understood in C. sphinx; however, geophagy behaviour has not been reported in this species so far. This may represent an ‘adaptive behavioural plasticity’ in the foraging behaviour of the observed C. sphinx population.