Olfactory discrimination ability of the short-nosed fruit bat Cynopterus sphinx

Abstract

We carried out a set of experiments on a megachiropteran bat Cynopterus sphinx to examine its olfactory discrimination ability to a variety of food odor substances. We used seven undiluted odorants such as isoamyl acetate, ethyl acetate, hexanol, benzaldehyde, limonene, pinene, and dimethyl disulfide for odor discrimination experiments. These volatile substances are present at various quantities in the natural food (fruits and nectar) of C. sphinx. Equal amount (200 μl) of seven odor substances kept individually but simultaneously in seven of eight specimen tubes which were equipped in a radially and horizontally arranged experimental set-up. In addition to the odorants, about 5 mm pieces of any one of the fruits such as guava, papaya and sapota were offered in cups as reward to the bats. The behavior of bats was observed visually and number of bat-visits to the odorants, and to the scentless control was continuously recorded in an event recorder. The mean number of approaches made by the bats differed across the odorants and scentless control (χ² = 34.94, d.f. = 7, P < 0.001). Bats made relatively more number of visits to the odorants compared to the control, except hexanol and dimethyl disulfide. Among the odor substances, bat-visits and preference factor showed a gradational pattern with relatively maximum to ethyl acetate and minimum to dimethyl disulfide. The pattern of bat-visits was bimodal to benzaldehyde and dimethyl disulfide, whereas it was unimodal to all the remaining five odorants. Our study suggests that C. sphinx is able to discriminate different odor substances in a complex olfactory environment.