Seasonal intake responses could reflect digestive plasticity in the nectar-feeding bat Anoura geoffroyi

Abstract

Many studies have used intake response as a tool for understanding digestive capacities of bats to process nectar. Nevertheless, most of them have been done so in one season, assuming that this response does not change over the year. One study performed with Glossophaga soricina, a bat inhabiting warm environments, found different intake response over seasons, but these changes are unknown for other bat species; especially those inhabiting cold climates. We measured changes in volumetric intake of Anoura geoffroyi (found in places above 2, 500 m a.s.l.) feeding on sucrose concentrations ranging from 5 to 35% (wt./vol.) in spring and compared the results with those previously published for winter. Because of differences in ambient temperature and nectar availability in the places they inhabit, we predicted different intake responses among seasons. We found differences in intake responses between winter and spring. Constant energy intake in winter was 101.07 ± 5.4 kJ, and decreased from 23 to 37% in spring. Body mass gain in winter was 1.31 ± 0.1 g, and was reduced from 56 to 74% in spring, when bats fed on sugar concentrations of 15 and 5%. Seasonal differences in intake responses and body mass changes provide evidence of digestive plasticity, which may have important ecological implications for bats. Species able to change their digestive traits would have the capacity to change their food intake depending on the energy demands imposed by their environment, while those with low plasticity should change their behavioral and energy-saving strategies when confronting changes in the abundance or the nutritional quality of the nectar they consume.