Keystone resource (Ficus) chemistry explains lick visitation by frugivorous bats
2012
Bravo, Adriana | Harms, Kyle E. | Emmons, Louise H.
Geophagy is a widespread behavior among plant-eating animals. In the Neotropics, mineral licks are activity hot spots for frugivorous bats (Stenodermatinae). Bats drink mineral-rich water accumulated in soil depressions made by geophagous mammals. Two mechanistic hypotheses have been proposed to explain this behavior: licks are reliable sources of limiting nutrients, especially sodium; and licks provide substances that render dietary toxins less harmful. We assessed the former by examining bats' diets in conjunction with lick chemistry in the Peruvian Amazon. We found that most bats that visit licks belong to the subfamily Stenodermatinae and are specialists on Ficus fruits—a keystone resource. In addition, although Ficus fruits are good sources of some minerals, their sodium content is limited in relation to the physiological requirement of a small mammal. In contrast, bats of the subfamily Carolliinae supplement their fruit diets with insects, potential sources of sodium. Complementary results among diets, Ficus chemistry, and lick-water chemistry strongly support the sodium-limitation hypothesis for bat lick use and suggest a mechanistic link between bats and ecosystem engineers that make soil-borne resources available. Because sodium is an essential nutrient for vertebrates and Ficus is a keystone resource for many animal species, our results may have implications for the community of frugivorous vertebrates in areas where sodium is limited. Licks may play a critical role as sodium sources and thus they should be considered as important conservation targets.
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