Predation by Free-Roaming Cats on an Insular Population of Bats

Abstract

Free-roaming cats are known to adversely impact native faunas in the areas where they have been introduced, an impact that is even greater on islands. We examine the predation of bats by cats at Culebrones cave, Puerto Rico, West Indies. Culebrones cave is a hot cave located in the karst region of northern Puerto Rico. The temperature gradient inside the cave sustains a multi-species assemblage of bats consisting of approximately 300,000 individuals of six species, namely: Brachyphylla cavernarum, Erophylla bombifrons, Monophyllus redmani, Mormoops blainvillei, Pteronotus quadridens and Pteronotus parnellii. Even though rats are often their primary prey, cats will use alternative prey, which enables them to maintain their abundance when one prey is not available. In Puerto Rico, birds and reptiles are known to be preyed upon by cats. Although cats are commonly observed in or around bat caves in Puerto Rico, this is the first systematic attempt to evaluate their role as bat predators. We made observations of the hunting strategy of cats using an infrared camera and recorded the number of wings left as remains of these hunting bouts. Wings were identified to species. Cat scats were also recovered and examined to identify prey species. Our results suggest that captures of different species of bats is not a function of their abundance in the cave. While M. blainvillei (11 g) and P. quadridens (5 g) are the most abundant species in the cave, B. cavernarum (50 g) and M. redmani (11 g) are captured in greater numbers by the cats.