The spatial ecology of invasive feral cats Felis catus on San Cristóbal, Galápagos: first insights from GPS collars

Abstract: The dangers posed by invasive species for endemic island wildlife are well recognised. Introduced domestic cats (Felis catus) represent a significant threat to several endemic species of the Galápagos archipelago—including hatchling marine iguanas (Amblyrhynchus cristatus) and potentially green turtles (Chelonia mydas)—yet little is known about their spatial ecology and habitat use on these islands. Here, we describe a pilot study using GPS collars to track the movements of three feral cats at a site of conservation interest on San Cristóbal Island. Based on 175 days of GPS data, we undertook spatial analyses to ascertain home ranges, and to investigate the overlap of ranges between the cats and potential prey species. Average home range was 1.27 km2 (1.12–1.46 km2), which—though small for feral cats—is in keeping with previous findings in Galápagos. We found the cats did use the habitat of a small marine iguana population but did not change their spatial habits before and after iguana hatchlings appeared. Changes over time in the daily movements of one cat indicated a possible response of the individual to the presence of hatchling green turtles (Chelonia mydas); though the data here are insufficient to show whether the cat was hunting these hatchlings. We recommend similar work be undertaken in areas with larger marine iguana populations, where hatchlings could represent a potentially important food source for invasive feral cats, as well as further work to determine the threat posed by cats to turtle hatchlings in Galápagos