Assessing the impact of introduced cats on island biodiversity by combining dietary and movement analysis

Abstract

Populations of feral (not owned by humans) and domestic cats Felis catus coexist in most inhabited islands, and they have similar impacts on native species. Feral cats are generally believed to vary their diet according to prey availability; however, no previous studies of diet have tested this hypothesis on insular ecosystems with a limited range of available prey. Because domestic cats kill prey independently of hunger, the spatial extent of their impact on wildlife will be influenced by home-range size. In this study, we combined dietary information with cat movements to assess the impacts of feral and domestic cats on island biodiversity. We quantified the diet of cats from scat samples collected across one year and tested whether diet varies by season. The abundance of main prey categories was also estimated to document seasonal variation in prey availability for cats. Finally, we tracked domestic cats by global positioning system units in all four seasons to examine whether home-range patterns varied seasonally. The diet of cats constituted three prey groups (rodents, birds and invertebrates), and the seasonal variation in consumption of each taxon matched the seasonal variation in prey availability, thus supporting the generalist behaviour of cats on oceanic islands. Roaming behaviour varied among individuals and across seasons, but could not be explained by availability of prey. Unconfined cats had larger homeranges than confined cats, but most domestic cats strayed <1 km from home. Thus, confinement of domestic cats might reduce the spatial extent of cat impact on native prey populations on oceanic islands.

The unnoticed effect of a top predator on complex mutualistic ecological interactions

“…In these micro-sites they find suitable places to dig their characteristic defecation hollows. Therefore, invasive cats appear to produce a clearly different seed-shadow than the native lizards, because domestic cats usually range over much wider areas (0.5-20.3 ha; Hervías et al 2014). Although cats can certainly disperse seeds further than lizards (home area: 15.00-89.26 m 2 ; Molina Borja 1985), longdistance dispersal in this xeric habitat is ensured by the participation of the native predators L. meridionalis and F. tinnunculus.…”

Mortality due to trauma in cats attending veterinary practices in central and south‐east England

“…The current study found no evidence that neuter status was associated with the risk of mortality due to RTA or trauma in cats aged older than six months. Studies of free‐ranging cats suggest that entire cats have larger home ranges than those that are neutered (Hervías et al , Kitts‐Morgan et al ). If this is also the case for owned cats, it would appear that the distance that cats roam is not related to their risk of trauma or RTA.…”

Habitat‐specific effectiveness of feral cat control for the conservation of an endemic ground‐nesting bird species

“…; Hervías et al . ). Feral cats in the semi‐desert may consume mostly mice and rabbits, while cats in pastures may consume mostly rodents, and it is therefore plausible that cat control did not lead to a strong increase of rats in the semi‐desert because rats were more limited by available food resources than by cat predation.…”

“…In addition, foraging preferences of feral cats may have differed between the two habitats owing to a different prey community composition. Cats are generally considered opportunistic foragers that consume the most available prey in each habitat and on each island (Bonnaud et al 2010;Herv ıas et al 2014). Feral cats in the semi-desert may consume mostly mice and rabbits, while cats in pastures may consume mostly rodents, and it is therefore plausible that cat control did not lead to a strong increase of rats in the semi-desert because rats were more limited by available food resources than by cat predation.…”