A Global Systematic Review and Meta-Analysis of Methods Used to Evaluate Predation and Diet of Domestic Cats (Felis catus)

Abstract

Invasive species, including multiple domestic species, can devastate local biodiversity. Domestic cats (Felis catus) can cause declines in select prey species around the world, and multiple methods are employed to monitor cat diet and predatory habits. These methods have not yet been compared against one another in a meta-analytical way, and therefore, the aim here was to evaluate the relative proportions of different taxa reported in the cat diet. We compared 88 studies using a beta regression model conducted on four different taxa, where methodology, location and duration of study were included as variables. Mammals were further divided into rodents, insectivores and medium-sized mammals for a subset of European studies, using Wilcoxon Rank Sum tests to compare methods. Proportions of mammals were lowest, and those of herptiles were highest in studies using collar-mounted cameras. However, greater proportions of birds were recorded in return questionnaires, suggesting detectability bias, as bird remains are easier to detect. Mammal figures were lower in Australasian studies, whereas birds were more frequently reported in Australasia than in other mainland locations, likely reflecting a difference in prey availability. In Europe, insectivores were found to be more frequently returned than eaten, supporting the existing hypothesis that this group is largely unpalatable to cats. Care should be taken when extrapolating data gathered by different methods, as each one fundamentally measures a different aspect of diet. Only six (6.8%) studies here used video cameras and, although a useful monitoring technique, video results showed a different pattern in taxonomic proportions to data gathered using consumed or returned prey. More research using cat cameras in locations of varying faunal composition is necessary, improving the general applicability of video data to cat populations globally. Palatability and detectability of prey appear to influence the data reported, and these aspects should be considered when calculating total predation rates.