Invasive predators threaten biodiversity worldwide, and generalist invasive predators are often more successful due to their broad diets. Predation patterns can be influenced by prey abundance, prey preference, and climate, and understanding these relationships is integral to conserving native prey species. We examined stomach contents of 2882 feral cats Felis catus from San Clemente Island, California, to assess how their diets varied annually and seasonally, and how precipitation and prey abundance influenced predation patterns. Rodents were found in 95% (n = 2589) of stomachs containing prey. The endemic San Clemente deer mouse Peromyscus maniculatus clementis was the most prevalent prey species and was found in 85% (n = 2589) of stomachs containing prey. Consumption of rodents, lizards, and birds varied annually. In years following dry winters, consumption of rodents decreased and consumption of lizards increased. This had a particularly strong effect on endemic night lizards Xantusia riversiana reticulata with 20.4% (n = 1952) of non-empty cat stomachs containing night lizards following normal years, and 43.7% (n = 602) following dry years. Consumption of rodents peaked in fall, while consumption of lizards and birds peaked in spring. Using rodenticide removed from bait stations as an index of rodent abundance, we found a positive correlation between bait removal and the number of rodents consumed by cats, and a negative correlation between bait removal and the number of lizards consumed by cats. These results suggest that feral cats use rodents as primary prey and lizards as secondary prey, particularly during droughts when rodent abundance is low. Understanding how weather patterns affect invasive species predation patterns will help conservation biologists predict and manage for the effects of invasive species as climate change continues. Furthermore, identifying and quantifying diet pattern seasonality can help managers identify times when sensitive species are vulnerable and plan interventions accordingly.Animal Conservation 23 (2020) 60-71 ª

Feral cats, Felis catus, inhabiting San Clemente Island, California, are both predators and competitors of multiple sympatric endemic species. To improve our understanding and management of these invasive predators, we used GPS-equipped radiocollars to track 11 (6F:5M) cats for a total of 3,108 days, resulting in 15,419 GPS locations. Average 100% minimum convex polygon, 95% kernel density, and 50% kernel density estimates were 229, 132, and 33 ha, respectively. The point estimate for average male home-range size was larger than the average for females, but there was substantial variation among individuals of both sexes. Overlap indices indicated similar usage areas during nocturnal and diurnal time periods. Sample size limited our ability to definitively detect habitat preference, but data suggested areas within 50 m of roads were avoided, and that thicker land cover was preferred over open grasslands. Three test collars deployed within active cat home ranges indicated GPS locations were precise, with 96% of locations having < 10-m error estimates, and that horizontal dilution of precision indices were not useful in screening data. Our results describe feral cat spatial ecology on a semiarid island and can be used to inform population estimation, control, and mitigation programs.

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Wildlife-aircraft collisions (wildlife strikes) pose a serious safety risk to aircraft. Raptors (i.e., hawks and owls) are one of the most frequently struck guilds of birds within North America. Integrated wildlife damage management programs combine a variety of non-lethal and lethal management tools to reduce presence of raptors on airports. Live-capture and translocation away from an airport is a commonly used non-lethal method to reduce the risk of raptor-aircraft collisions. In southern California, USDA Wildlife Services airport biologists live-captured, marked with auxiliary markers (i.e., airport program-specific plastic leg band), and translocated approximately 1,232 raptors from seven airports and military bases located within the highly urbanized environment of the Los Angeles Basin during January of 2010-December of 2016. Ten different raptor species were marked and relocated during this effort. The composition of translocated raptors was red-tailed hawks (38.9%), Cooper's hawks (27.5%), American kestrels (20.7%), barn owls (7.4%), and great horned owls (3.7%). Overall, the percentage of translocated raptors that returned to an airport was 11.1%. Although research is needed to better understand and increase the efficacy of such management efforts, this non-lethal method of reducing the presence of individual raptors at airports in southern California will be an important component of future wildlife management programs.