Effect of house cats, being fed in parks, on California birds and rodents

Increasingly, cat (Felis catus) advocates are establishing feeding stations or cat colonies in public parks and often claim that the well-fed cats pose little threat to wildlife populations. This claim was tested on East Bay Regional Park District land east of San Francisco, California during 1995 and 1996. Rodents were livetrapped on 100-trap grids for 8 nights at 9 sites (5 in 1995) in a no cat area and 9 sites (5 in 1995) in a cat area. Bird surveys, 6 in each area in 1995 and 8 in each area in 1996, were conducted along 2.2km transects. The number of cats seen in the 2 areas differed both years (P<0.0001). In 1995, more harvest mice (Reithrodontomys megalotis) were trapped in the no cat area (P=0.022) whereas the numbers of deer mice (Peromyscus sp.) (P=0.207), house mice (Mus musculus) (P=0.257), and California voles (Microtus californicus) (P=0.362) trapped were not different in the cat and no cat areas. In 1996, more harvest mice (P=0.0003) and deer mice (P=0.019) were trapped in the no cat area, more house mice (Mus musculus) were trapped in the cat area (P=0.008), and the numbers of California meadow voles (P=0.838) trapped were not different between areas. More native rodents were trapped in the no cat area both years, 1995 (P=0.033), 1996 (P=0.005). Over 85% of the deer mice and the harvest mice trapped occurred in the no cat area and 79% of the house mice trapped were in the cat area. Birds that were resident year-round were seen more often in the no cat area(P=0.009). California quail (Callipepla californicus) (P < 0.0001) and California thrashers (Toxostoma redivivum) (P=0.002) were more likely to be seen on a survey in the no cat area than in the cat area.