rabbit and house mouse, and on native rodents and marsupials, particularly the common ringtail possum. In the United States some people advocate for feral cats as a means to control pigeons and invasive rodents like the house mouse and brown rat, however these cosmopolitan species co-evolved with cats in human-disturbed environments, and so have an advantage over native rodents in evading cat predation. Studies in California showed that 67% of the mice killed by cats were native species, and that areas near feral cat colonies actually have larger house mouse populations, but fewer birds and native rodents. Though cats usually prey on animals less than half their size, a feral cat in Australia was photographed killing an adult pademelon of around the cat's weight at . African feral cats have been observed directly pilfering milk from the elephant seal's teat. Predators Feral cats are prey of feral dogs, dingoes, coyotes, caracals and birds of prey. Health Life span and survival Without human assistance Adult feral cats without human assistance have been found in surprisingly good condition. In Florida, a study of feral cats admitted to a trap-neuter-return (TNR) program concluded that "euthanasia for debilitated cats for humane reasons is rarely necessary". A further study of over 100,000 feral and stray cats admitted to TNR programs in diverse locations of the U.S. resulted in the same 0.4% rate of euthanasia for debilitating conditions. The body condition of feral cats entering a TNR program in Florida was described as "generally lean but not emaciated". However, many feral cats had suffered from parasites such as fleas and ear mites before entering TNR programs. With human assistance Feral cats in managed colonies can live long lives. A number of cats in managed colonies in the United Kingdom died of old age. A long-term study of a trap-neuter-return (TNR) program on a university campus in Central Florida found that, despite widespread concern about the welfare of free-roaming cats, 83% of the cats studied had been present for more than six years, with almost half first observed as adults of unknown age. The authors compared this result to a 1984 study that found the mean life span for domesticated cats was 7.1 years. Disease Types Feral cats, as with all cats, are susceptible to diseases and infections including rabies, bartonellosis, toxoplasmosis, feline panleukopenia virus, external and internal parasites, feline immunodeficiency virus (FIV), feline leukemia virus (FeLV),