The FWC estimates there are between 6.3 and 9.6 million feral cats (Felis catus) in Florida (at http://www.floridaconservation.org), which, conservatively, kill millions of small animals in Florida each year (FCIT 2003). Feral cats are generally harmful to native fauna throughout the state, because even cats well-maintained as pets take a high toll of nearby small animals (Churcher and Lawton 1987, Lepcyzk et al. 2003, Woods et al. 2003), especially considering cats continue to hunt and kill when not hungry (Liberg 1984). Globally, feral cats feed heavily on small vertebrates and have led to the extinctions of a number of species (e.g., Burbidge and Manly 2002, Nogales et al. 2003). Feral cats in Florida have been observed to prey on loggerhead (Caretta caretta) and green (Chelonia mydas) sea turtles, roseate tern (Sterna dougallii), least tern (Sterna antillarum), American oystercatcher (Haematopus ullietus), Florida scrub jay (Aphelocoma coerulescens), Choctawhatchee beach mouse (Peromyscus poloionotus allophrys), Anastasia Island beach mouse (Peromyscus gossypinus gossypinus), Key Largo cotton mouse (Peromyscus gossypinus allapaticola), Southeastern beach mouse (Peromyscus poloionotus niveiventris), Perdido Key beach mouse (Peromyscus poloionotus trissyllepsis), Key Largo woodrat (Neotoma floridana smalli), Lower Keys marsh rabbit (Sylvilagus palustris hefneri), all federally listed as threatened or endangered (FCIT 2003, Ferriter et al. 2008). Cat removal has been demonstrated to result in immediate rebounds of endangered beach mouse populations (FCIT 2003).
While cats are harmful to wildlife throughout Florida, they are of the particular concern on the islands of the Florida Keys (Ferriter et al. 2008). They have been a factor in the 50% decline in populations of the endangered Lower Keys marsh rabbit (Forys and Humphrey 1999) and cat removal was identified as an integral component in the recovery of Key Largo woodrat (USFWS 1999, 2003). Making matters worse, feral cat colonies can concentrate a large number of instinctive predators in an area and pose significant threats to the smaller fauna in the vicinity. For example, the Ocean Reef Cat Club (ORCAT) at the exclusive Ocean Reef Club residential resort on Key Largo maintains a large feral cat colony adjacent to the federal and state lands supporting the Key Largo woodrat and Key Largo cotton mouse. Despite the protected habitat, the Key Largo woodrat population dropped from 6500 in 1988 to less than 80 animals by the early 2000s (Humphrey 1988, Winter 2004, B. Muiznieks pers. comm.). ORCAT runs an intensive, well-funded trap, neuter and release (TNR) program (Clark and Pacin 2002), but TNR programs are not effective for managing feral cat populations under most circumstances (e.g., Anderson et al. 2004, FCIT 2003, Ferriter et al. 2008, Jessup 2004). The ORCAT colony continues to have around 500 cats neighboring endangered species habitat despite the intensive TNR efforts. Luckily, captive breeding is now helping replenish the Key Largo woodrat population.
Feral and free-ranging cats are notorious for their destruction of avifauna, and this problem is particularly pronounced in Florida where there are large numbers of cats often in the immediate vicinity of small forest remnants and hammocks that migrant birds rely on as migration stopover sites (Winter and Wallace 2006). For example, severe weather in spring 2001 resulted in a massive fallout of migrating warblers in the Keys, where large numbers of the birds were lost to predation by cats (Winter and Wallace 2006). Similarly, the decline of upland bird populations between 1988 and 1998 at Greynolds Park (Miami-Dade County)
was due to a cat colony in the park. The problem was rectified by stricter laws against abandoning or feeding cats, and removal of the existing cats (Winter and Wallace 2006).
Beyond their environmental impacts, feral cats, especially in dense colonies, present human and wildlife disease concerns. While cats can carry a host of diseases and parasites, rabies is the greatest concern. Cats are the most frequently reported domestic animal in the U.S. with rabies (e.g., Barrows 2004). For example, between 1988 and 2003, there were 208 laboratory confirmed diagnoses of cats with rabies in Florida (Barrows 2004). In fact, the Florida Rabies Advisory Committee stated "the concept of managing free-roaming/feral cats is not tenable on public health grounds because of the persistent threat posed to communities from injury and disease" (Barrows 2004, Brooks 1999).
While the threats cats pose to native wildlife, especially endangered species, and the disease concerns are well-documented, removal of feral cats, particularly at cat colonies, is often accompanied by vocal public outcry from cat enthusiasts. The efforts to protect highly endangered species in the Florida Keys from predation by cats are noteworthy examples. These programs did not involve the lethal removal of animals. Rather, feral cat removal involved live trapping and turning cats over to animal shelters. Despite that, opposition to cat removal has been stiff (including sabotage of traps) and has affected management of the endangered species. Thus, feral cats, in particular, can present additional social dimensions creating difficulties for effective population management.
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