TNR as a humane method of controlling feral cat populations. In the U.S., the practice is endorsed by the Humane Society of the United States. and the National Animal Control Association, TNR is opposed by the Australian Veterinary Association, the National Audubon Society, the National Wildlife Federation, the Cornell Lab of Ornithology, the American Association of Wildlife Veterinarians, the Wildlife Society, the American Bird Conservancy, and PETA. Some U.S. military bases have TNR programs, but the United States Navy prohibits such programs on Navy land. The American Veterinary Medical Association (AVMA), in 2016, adopted a resolution that "encourages collaborative efforts to identify humane and effective alternatives to the destruction of healthy cats for animal control purposes, while minimizing their negative impact on native wildlife and public health." The AVMA voiced support for "properly managed [feral cat] colonies" outside "wildlife-sensitive ecosystems" but stated that "[t]he goal of colony management should be continual reduction and eventual elimination of the colony through attrition." The AVMA stated that "free-roaming abandoned and feral cats that are not in properly managed colonies should be removed from their environment and treated in the same manner as other abandoned and stray animals in accordance with local and state ordinances" and that "[f]or colonies not achieving attrition and posing active threats to the area in which they are residing, the AVMA does not oppose the consideration of euthanasia when conducted by qualified personnel, using appropriate humane methods as described in the AVMA Guidelines for the Euthanasia of Animals." The effectiveness of both trap-and-euthanise and TNR programmes is largely dependent upon controlling immigration of cats into cleared or controlled areas; where immigration of new cats is controlled both techniques can be effective. However where immigration is not controlled culling is more effective. Comparisons of different techniques have also found that trap-and-euthanise programmes are half the cost of TNR ones. An analysis of both techniques in Hawaii suggested they are less effective when new cats were introduced by the abandonment of pets. The usefulness of TNR is disputed by some scientists and conservation specialists, who argue that TNR is only concerned with cat welfare and ignores the ongoing damage caused by feeding outdoor populations of neutered cats, including the depredation of wildlife, transmission of diseases, and the accumulation of cat faeces in the environment. Conservation scientists also question the effectiveness of TNR at controlling numbers of feral cats. Some studies that