The City of Charlotte, NC, in attempting to determine the best kind of program for reducing its increasing populations of unwanted dogs and cats, examined a full range of possible options for limiting these populations. Five measures for population control were considered: spay/neuter surgery, euthanasia, physical restraint, mechanical contraception, and chemical contraception. It was concluded that a spay/neuter program that incorporated educational and legislative components would be the most effective means of large-scale population control, although other methods like euthanasia would still have to be used. Based on a survey of a number of cities with spay/neuter programs in place, it was found that a municipally run clinic for such surgery, with no excluding criteria related to income of clients, offered the best hope for limiting the future numbers of stray and unwanted animals.
Quisenberry, D., & Clapp, M.E. (1983). Selecting a spay/neuter program for animal control in city of Charlotte. International Journal for the Study of Animal Problems, 4(3), 214-225.