In the early 1970s humane advocates started mass spay - neuter campaigns, which by the year 2000 had greatly decreased the population of free - roaming dogs. (outthefrontdoor.com)
Additionally, removing enough of any predator to decrease their population size is quite difficult. (aspca.org)
This solution successfully decreases the population, reduces birth rates and improves the overall health of the colony. (ocgainesville.org)