Population control

Population control can be influenced by a variety of factors. Humans can greatly influence the size of animal populations they directly interact with. It is for example relatively common (and sometimes even a legal requirement) to spay or neuter dogs. Spaying – removing the ovaries and uterus of a female animal – medical term = ovariohysterectomy. Neutering - removing the testes of a male animal – medical term = orchiectomy. Various humans activities (e.g. hunting, farming, fishing, industrialization, and urbanization) all impact various animal populations.

Population control may involve culling, translocation, or manipulation of the reproductive capability. The growth of a population may be limited by environmental factors such as food supply or predation. The main biotic factors that affect population growth include:

• Food – both the quantity and the quality of food are important. The population growth and decline of species depends on the amount of their food availability. The more available food, the more the population grows to meet it. The less food, the less fertile a species of reproductive age becomes.[1][2] Snails, for example, cannot reproduce successfully in an environment low in calcium, no matter how much food there is because they need this mineral for shell growth.
• Predators – as a prey population becomes larger, it becomes easier for predators to find prey. If the number of predators suddenly falls, the prey species might increase in number extremely quickly.
• Competitors – other organisms may require the same resources from the environment, and so reduce the growth of a population. For instance, all plants compete for light. Competition for territory and for mates can drastically reduce the growth of individual organisms.
• Parasites – These may cause disease, and slow down the growth and reproductive rate of organisms within a population.

Important abiotic factors affecting population growth include:

• Temperature – Higher temperatures speed up enzyme-catalyzed reactions and increase growth.
• Oxygen availability – affects the rate of energy production by respiration.
• Light availability – for photosynthesis. light may also control breeding cycles in animals and plants.
• Toxins and pollutants – tissue growth can be reduced by the presence of, for example, sulphur dioxide, and reproductive success may be affected by pollutants such as estrogen like substances.

Animal euthanasia is often used as a final resort to controlling animal populations. In Tangipahoa Parish, Louisiana, the parish performed mass euthanasia on the entire animal shelter population, including 54 cats and 118 dogs that were put to death due to a widespread disease outbreak that spread among the animals.[3]

Neutering is another option available to control animal populations. The annual Spay Day USA event was established by the Doris Day Animal League to promote the neutering of pets, especially those in animal shelters, so that the population remains controllable.[4]

Wildlife contraception is used to regulate populations of animals in the wild.[5]

Several efforts have been made to control the population of ticks, which act as vectors of a number of diseases and therefore pose a risk to humans.

• Animal trapping
• Hunting
• Malthusianism
• Overpopulation in wild animals
• Trap-neuter-return for feral cats
• Wildlife management

• "A chat with Tim Flannery, senior research scientist, on Population Control". Karina Kelly, Peter Kirkwood, Owen Craig. Archived from the original on 2010-01-13.