Scientists of University of East Anglia have discovered that warblers on Cousin Island in the Seychelles believe in co-operative breeding . If the habitat depletes many birds prefer to be “helpers” than have their own offspring. In 1996 when excellent rains increased the food availability the Seychelles warbler prolonged their reproductive season making it year-round breeding.

After leaving his mother, an adolescent cougar or mountain lion wanders in search of its own territory. Only when he/she has its own home range will he/she be able to have exclusive control over territory and food supply. Until this point, there will be no mating. When there are too many adults for the prey base to support, cougars have smaller litters or skip a breeding cycle entirely.

Hunters argue that one of the reasons hunting of deer,elk,ibex is undertaken is to limit their population. Nothing can be further from the truth. John Fawcett, a Mammal Society deer specialist who has studied roe deer populations in the New Forest, said the deer numbers in the New Forest halved for the 20 years until 1992 inspite of no killing, simply because of the intrusions into the forest by humans

Aquatic animals exhibit self regulation in population as well. The effect of food availability on reproduction was investigated in the marbled salamander. The animals were divided into three groups. At the end of the experiment, 60% of the high-food females were reproductive. In the medium and low-food groups, these numbers were 42% and 12% respectively. These results demonstrate that food availability influences the population dynamics of a species. In the Calanus finmarchicus, a microscopic crustacean in the northern North Atlantic, when the nutrient pool decreases below a minimal critical value no eggs are laid. When food is reintroduced, growth starts again.