Animals that live in the natural ecosystem requires the basic essentials in life such as food, water, shelter and housing. For each of the different types. If you have a population in excess of that environment will support. The number of animals is reduced by nature.
Animals in natural ecosystems like the basic necessities of life such as food, water, shelter and refuge for each species varies. If the population exceeds the capacity of the environment. Number of animals to fall naturally.
Animals in the natural ecosystem need necessary base in living, including food, water, housing and shelter, for each different type. If a population more than the environment supports.