Deer need food and water to survive. what are food and water for the deer population?

The answer is limiting factors.

Limiting factors are factors that prevent a population from growing large. They limit the growth and distribution of organisms in the population. As the name says, they limit the population. For example, if there is not enough food and/or water, a deer will not survive. This will consequently affect the population size.

It is used to during sexual reproduction between humans