The four factors that affect population size include:
Birth rate: The numberof births of a sample size (per1000 people per year). Birth rates are affected by many factors such as, the ability to receive health care, family planning, the use of availability of contraceptives, governmental policies, economic growth, education, social and cultural views, and the use of abortion.
Death rate: The number of deaths of a sample (per 1000 people a year). Death rates are caused by the lack of availability of food and water, lack of education, disease, lack of medical care, suicide, car accidents, crime, war, and government entities.
Immigration – People entering a country for various reasons.
Pull Factors – A country offering incentives for immigration, education, social and economic factors.
Emigration – People leaving a country for various reasons.
Push Factors - Social and economic factors, natural hazard, education opportunities, political instability, war, and others.
The factors that affect the population size in the video are birth rate and death rate. The female Nutria has the ability to give birth to up to 40 young in three years, with the young having the ability to reproduce at six months in age. This would give them the ability to flourish and build a very big population. The death rate would be regards to the vegetation population that the Nutria use as a food source. The Nutria have the capacity, and are, jeopardizing the vegetation in the swamp lands.
When the food source is depleted it can be expected to see the population decline due to death. Though, they may be able to adapt, or evolve, to the change and look to other food sources for survival.