Population Size

Population Size

  The four factors that produce changes in population size (whether it be animal or human) would be birth rate, death rate, immigration, emigration.  The concept of birth rate refers to the number of live births per one thousand individuals in a year's time. This rate, however, can be affected by factors like (in the animal world) the availability of nutrition, fertility, the number of predators in the vicinity, and access to a protective habitat. For humans it would also include the availability of sustaining nutrition, a protective habitat, fertility rates, but added extras like abortion, the social value of the offspring, availability of contraceptives, and the culture in which one lives. Death rate refers to the number of deaths per 1000 individuals in a year. Death can occur because of crime, disease, war, corrupt rulers, accidents, starvation, natural disasters, and many other causes.  Of course the death rate can also be lowered through medical technology, improved health care, better nutrition, and people who care enough to help. Immigration is the number of individuals moving to another country, and. emigration is the number of individuals leaving that country. This again could be caused by war, discrimination, desire for a better life and freedom, and even natural disasters.

I believe the factors that affected population size in the video was high birth rate (they had plenty of food and a good habitat to live in), a low death rate (for the same reason), and no emigration. They do not need to leave the area right now.

Of course, once they have depleted all their resources, I believe that the nutria will simply move on to greener pastures.  This depletion could be stopped if PETA would let people trap them for their furs again; that would keep the numbers down and we could control the depletion.