Module 8 Lesson 4 - 1

Get Focused

At any given time, you can access information about populations of many species in our national parks. When we read about the numbers of individuals in a given population, we might have the impression that numbers are static. In fact, in an open environment, numbers change constantly; a population count signifies just a moment in time.

White-tailed deer enjoy the tender buds of shrubs and young trees that make up the transition area between fields and forest. Increasing deforestation due to urban sprawl and agriculture has opened much more of this transitional habitat. In addition, the same human activities have forced natural predators of deer such as coyotes from these areas. Hunting, which has been a traditional method of keeping white tail deer populations low, is out of favour in modern times. Current society depends largely on meat from domestic animals such as cows, pigs, and poultry.

With high food supply and without predators, the size of white-tailed deer populations is large enough that in many areas of North America white-tailed deer are considered pests. In the state of Pennsylvania, more deer are killed by cars on the highway than die as a result of hunting. An increasingly popular product is a device that sends out a high pitched sound from cars travelling rural roads, thus deterring deer from crossing roads and preventing vehicle-deer collisions.

Without competition and predation to remove the sick and poorly adapted, the gene pool of white-tailed deer is becoming weaker, expressed in a greater incidence of parasitism and contagious disease. With natality (birth rate) greater than mortality (death rate), the rate of growth continues to increase. With little selection of superior alleles, the gene pool increasingly is inferior to its previous generation.

By the end of this lesson, you should be able to respond to these four focusing questions:

• What factors influence population size?
• How do these factors influence population change?
• How can data be analyzed to study population dynamics?
• What terms describe these population changes?