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Living on the edge
by Ron Eakes, Wildlife Biologist


The first thing that comes to most people’s minds when they hear the phrase "living on the edge," is some kind of life in the fast lane, where danger or intrigue lie just around the next corner. However, when it comes to most species of wildlife, living on the edge is exactly what they do on a daily basis. In this case, the "edge" referred to is where two or more kinds of habitats come together.

Biologists often refer to these edge or transitional areas as ecotones. Several examples of edge would

be where a mixed hardwood forest meets an open pasture or a mature forest meets a thicket or a young forest.

The reason that edge is so important to wildlife is that most wildlife species depend on more than one habitat type to meet their basic needs of food, cover, water, and space. Food must be present throughout the entire year. Cover is needed for things such as resting, escaping predators, protection from bad weather and nesting or the rearing of young. Water doesn’t always have to be in the form of ponds, lakes or streams. Sometimes an animal can obtain moisture from the food that it eats or, in the case of some birds and small mammals, by drinking dewdrops. The amount of space needed varies widely from one species to the next.

In most cases, a single habitat type can meet one or possibly two of these requirements but usually not all of them. In some cases a particular habitat may meet certain requirements only during a particular time of year. For example, a mature oak forest may provide an abundance of acorns, an excellent food source for white-tailed deer during the fall, but little other food is available during the rest of the year. A large soybean field can seasonally provide an abundance of food; but often times, little cover is available in the center portions of the field which results in most species being unable to utilize that food.

Typically, as you increase the number of habitat types in a given area and the total amount of edge between them, you also see an increase in the total numbers of a particular species that can utilize the area. In addition, this change tends to also increase the total number of different species that the area can support. This phenomenon is commonly known as the "edge effect."

The edge effect is most pronounced in species that have small home ranges, such as bobwhite quail, rabbits and some species of songbirds. These animals typically have home ranges that cover only a few acres. Animals such as white-tailed deer, wild turkey and black bears require less edge per unit of area because of their larger home ranges. A large home range allows these animals to move greater distances to find the habitat types necessary to meet their basic biological needs.

Edge and the effects that it produces are important to anyone interested in managing for wildlife — from homeowners who are interested in creating a small backyard habitat for bird watching, to the avid hunter interested in improving his property or leased lands for white-tailed deer, turkey or quail.

Interspersion of different habitat types and the edges that they create are key to successfully establishing and maintaining healthy and abundant wildlife populations.

For more information on creating or enhancing wildlife habitats, please contact Ron Eakes, Wildlife Biologist, Wildlife and Freshwater Fisheries Division, 21438 Harris Station Road, Tanner, AL 35671.



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Date Last Updated January, 2006