Competition

Know this topic well? Help others and get FREE products!

Populations of animals are controlled by many factors. Natural selection is a broad term that describes one effect of these controls on population. For example, one form of population control that can result in natural selection is competition.

There are a number of essential resources upon which animals' lives depend. Whenever these resources are limited, animals are forced to compete for survival. Competition can be intraspecific, between the same species, or interspecific, between different species. Since resources are rarely abundant in any given environment, competition can be fierce. Three resources that animals are likely to complete for are space, water, and food.

The availability of space is a primary consideration in any habitat. The actual territory in which an animal lives is vitally important since an animal's environment must be able to support the needs of each species. All animals must have enough room for feeding, reproducing, and exercise in order to live comfortably.

Along with the amount of space, some animals require a particular terrain, such as the prairie dog. A prairie dog colony must have enough flat and fairly soft earth in which the animals can build elaborate tunnel systems. If the soil is too rocky, the prairie dogs cannot build their brooding dens and escape tunnels.

Similarly, some birds require lots of open sky in which to perform their courtship flights. Without these elaborate flights the birds do not become stimulated to reproduce. If the terrain does not permit the birds to move in wide-open spaces, the birds' chances of successful reproduction in that habitat are reduced.

Another important resource that animals compete for is access to water. Most animals require a particular amount of water everyday, which they may use as drinking water, or to contribute to their overall health. In general, animals must maintain a certain moisture balance in order for their tissues to work properly. When animals do not have enough to drink their bodily tissues become dehydrated and cannot function properly. Organs, such as kidneys, stop working, resulting in death.

Using larger bodies of water for bathing purposes is another common use of water as a resource. For instance, overheating in elephants is a problem usually countered by cool baths in rivers or mud. When water becomes scarce in the dry season, competition between individual elephants or between elephants and other species can reach a dangerous peak.

Finally, aquatic animals are especially vulnerable when the water level of their environment drops. Fish living in the shrinking rivers and streams are easy prey for birds when the waters become so shallow that they are easily seen. The fish will compete for choice hiding spots from hungry predators, with the unlucky losers being eaten, therefore removing their genetic material from the gene pool.

Food is one of the most basic resources over which individuals compete. In extreme cases where animals have gone for long periods without enough food to sustain them, individuals will compete, sometimes to the death, for mere scraps of food. Animals that practice a high level of parental care have to carefully balance finding enough food for both themselves and their offspring. When food is scarce, the parent may go for months without eating but will rarely risk their own death for the sake of their young. Usually, by the time the parent is in danger of starvation the resources for the young will have already been exhausted and the young will have already died.

The reason the parent allows its young to die is motivated by the parent's instinct to survive. Once the offspring dies the parent is free to read-opt food-finding methods that might lead it farther from the nest or den where its young were kept. The parent is driven to preserve its genetic information by remaining healthy enough so that it can reproduce again, hopefully when there is more food available.

Sometimes species will compete for more than one resource at a time. Competitions for territory and food are easily seen in interactions between ants. On one hand, the social structure of the colony is an amazing example of how the members of a species cooperate and specialize for the benefit of all. The queen lays the eggs and produces the offspring. Workers attend to the maintenance and growth of the colony. Soldier ants defend the colony against invaders. The area around an ant colony, however, is often lacking in food after a few seasons of food gathering and resource use.

Some colony members will forage beyond their usual boundaries and encounter ants from another colony. This will immediately set off a warning throughout both colonies. Soldiers and workers rush out of the twocolonies to fight each other for the contested territory and food resources. The success of one or both of the colonies may be at risk, and the death toll for each colony can be high. Even colonies of the same species will war against one another. If one species enters the colony area of another, the two colonies may suffer serious battle losses.

Although competition between animals can be seen in a variety of situations, many species have developed elaborate strategies to avoid competition. It is not the habit of any species to try and obliterate another. Confrontations occur as a last resort. Without this avoidance of direct competition there would be very few stable communities.

More often, the sharing of resources is achieved between species in a habitat. Scientists often refer to the sharing of resources as " niche partitioning." In niche partitioning animals tend to use different parts of a resource without coming into direct competition with one another. For instance, grazing animals in parts of Africa come in all sizes. The smaller Thompson's gazelles eat grass that grows close to the ground. Zebras and wildebeests consume the tall grasses and shrub food. The giraffe has a long neck enabling it to browse far above the ground. While all of these animals use plants as a food resource, none come into direct competition with one another. As a result, they coexist peacefully and reduce confrontation.

Many species of birds and monkeys in rain forests also partition resources. Some are specialized for feeding on fruit from lower branches of trees nearer the forest floor, while others are able to exploit food items found in the top or canopy region of the forest.

It is only when resources are limited that one observes any actual competition. Even then animals will often find a unique solution to the problem. For example, barnacle colonies exist in competition with other animals for limited space on rocks and hard surfaces in the oceans. While the larvaeare free-swimming and float as part of the planktonic community throughout their juvenile stage, the adults need a firm surface to anchor and construct hard permanent shells. From within these shells they extend feathery feeding appendages that sweep food particles from the ocean currents.

Barnacles exploit unique measures in order to avoid the fierce competition from ocean-dwelling filter feeders (such as corals, anemones, and limpets) for ocean floor space. Instead of competing, many form colonies on the tough skins of whales. They hitchhike around the sea feeding on food suspended in the water surrounding the whale. It is very common to find whales with large colonies of barnacles on their snouts and jaws. Even ships are suitable landing places for the barnacle larvae. Barnacle colonies can become so large on the bottoms of ships that the ships must be removed from the water and the barnacles scraped off to keep the ship moving smoothly through the water.

Ecological competition is a fascinating and varied topic in biology. Scientists are always discovering new ways in which animals compete with one another. Even more interesting is the way in which they reduce or eliminate competition. Humans can learn a great deal from how animals coexist with one another.

Examples of competition for water can be found in many nature videos. Parched elephants threaten thirsty lions for limited water in rivers. Baby elephants may get trampled in the rush for water and space in the limited water pools. Even crocodiles find competition as they march to a new water hole only to find resistance from crocodiles already in residence.

Aggression; Populations.

Raven, P., and G. Johnson. William C. Brown. Boston: McGraw-Hill, 1999.

Starr, C. Biology: Concepts and Application. Belmont, CA: Wadsworth, 1994.

University of South Carolina, Department of Biology. <http://marine.geol.sc.edu/BIOL/ Courses/BIOL>.

University of Tennessee, The Institute for Environmental Modeling. <http://ecology.tiem.utk.edu� 03e;.

University of Texas, Department of Biology. <http://www.esbutexas.edu> ;.

This is the complete article, containing 1,443 words (approx. 5 pages at 300 words per page).