Territorial behavior is exhibited by nearly every type of animal, even humans. As with any competitive behavior, defending ground has benefits and costs. Possessing sufficient territory gives the holder access to forage areas, enhances the chances of attracting a mate, and reduces vulnerability to predators.
Defending Your Space
Territorial animals usually defend areas that contain, a nest, den, or mating site and/or sufficient food for themselves and their young. Conspecific (same species) conflicts usually involve ritualistic defense displays and bluffs and rarely take the form of actually fighting.
Defense threat displays may be visual as in the color of feathers or fur, auditory as in bird song or the howls of gibbons, or olfactory through the deposition of scent marks. Many territorial mammals use scent marking to signal the boundaries of their territories.
These marks by be deposited by rubbing parts of the body that contain special scent glands against some object, by defecation or deposition of strategically-placed urine. For example, canids such as dogs and wolves scent mark by urination and defecation, while felines such as house cat, lion, and tiger scent mark by rubbing their faces and flanks against objects.
The Cost of Holding Territory
The territory holder usually maintains ground only by expending much time and effort in its defense. Sunbirds, for example, can expend up to 3,000 calories per hour patrolling and defending territory. Such costs can only be paid and benefits realized if there is an abundance of food to support it.
If food supplies are low, an animal may not gain enough energy to balance the energy used in defense. In such circumstances, it is not advantageous to be territorial. If food supplies are high, an animal can meet its daily energy needs without the added cost of being territorial. From an energy standpoint, defending even abundant resources usually isn’t worth the cost. Thus, territoriality usually only occurs at intermediate levels of food availability, where the benefits of defense offset the costs.
The Size of Territories
Territories vary greatly in size and are usually related to the mating system of a species. A male song sparrow may have a territory of approximately three-fourths of an acre while birds that congregate in large colonies, such as gulls, gannets, boobies, and albatrosses, will precisely space their nests just beyond the pecking distance of the neighbors on all sides.
Territorial behavior is actually demonstrated by a minority of species and it is more common in birds than it is in mammals. Birds have less difficulty patrolling a large area for enemies and competitors than do mammals. For this reason, many mammals establish a home range. The area an individual or group covers or patrols in its normal routine constitutes its home range.
As the area covered is not exclusive to or solely defended by any one individual, a home range often overlaps the home ranges of others of the same species and individuals or groups do not usually defend their entire home range against other animals. Within the home range there may be a core area that no other individual or group use, but again this is usually as a result of avoidance rather than defense.
Sometimes the space defended moves with the individual. Known as individual distance, these traveling spaces can be observed in the spacing between birds on a wire or people waiting in line at the school cafeteria.
The vast majority of animals do not demonstrate territorial behavior but for those that do, defending their space is critical to the survival of the individual and to the reproductive success of the species.
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