Territoriality is a type of intraspecific or interspecific competition that results from the behavioral exclusion of others from a specific space that is defended as territory. This well-defined behavior is exhibited through songs and calls, intimidation behavior, attack and chase, and marking with scents. This form of defense proves to be very costly for animals. So one is forced to ask, Why do animals take part in such interspecific competition?
In order to understand this question one must take a cost-benefit approach to territoriality. The proximate reasons for such defense vary. For some animals the reason for participating in such elaborate protective behavior is to acquire and protect food sources, nesting sites, mating areas, or to simply attract a mate. The ultimate cause of this behavior may be attributed to the increased probability of survival and reproductive successes. In defending a territory an animal is ultimately securing that it will have an habitat in which to forage for food and to successfully reproduce, thus increasing the animal's overall fitness. This ultimate theory is strengthened when one considers the instances in which territoriality increases; in times of depleted resources the presence of territoriality increases. The presence of territoriality often forces less fit animals to live in sub optimal habitats, thus reducing their reproductive success.
Though territoriality offers immense reproductive and nutritional benefits, it also comes at a cost. Defending territory is not easy. Territoriality cost time and energy and can often interfere with other fundamental activities as parenting, feeding, courting, and mating. For these reasons territoriality may not be seen as a benefit in all animals. Animals must be able to reap the fruits of territoriality, while expending the least amount of energy. For these reasons if resources are abundant and predictable it would be disadvantageous to defend the territory. On the other hand, if resources are scarce and undependable it would be advantageous to exhibit territoriality.
An animal chooses its territory by deciding what part of its home range it would like to defend. In selecting a territory the size and the quality play a crucial role in determining an animal's habitat. Territory size generally tends to be no larger than the organism than requires to survive, because with an increase in territory comes an increase in energy expenditure. For some animals the territory size is not the most important aspect of territoriality, but rather the quality of defended territory. The quality is considered to be fundamentally important due to the amount of food availability and superior nesting sights. Animals depend on these features to ensure their superior fitness.
Animals invest much time and energy in defending their territories, and for this reason they fight vigorously to defend their territory at all cost. Researchers suggest for this reason that when a rival challenges a territory holder, the owner almost always wins the contest. This phenomenon could be attributed to an evolutionary stable strategy which assets that rules for behavior are controlled by an inherited proximate mechanism such that the differences between individuals in their strategies are liked to differences in their genes. Territory plays an important role as a mechanism of population regulation, insuring the success of fit animals, and aiding in the eradication of less fit animals. Territoriality also plays a fundamental role as an indicator of carrying capacity; it also serves as an indicator of how much habitat is necessary to support viable populations. For these reasons researchers continue to examine the well-developed behavior of territoriality.
Links to Territoriality
Territoriality and Property http://www.umass.edu/preferen/gintis/Evolution%20of%20Private%20Property.pdf
Interspecific Competition http://www.tiem.utk.edu/~gross/bioed/bealsmodules/competition.html
References Alcock, John. Animal Behavior: An Evolutionary Approach, Seventh Edition. Massachusetts: Sinauer Associates, Inc., 2001
SMITH ELEMENTS OF ECOLOGY (SET:TXT/ECOL ACT GDE) (P) Fifth Edition.