Territory (animal)
In ethology, territory is the sociographical area that an animal consistently defends against conspecific competition (or, occasionally, against animals of other species) using agonistic behaviors or (less commonly) real physical aggression. Animals that actively defend territories in this way are referred to as being territorial or displaying territorialism.
For other uses, see Territory (disambiguation).Territoriality is only shown by a minority of species. More commonly, an individual or a group of animals occupies an area that it habitually uses but does not necessarily defend; this is called its home range. The home ranges of different groups of animals often overlap, and in these overlap areas the groups tend to avoid each other rather than seeking to confront and expel each other. Within the home range there may be a core area that no other individual group uses, but, again, this is as a result of avoidance.
Function[edit]
The ultimate function of animals inhabiting and defending a territory is to increase the individual fitness or inclusive fitness of the animals expressing the behaviour. Fitness in this biological sense relates to the ability of an animal to survive and raise young. The proximate functions of territory defense vary. For some animals, the reason for such protective behaviour is to acquire and protect food sources, nesting sites, mating areas, or to attract a mate.
Among birds, territories have been classified as six types.[1]
Reports of territory size can be confused by a lack of distinction between home range and the defended territory. The size and shape of a territory can vary according to its purpose, season, the amount and quality of resources it contains, or the geography. The size is usually a compromise of resource needs, defense costs, predation pressure and reproductive needs.
Some species of squirrels may claim as much as 10 hectares (25 acres) of territory.[2]
For European badgers, a home range may be as small as 30 hectares (74 acres) in a good rural habitat, but as large as 300 hectares (740 acres) in a poor habitat. On average, a territory may be approximately 50 hectares (120 acres), with main setts normally at least 500 metres (1,600 ft) apart. In urban areas, territories can be as small as 5 hectares (12 acres), if they can obtain enough food from bird tables, food waste or artificial feeding in suburban gardens.[3] Spotted hyenas (Crocuta crocuta) have highly variable territory sizes, ranging from less than 4,000 hectares (9,900 acres) in the Ngorongoro Crater to over 100,000 hectares (250,000 acres) in the Kalahari.[4]
In birds, golden eagles (Aquila chrysaetos) have territories of 9,000 hectares (22,000 acres), least flycatchers' (Empidonax minimus) territories are about 600 square metres (6,500 sq ft) and gulls have territories of only a few square centimetres in the immediate vicinity of the nest.[5]
Territories can be linear. Sanderlings (Calidris alba) forage on beaches and sandflats. When on beaches, they feed either in flocks or individual territories of 10 to 120 metres of shoreline.[6]
The time to develop territories varies between animals. The marine iguana (Amblyrhynchus cristatus) is a lekking reptile. Males start to establish small display territories two months ahead of the mating season.[7]
Strategies[edit]
Animals may use several strategies to defend their territories.
The first game theory model of fighting is known as the hawk-dove game. This model pits a hawk strategy (always try to injure your opponent and only withdraw from the contest if an injury is received) against a dove strategy (always use a non-injurious display if the rival is another dove and always withdraw if the rival is a hawk).
Another strategy used in territory defence is the war of attrition. In this model of aggression, two contestants compete for a resource by persisting while constantly accumulating costs over the time that the contest lasts. Strategically, the game is an auction in which the prize goes to the player with the highest bid, and each player pays the loser's low bid.
Some animals use a strategy termed the dear enemy effect in which two neighbouring territorial animals become less aggressive toward one another once territorial borders are well-established and they are familiar to each other, but aggression toward unfamiliar animals remains unaffected.[41] The converse of this is the nasty neighbour effect in which a territory-holder shows heightened aggression toward neighbouring territory-holders but unaffected aggression to unfamiliar animals or distant territory-holders. These contrasting strategies depend on which intruder (familiar or unfamiliar) poses the greatest threat to the resident territory-holder.[42]
In territory defence by groups of animals, reciprocal altruism can operate whereby the cost to the benefactor in helping defend the territory is less than the gains to the beneficiary.
Polyterritoriality[edit]
Many species demonstrate polyterritoriality, referring to the act of claiming or defending more than one territory. In the European pied flycatcher (Ficedula hypoleuca), researchers assert that males exhibit polyterritoriality to deceive females of the species into entering into polygynous relationships. This hypothesis, named the deception hypothesis, claims that males have territories at distances sufficiently great that females are unable to discern already-mated males. The observation that males travelled long distances, ranging from 200m to 3.5 km, to find a second mate supports this argument.[54] The debate about polyterritoriality in this species may initiate research about the evolution and reasons for polyterritoriality in other unrelated species.