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The flight zone of an animal is the area surrounding an animal that if encroached upon by a potential predator or threat, including humans, will cause alarm and escape behavior; the flight zone is determined by the animal's flight distance (sometimes called ''flight initiation distance'' (FID)) which extends horizontally from the animal and sometimes vertically. Swiss zoologist Heini Hediger distinguished between ''flight distance'' (run boundary), ''critical distance'' (attack boundary), ''personal distance'' (distance separating members of non-contact species, as a pair of swans), and ''social distance'' (intraspecies communication distance). Terms with similar concepts include ''escape distance'' and ''alert distance''. Flight distance can be used as a measure of the willingness of an animal to take risks.〔Moller, A.P., (2008). Flight distance and population trends in European breeding birds. Behavioral Ecology, 19: 1095-1102〕 Escape theory predicts that the probability of fleeing and flight distance increase as predation risk increases and decrease as escape cost increases. In a study comparing 56 bird species with long flight distances, it was found these had declining populations Europe. This indicates that standardized measures of flight distance can provide reliable information about the population consequences of risk-taking behaviour by individuals and the susceptibility of different species to increased levels of disturbance by humans.〔 When the flight zone of a group of bulls was invaded by a mechanical trolley, the bulls moved away and maintained a constant distance between themselves and the trolley.〔Kilgour, R., (1971). Animal handling in works, pertinent behaviour studies. 13th Meat Industry Research Conference, Hamilton, New Zealand. pp. 9-12〕 This indicates animals sometimes maintain a flight zone around inanimate objects. ==Factors influencing size== Animals faced with approaching predators must decide at which distance to initiate their flight, and they are expected to do so in a way that maximizes their fitness. As flight has both costs (including lost opportunity) and benefits, there will be in general an optimal flight initiation distance, defined as the first point in a predator's approach at which the benefit of flight exceeds the cost. The benefit of flight is equivalent to the cost of remaining in place or, in other words, to the risk of capture. The size of the flight zone can therefore vary according to circumstances. However, it has been shown in burrowing owls that individuals showed high repeatability in their FID.〔Carrete, M. and Tella, J.L. (2009). Individual consistency in flight initiation distances in burrowing owls: a new hypothesis on disturbance-induced habitat selection. Biology Letters, 6: 167-170 doi: 10.1098/rsbl.2009.0739〕 *Behaviour of the threat: In horned lizards, FID decreased as the distance between a turning predator and prey increased, but was greater when the predator turned toward than away from the fleeing animal. The FID and alert response of American robins to approaching humans was investigated; the greatest FID was when the approaching person was not on paths and was looking at the birds, while the lowest FID occurred when the person was on a path and not looking at the robins. The authors suggested this indicated that they use gaze direction to assess risk.〔Eason, P.K., Sherman, P.T, Rankin, O. and Coleman, B., (2006). Factors affecting flight initiation distance in American robin. The Journal of Wildlife Management, 70: 1796–1800〕 *Social: In lizards, FID was shorter during social encounters than when they were solitary.〔 and FID was shorter in female lizards when they were interacting with males than when they were alone; it was also shorter in males interacting with either sex.〔Cooper, W.E., (2009). Flight initiation distance decreases during social activity in lizards (Sceloporus virgatus). Behavioral Ecology and Sociobiology, 63: 1765-1771〕 *Distance to refuge: Gray squirrels (Sciurus carolinensis) typically run to the nearest tree to escape from predators. As the risk of capture increases with distance from the refuge tree, squirrels feeding far from trees should have greater FID than those feeding closer by. Confirming this, FID in response to a motorized model predator (a cat) increased as distance to refuge increased.〔Dill, L.M. and Houtman, R., (1989). The influence of distance to refuge on flight initiation distance in the gray squirrel (Sciurus carolinensis). Canadian Journal of Zoology, 67: 233-235 ()〕 Burrowing Owls breeding in territories far from roads showed larger FIDs than individuals breeding closer to roads and mated owls showed similar FIDs. Individual owls showed high repeatability in their FID.〔 *Training and learning: The size of the flight zone can depend upon the tameness or level of habituation of the animal. Completely tame animals have no flight zone for humans; that is, they will allow a person to approach and touch them. Wild, feral, and unbroken animals can have very large flight zones. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「flight zone」の詳細全文を読む スポンサード リンク
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