thumb|Flight initiation distance (FID) buffer from critical wildlife area.
The flight zone of an animal is the perimeter area surrounding it that, if encroached upon by a potential predator or threat (including approaching humans), will cause alarm and escape behavior. The flight zone is determined by the animal's flight distance, sometimes also called flight initiation distance (FID) which extends horizontally from the animal and sometimes vertically. It may also be termed escape distance, alert distance, flush distance, and escape flight distance.
Swiss zoologist Heini Hediger distinguished between flight distance (escape 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).
Flight distance can be used as a measure of the willingness of an animal to take risks. Escape theory predicts that the probability of fleeing and flight distance increases as perceived predation risk increases and decreases as escape cost increases. Flight initiation distance is one measure of animals' fear responses to humans. Urban wildlifes, domesticated and captive animals, which are more accustomed to the presence of humans, have significantly shorter flight distances than wild animals.
In a study comparing 56 bird species with long flight distances, it was found these had declining populations in 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. This indicates animals sometimes maintain a flight zone around unfamiliar inanimate objects.
The flight initiation distance is being used as a tool in wildlife management. By studying flight zones, wildlife managers are able to reduce the impact of humans by creating ecological buffer zones between human settlements and animal habitats. These measures are usually used to quantify the tolerance of wildlife to humans.
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.
- 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.
- Social: In lizards, FID was shorter during social encounters than when they were solitary.
- 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. 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.
These measures are also important in birding and nature photography.
The FID in multiple species differs from rural to urban areas. A study by Møller et al. examined 811 FIDs from 37 species of birds and determined that the FID of birds in urban areas is reduced, compared to the FID of birds in rural areas. This may be due to a number of factors differing in rural vs urban areas, such as; difference in predator communities, length of exposure time to humans, relative abundance of humans, and the presence/abundance of food (bird-feeders in winter for example).
Some physical characteristics are very important to determine an animal's FID. Eye size and brain size have a role in determining the FID. A Cumulative Flight Zone is formed when animals move in a herd. In this situation the lead animal's and the following animals' Points of Balance, within the cumulative flight zone, must both be crossed to entice movement. Brahman cattle have a larger flight zone than most English breeds. The flight zone can be thought of as the animal's personal space. The size of the flight zone is determined by the tameness of the animal; the more domesticated an animal, the smaller the zone. Fully tame animals have no flight zone.
The flight zones in cattle vary depending on the situation they are experiencing. Novel situations increase their flight zone, while accustomed stimuli will decrease their flight zone.
Handlers sometimes make the mistake of deeply invading the flight zone when animals are being driven down an alley or into an enclosed area such as a crowd pen. If the handler deeply penetrates the flight zone, the animals may turn back and run over them in an attempt to escape. Confining a livestock animal in a crush (chute) or alley can make it feel more secure and thus reduce the size of the flight zone; however, it does not eliminate the flight zone. An animal in a livestock raceway or alley that feels threatened may panic and injure itself or other animals. If handlers lean over fences around animals they penetrate the "zone of safety" and may cause the animals to rear.
Husbandry
Animals have a tendency to move in the opposite direction when their handler walks deep into their flight zone. By crossing an animal's point of balance, within the flight zone, a handler can move the herd in a particular direction and control their speed of movement. For example, crossing the point of balance from front to back will move the animal forwards, while the opposite is also true. The handler's pace should always reflect the animal's speed when herding. Additionally, pressure should be alternated on the flight zone to reduce stress. When yarded, animals should always have room to turn away from the handler to reduce stress. Minimal stress prevents injury to the animal and maintains good production, such as increased quality of meat and improved muscle and fat scores. Epinephrine is commonly known as adrenaline. Adrenaline increases the supply of oxygen to vital organs and decreases supply to others. Frequent subjection to fight or flight situations causes severe endocrine disorders.
- The second phase is Adaptation and Resistance. It is the idea that recurring subjection builds natural immunity,
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| Eurasian blackbird ||align=right| 10 ||
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| Blue tit ||align=right| 10 ||
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Birds of North America
{| class="wikitable"
|-
! Species !! FID <nowiki>[</nowiki>m<nowiki>]</nowiki>
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| Golden eagle ||align=center| 105–390
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| Rough-legged hawk ||align=center| 53–884
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| Bald eagle ||align=center| 50–884
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| American golden plover ||align=center| 201
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| Great blue heron ||align=center| 201
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| Merlin ||align=center| 18–183
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| Prairie falcon ||align=center| 18–183
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| Great egret ||align=center| 101
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| Western Meadowlark ||align=center| 30
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| American robin ||align=center| 9
|}
Mammals of North America
{| class="wikitable"
|-
! Species !! FID <nowiki>[</nowiki>m<nowiki>]</nowiki>
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| Pronghorn Antilocapra americana ||align=center| 235
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| Mule deer Odocoileus hemionus ||align=center| 149–250
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| Elk Cervus canadensis ||align=center| 85–201
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| Bison Bison bison ||align=center| 101
|}
Factors affecting escape distances for birds
thumb|Fleeing [[Turdus merula|blackbird]]
Escape distance may differ significantly depending on many circumstances. Body size is the best known general factor influencing interspecies differences. Very frequently large species are more timid than small species, because size affects how rapidly a bird can take off. Surprisingly, an analysis of hundreds of studies found that larger birds are more tolerant of humans, despite substantial research that shows larger animals are less tolerant of humans.