Stotting

A young springbok stotting

Stotting (also pronking or pronging) is a behavior of quadrupeds, particularly gazelles, in which they spring into the air, lifting all four feet off the ground simultaneously. Usually, the legs are held in a relatively stiff position and the back may be arched with the head pointing downward. Many explanations of stotting have been proposed; there is evidence that at least in some cases it is an honest signal to predators that the stotting animal is not worth pursuing.

Etymology

Stot is a common Scots and Geordie verb meaning "bounce" or "walk with a bounce." Uses in this sense include stotting a ball off a wall, and rain stotting off a pavement. Pronking comes from the Afrikaans verb pronk-, which means "show off" or "strut", and is a cognate of the English verb "prance".

Occurrence

Stotting occurs in several deer species of North America, including mule deer and pronghorn, Columbian black-tailed deer when a predator is particularly threatening, and in a variety of ungulate species from Africa, including Thomson's gazelle and springbok.

Stotting occurs in domesticated livestock such as sheep, but is typically performed only by young animals.

Possible explanations

Stotting makes a prey animal more visible and uses up energy and time that could be spent escaping. Therefore, it is assumed that it must bring some benefit to the animal performing the behavior. A number of possible explanations have been proposed for stotting. Stotting may be:

1. A good means of rapid escape or jumping over obstructions. However, this cannot be true in Thomson's gazelles because these prey animals do not stot when a predator is less than approximately 40 m away.
2. An anti-ambush behavior; animals living in tall grass may leap into the air to detect potential predators.
3. An alarm signal to other members of the herd that a predator is hazardously close thereby increasing the survival rate of the herd.
4. A socially cohesive behavior to escape predators by coordinated stotting, thereby making it more difficult for a predator to target any individual during an attack (much like the suggestion that zebra stripes cause motion dazzle).
5. An honest signal of the animal's fitness. Stotting could be a way of deterring pursuit by warning a predator of the animal's unsuitability as prey: the prey benefits by not being chased (because it is in fact very fit); the predator benefits by not wasting time chasing an animal it is unlikely to catch. This signalling theory explanation avoids the group selection connotations of the "alarm signal" and "socially cohesive" escape hypotheses.
6. An instance of Amotz Zahavi's handicap principle, whereby stotting is signalling to predators that the animal is so fit it can escape even if it deliberately slows itself down with some apparently useless behavior (i.e. stotting).
7. A predator detection signal whereby the animal signals to the predator that it has been seen and therefore does not have the advantage of surprise. Many such signals exist in different groups of animals. Again, this would be an honest pursuit deterrence signal, benefiting the prey by not being chased (because it can be seen to be aware of the predator and ready to escape immediately) and benefitting the predator by not wasting time stalking prey when it has already been seen. Evidence for this hypothesis is that cheetahs abandon more hunts when their gazelle prey stots, and when they do give chase to a stotting gazelle, they are far less likely to make a kill. However, gazelles stot less often to cheetahs (which stalk and would therefore probably give up when detected) than to African wild dogs, which "course" (chase prey relentlessly, not relying on surprise).
8. A fitness display to potential mates in a sexual selection process rather than an antipredator adaptation.
9. Play, especially in young animals, which may help to prepare them for adult life. In favor of this hypothesis, stotting is sometimes observed in immature animals, however against the play hypothesis is that stotting is "generally" seen in adult prey responding to predators.

The English evolutionary biologist John Maynard Smith concludes that "the natural explanation is that stotting is an index of condition and of escape capability", used as a signal especially to coursing predators. He also observes that "it is hard to see how it could be a handicap", unless perhaps it is a signal to other gazelles of the same species.

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  A lamb stotting

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  An adult male Black-faced Impala stotting in Namibia

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  A gazelle stotting

See also

• Aposematism
• Deimatic behaviour
• Signalling theory