Biology is thin on the ground these past few weeks, so let’s look at a video of antelopes pronking. No, I didn’t say “bonking”! The behavior of this young Dama gazelle (Niger dama, a denizen of the Sahara and surrounding regions), is also called “stotting,” from the Scots word “stots,” apparently meaning to walk jauntily. When you see stotting in the video below, you’ll recognize it instantly if you have any familiarity with animal shows on television. The paper by Tim Caro at the bottom defines stotting as “vertical leaping with all four legs off the ground simultaneously, with the legs being held stiff and straight.” It also gives all the hypothesis for why stotting could have evolved (I list a few below).
Watch this three-week-old gazelle stot—and then rush about in normal running mode—at the Smithsonian (presumably the National Zoo in Washington, D.C. but perhaps at their reserve in Virginia):
Other quadrupeds do this, especially other species of gazelles. But what does it denote? We’re not sure. It seems maladaptive in an evolutionary sense, since it’s often done when fleeing from predators, and it’s not only inefficient, wasting energy when you could be running, but also makes you more visible. Yet, contra Larry Moran (who will probably weigh in here now!), I think the behavior is an adaptation. For one thing, many species show similar behavior under similar circumstances. But how could it benefit the genes that produce the behavior?
The Wikipedia article on stotting, and the two papers below, detail some of the theories and their tests. Here’s a short list:
- It allows an animal to jump out of high grass to look for predators
- The behavior startles the predator, giving the gazelle more time to escape
- It’s an alarm signal (like bird alarm calls), alerting herd members that a predator is nearby. This would probably evolve only if herd members were closely related, so the behavior could evolve via kin selection (assuming it’s individually maldaptive, which isn’t proven).
- It’s simply play behavior. But not only the young do it: adults pronk too when they’re chased by predators..
- It’s a way, in young gazelles, of letting the mother know the baby has been disturbed. This may be one function, but doesn’t explain stotting in adults.
- It confuses the predator. Presumably a herd of gazelle, all pronking, would puzzle a pursuing cheetah or wild dog, making it hard to pick out a given individual to chase. I don’t believe this for a second; predators aren’t that dumb, and in fact a predator would probably either learn to or evolve to concentrate on the stotting individuals because they might be easier to catch. (This “confusion” explanation was once used to explain zebra stripes: it might be hard to single out one zebra in a mass of fleeing stripey equids. But see my earlier post on another explanation for stripes.)
- It’s a way to attract mates, possibly by showing how fit you are. Sage grouse in the western U.S. form “leks” in which males group together and jump up and down for hours (making loud noises at the same time) while the females watch from nearby. Invariably it is the males who jump the longest that are chosen as mates. Females want a fit father for several reasons. This doesn’t wash for gazelles since both sexes do it, and not in a sexual context.
- This is a favored hypothesis: the “honest signal” theory. This posits that the behavior is saying to potential predators, “Don’t bother trying to catch me as I can bounce really high, so imagine how fast I could run if I wanted to!” In other words, the behavior deters the predator from attacking that individual.
- This is the hypothesis I find most credible: stotting warns the predator that it has been seen, thus discouraging it from pursuing the stotting animal. (Predators like to sneak up on a prey, getting as close as possible before they’re detected.) That is, stotting evolved via individual selection. Remember that predators often don’t go after a whole pack of quadrupeds at once, but single out certain individuals—often young or weak ones—to pursue.
Now all or some of these explanations might operate simultaneously, or they might all be wrong. The paper by FitGibbon and Fanshawe supports the last and the “confusion” hypotheses by showing that pursuing wild dogs were less likely to kill a gazelle when pursuing a pack in which more individuals stotted, and also that individuals who stotted for a longer proportion of the time during pursuit were less likely to be killed. But the data are scanty and the results barely significant in a statistical sense. (Of course it’s very hard to do this work in the field!) So, for right now, there’s no highly convincing explanation for stotting.
h/t: Matthew Cobb
_______________
Caro, T. M. (1986) The functions of stotting in Thomson’s gazelles: Some tests of the predictions. Animal Behaviour 34:663-684. (free download)
FitzGibbon, C. D., and Fanshawe, J. H., (1988), Stotting in Thomson’s gazelles: an honest signal of condition. Behavioral Ecology and Sociobiology, Volume 23, Number 2 / August, pages 69–74.
Great video. I used to run about like that as a child, it was fun, felt good, but I’m a bit heavier now. I thought it would just be sexy as adults, like dressing up or dancing, even sexier if done in front of a predator. But I’m just a physics student and that is my answer to everything I don’t understand, it’s sexy.
Why do human children (those little “wantons”) “skip” and run?
Seemingly because it’s so much “fun”?
Could it be so for a young gazelle
Who loves to “pronk” and run pell-mell?
Dogs love to play chase with their human companions. I’ve observed what surely seemed to be the black standard poodle equivalent of “pronking.”
Lambs are frequent stotters. The most sustained bouts of stotting amongst lambs which I have observed were on a Scottish island in an area well known for its growth of magic mushrooms. No scientific research was conducted: so just saying!
Did you eat the mushrooms with the lamb?!
Yes, but I never digested.
🙂
Amotz Zahavi calls this signal selection. (Steve Jones did some work for him I think, presumably as a graduate student.)
I think it is far too much of a melange to distinguish one of these from the others – it is like trying to separate the ingredients of a cake after it has been baked. However, I like the last two as they seem to me to be two sides of the same coin.
I have seen something very similar to pronking in young foals and colts. I always attributed it to playful behavior, but maybe it evolved for other reasons. I have not observed the behavior in adult horses, but that may be due to domestication and training.
As with deer they will look at potential predators though, won’t they, as if to say ‘I know you are there, just try it & I will run off & we both waste energy’?
I wonder – if we accept the last explanation, is stotting beneficial where animals are hunted by humans? Perhaps the invention of long range weapons is just too recent to have had an effect on gazelles & antelopes in particular, when they live near humans in Africa & Asia. (I know an early method of hunting would have been to use fire, or drive animals into corrals though). Perhaps they behave differently with humans?
Do they stott at night ‘for’ night time predators?
For a creature born with such *magnificent ability* to then grow up and wander a small enclosure and eat from a feeding station is a little sad. (Even if it’s saving the species.)
I believe it is called “gamboling” in lambs. I would have thought the extra muscular tension and rigidity were helping the juveniles to develop muscle tone and lose that floppiness of youngsters, but if adults do it in emergencies maybe it is just the consequence of overloading long limbs with muscular force.
Or, perhaps, quickly protecting their Achilles tendons and hamstrings? A predator who can snag either can slow and cripple his/her prey quickly.
In the U.S., stotting is typical of mule deer but isn’t usually seen in whitetail deer. The former inhabit grassland, desert, and open country; the latter prefer forest, chaparral, scrubby canyons, and plenty of cover. Where the two species are found together, as in much of the West, I suppose stotting could aid the deer in species recognition, especially when the tail “flag” isn’t visible.
Mule deer often inhabit the same areas as jackrabbits (which are hares, not bunnies). In watching both species running through grassland in Montana, Wyoming, and Arizona, I’ve noticed that in hilly country it can be difficult to tell whether the pair of ears bouncing away from me belongs to a bounding jackrabbit or a stotting mule deer! I’ve been fooled both ways. Might the “size confusion” hypothesis work this way too, saying not just “I’m bigger than you think”, but in some cases “I’m too small and fast to bother with”?
Perhaps that could be, with black & white visioned predators?
Maybe stotting in broken terrain would be more risky with the possible result of a broken leg. Also presumably those animals living in terrain with cover would use that cover rather than just pure speed to evade predators and stotting would be more likely to reveal their location.
Is it not the case that stotting is also quite common in pronghorn?
…who at one time had to avoid the Miracinonyx!
I’ve never seen it, but that doesn’t mean they never do it – maybe I never saw anything that would trigger that behavior. We lived in Cheyenne, WY for a year and a half, and did quite a bit of hiking etc. on the High Plains, and we saw antelope all the time (even a pair of them strolling on a downtown street!). They have little fear of humans and aren’t as wary as deer, perhaps because where they live, they can see anything coming for miles.
Dominic beat me to the comment – Miracinonyx, the Pleistocene giant cheetah, is long gone. Apparently the pronghorn has more staying power, and fossils of antelope-like creatures are known from the Oligocene, lying right under the feet of modern pronghorn herds.
Comment in favor of the honest signal hypothesis: Cheetas (and many other predators) are faster flat-out sprinters than Thompson’s gazelles (and other prey); the tommies escape by being able to zigzag and change direction faster.
It strikes me that pronking may be a way for a prey to signal to a predator not just general health, but specifically the agility needed to change direction mid-run. “I can make turns on a flipping dime. You can’t. You’re better off trying to eat Bob over there.”
Would be interesting to know exactly when a gazelle would stott when pursued by a fast predator such as a cheetah, compared to a slow one such as a lion. Perhaps they only do it when they know they have a speed advantage, or in the case of fast predators when they have evaded the predator and don’t need the speed? Do gazelle’s have the intelligence to differentiate between different predator types? – my guess is they probably do.
To continue the above – one might expect a gazelle not to stot when pursued by a pack of hunting dogs, since any loss of stamina would make the gazelle more likely to be caught, by the dogs whose strategy is to wear out their prey.
Multiple comments on the similarity with human young, but no suggestions on whether or not the similarity is superficial or how we’d know…any biologists able to offer any insight…?
b&
I suppose that play has an obvious role for the young of carnivores, but it doesn’t seem so clear why herbivores also play.
Establishing pecking order, exercise… inter alia?
Explaining the evolutionary role of play as exercise would seem a bit similar to explaining the role of sleep as being because animals get tired :). i.e. it rather begs the question.
Sorry — I didn’t mean play in general, but rather the specific form of play of bouncing up and down.
Human children especially get a kick out of using springs (beds / pogo sticks / etc.) when engaging in this form of play, but they’ll cheerfully do it without any mechanical aids as well.
b&
It means to show off in Afrikaans, as in the expression: “Hoe kaler jonker, hoe groter pronker”, ie the less he has(/the more naked), the more he boasts. It looks like fun.
What a fun contribution!
Kind of like “prance” in English…
Cognate.
On the other kilt …
… the Scottish-english word “stotious” does not mean “walk jauntily”, it means “to be thoroughly drunk”. It’s one of the many Scottish words expressing the same concept. There may be as many Scots words for differing degrees of drunkenness as there are Eskimo words for snow.
Is it more inefficient? Has anyone actually put this to the test?
When I look at that young gazelle stotting, it seems to me that it is engaging the large muscles less and relying on the spring action of its ankles and legs to move, kinda like an advanced athletic prosthesis. It is clear it can’t go as fast stotting as it can running, but it might be more energy-efficient to stot.
If so, it might be an energy conservation tactic. A gazelle stotting puts some distance between itself and predator and lets the predator know it’s been seen, while expending less energy than running. And if it turns out it really does have to run for its life, it has more energy to spare.
Isn’t the behavior probably driven by a combination of the possible benefits listed? I mean, an antelope didn’t wake up one day and say, “Hey guys, I think I have a solution to our Cheetah problem…” Isn’t that the beauty of a non-teleological process – the antelope can out-smart the predators (and biologists) without being all that smart?
la gacela puede saltar 2 metros de altura, la impala 5 y el antilope saltador 13 metros
13 metros de altura is not really plausible.
No highly convincing explanation? Well, honest advertisement seems pretty convincing to behavioral ecologists. The other hypotheses have been falsified (at least in the case of Thomson’s gazelle). Why should we care what Larry Moran (or PZ Myers, for that matter) thinks? Are they experts in the field of animal behavior?
Anyone’s allowed to think. And the guys with lots of letters after their names aren’t always the ones who make the discoveries in science.
Argumentum ab populum is a logical fallacy even if used by “behavioral ecologists”.
There comes a point, though, where popular opinion becomes scientific consensus.
Not that there’s no room for change at that point, of course, but one should expect something quite meaty to propel a change — and a corresponding shift in consensus.
Of course, that applies only to peer-reviewed disciplines with rigorous standards that fully embrace empiricism. Consensus amongst theologians means precisely dick, for example.
b&
What logical fallacy? The hypotheses have been tested and the evidence supports honest advertisement. Check the original papers or Alcock’s “Animal behavior”.
Another wild guess: it looks to me that an antelope running over terrain with lots of bumps or holes would be more stabile and less apt to trip or break a leg using the pronking method. So if I were an antelope on the run and encountered a rough patch I might choose to pronk over it. However, only a very light, long-legged creature could maintain any speed with this method.
Natural selection is a curious mix of adaptation and survival that is difficult to untangle with our frontal lobes that long for a good “just so” tale. Nonetheless, it is fun to try and account for why these seemingly maladaptive traits have persisted. What is missing is the realization that antelope (or antelope genes) not only compete against the cheetah, but also, and perhaps more doggedly, against other antelope. From an adaptive gene’s perspective too many antelope is as bad as too few. In other words, resource scarcity is likely to be a greater cause of mortality than predation. If a recessive gene caused an antelope (with two copies of the gene)to stot and reveal itself, sparing the rest of those with only one silent copy, then the allele might be an adaptive allele if the full expression of the behavior were not adaptive. So long as more survived in populations with the allele than in those without, the allele would be widespread even if it was maladaptive in its full expression. This has the added advantage of keeping herd numbers in check. Thus a “bad” gene is not always maladaptive.
Think there’s a group selection argument hiding somewhere here. If the double recessive was a disadvantage then any individual with the stotting gene would on average have less surviving offspring than individuals without it (since some offspring would be double recessive).
Nevertheless that’s precisely why the sickle cell gene persists where malaria is common.
In the case of sickle cell, the dominant trait has a phenotypic effect that causes a change in shape of red blood cells and makes them more resistant to the malarial parasite. That then makes up for the negative effect of the double recessive in malarial areas, so the gene was not selected against.
Maybe I didn’t understand Sciencem’s argument, but it seems to be suggesting that somehow the antelopes get an advantage from a stotting gene even though the dominant trait is neutral (does nothing). But in that circumstance, an individual *without* the gene would have an advantage (more surviving offspring), and that it doesn’t matter what would be better for the group as a whole.
Of course another weakness of the argument is that there is no suggestion that stotting actually is a double recessive, particularly as (I think) most/all individuals in a stotting species do it.
I see what you’re saying. I really hadn’t read sciencemd68’s post closely enough; jumped to a conclusion about what I thought it was going to say vs. what it actually says.
This was V. C. Wynne-Edwards’ group selection hypothesis back in 1962 in his book Animal Dispersion in Relation to Social Behavior. G. C. Williams thoroughly dismantled this hypothesis in 1966 in Adaptation and Natural Selection: A Critique of Some Current Evolutionary Thought. More recent theories of group selection (such as those proposed by George Price in and championed by D. S. Wilson and E. O. Wilson) do not use the same argument and are isomorphic with kin selection theory, as pointed out by W. D. Hamilton in 1974.
My long-haired Manx female confronts stray cats and the occasional dog by turning sideways with hair bristled [normal!], then closes by high stiff four-legged hops, still sideways, covering about 18 inches with each hop. Not sure if you could call it stotting, but as intimidation it works.
FWIW, as kids in Glasgow we would “stot” tennis balls off a nearby wall (cf. Steve McQueen in “The Great Escape”). I would therefore translate as “bounce”
While I think that the “honest signal” hypothesis is the most plausible in the case of gazelles, dismissing the play hypothesis because only juveniles play is based on false premises. Adults of many species (keas, ravens, humans, bottlenose dolphins, elephants, even Komodo Dragons!)often exhibit play behaviour so I see no reason why play should be dismissed as a reason for unusual behaviour in adults because clearly, play is not strictly the domain of juveniles.
Could it be a form of limbering up? Tennis players, sprinters etc do something similar when they’re getting ready.
I was going to say “working out” of a sort.
My hypothesis is that the same gene(s) that give an antelope or gazelle a tendency to change directions left or right when running (which give it a survival advantage over less agile predators) also cause the animal to want to stot. So the stotting behavior has no functionality in itself, it’s just part of the effect of genes that change the running style in another way that does serve a function.
It says, “I’m super strong and super fast. Eat someone else. Go fuck yourself.”
I looked at the etymology, since “stöt” means roughly ‘jounce’ in swedish. “Stot” came back as “To bounce, rebound or ricochet.” http://www.allwords.com/word-stot.html
Stotting was in common usage when I was young. It’s pronounced ‘stoating’ (as in boating) in scots. Stoating a ball was bouncing a ball. ‘Stoating’ also meant drunk. Presumably something to do with irregular sideways movements.
I like the hypothesis that the predators are too busy laughing to remember that they’re actually hungry.
Oh, that was excellent, Diane!!!
Here are a few things that could contribute to making pronking adaptive:
– If pronking let the antelope cover more ground in fewer steps, it would reduce the chances of the antelope stepping in a meerkat hole or something. Of course, if landing from a pronk is dangerous, this tradeoff might not be worth it.
– Pronking makes it difficult for the predator to get information about the upcoming terrain from be behavior of the antelope. The predator can’t know whether the antelope is a leaping over an obstacle or just pronking.
– It’s got to be more difficult for a predator to bite an antelope which is way up in the air; it would be really frustrating to make that final lunge and find that the antelope is suddenly above you. Does the rate of pronking change based on the distance between the antelope and the predator?
None of those are “explanations”, obviously, just things that might add a tiny bit of selective pressure.
You got me to wondering: What if pronking allows the pronker to offensively attack its predator from above?