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Zachary Cavas via Royal Society
This ground squirrel didn't make it. The tail of the prey hangs out of a rattlesnake's mouth.
When ground squirrels wave their tails back and forth, it's apparently meant to send a message to rattlesnakes not to mess around with them — and a newly published study suggests that the snakes are getting the message.
The "tail-flagging" study, appearing in the Proceedings of the Royal Society B, was aimed at understanding how predators and prey communicate with each other. Matthew Barbour, a biologist at the University of British Columbia, said previous studies have shown that the squirrels wave their tails when they're in the presence of snakes, their natural predators, but also when there are no snakes around. Does the tail-waving really make a difference?
"We wanted to see whether this behavior influences how the rattlesnakes hunt," Barbour told me.
So, Barbour and a colleague at San Diego State University, biology professor Rulon Clark, went out to a couple of field sites in California's Alameda County and collected 22 rattlesnakes. The researchers hooked up the rattlers with radio transmitters, then tracked them as they made their way through areas frequented by ground squirrels.
Barbour and Clark observed dozens of squirrel-snake encounters, involving 14 different snakes. One side of the experiment focused on the snakes. "Snakes only strike at squirrels that are tail-flagging if they get really close," Barbour said. If a tail-flagging squirrel is more than 20 centimeters (8 inches) away, a rattlesnake will hardly ever attack. Even when snakes decided to lunge at a tail-flagging squirrel at close range, all but one of the squirrels got away.
In contrast, Barbour said that "if the squirrel's not tail-flagging, snakes strike more than 90 percent of the time," even if that prey is at the very edge of the snake's strike range (31 centimeters, or 1 foot). Squirrels who didn't wave their tails survived a strike only about half the time (seven out of 13 strikes).
The other side of the experiment had to do with whether the squirrels tried dodging the snakes during an attack. In all five cases where squirrels waved their tails, they dodged. In comparison, the squirrels who didn't wave their tails dodged in only five of the 12 cases observed.
This video shows a non-tail-waving ground squirrel pup being bitten by a rattlesnake. The snake drags the squirrel into the burrow, releases it, and later emerges to look for the envenomated prey using chemosensory searching. Meanwhile, a tail-waving adult squirrel investigates.
"We essentially provided the first field evidence supporting the hypothesis that tail-flagging honestly advertises a squirrel's vigilance toward snakes," Barbour said.
Barbour said tail-flagging tells the snake that this particular squirrel is on guard and ready to dodge the blow. It also alerts other squirrels in the area that danger is near, further reducing the snake's chances of making a kill. That apparently persuades the snake to look elsewhere for its next meal — for instance, amid a gaggle of squirrel pups that haven't yet perfected their tail-wagging, snake-dodging tricks.
"Our study serves as a demonstration that a single anti-predator signal, even when displayed frequently in the absence of a predator, can still influence predator behavior through multiple mechanisms," Barbour and Clark write.
Barbour said the study could lead researchers to take a closer look at the evolutionary dynamics behind predator-prey signaling — not only squirrels vs. snakes, but also lizards vs. snakes or gazelles vs. cheetahs. Hey, maybe animals are smarter than we thought. But you knew that already, right?
More about squirrels and snakes:
- RoboSquirrel vs. rattlesnake: Who wins?
- California squirrels yank rattlesnakes' tails
- Sociable rattlesnakes cuddle with their kin
- Saber-toothed squirrel looked like 'Ice Age' cartoon
The researchers say that "all methods adhered to were approved by the Institutional Animal Care and Use Committee at San Diego State University." The research was funded by an Animal Behavior Society Student Research grant, American Museum of Natural History Theodore Roosevelt Grant and SDSU's Mabel Myers Memorial Scholarship, provided to Barbour; and grants from the National Geographic Society and the National Science Foundation, provided to Clark.
Alan Boyle is msnbc.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.
Leave a Comment:
If you ever go snake hunting ....
Do it in the morning when the snakes are cold or cool ....
They won't be as active or frisky then ....
Thanks Alan ....
Squirrels are cute, snakes stop hunting them!
Leave the snakes and the squirrels to themselves. If those people hunting squirrels think that something like a squirrel is that much of a problem, they need to move to a high-rise condo and get away from nature.
I would hope people have more productive things to do with their time then this nonsense. This is what parents are paying a fortune to send their kids to college for?
LB - then don't send your kids to college. They can then get used to hearing 'I'll have fries with that order, thanks'.
Its not always 'what' you learn but the methods and processes for solving problems, thinking critically and achieving results.
Could it also be that tail-waving is a common trait among squirrels that just happen to be more "twitchy" and agile than their more laid-back cousins?
Hi hawaiicharles,
The tail-waving behaviour is common amongst all ground squirrels and they display this behaviour both when they have seen a snake and when they are moving through areas in which they are likely to encounter a snake (e.g. squirrel burrow or tall grass).
What a WASTE of time and money. The study itself may have value long term if they had more numbers but they looked at 14 snakes and 12 squirrels? Or there about. Statistically speaking the sample is not large enough. Also as another poster noted time of day can have a lot to do with results. Was that factored in? How many events did they track or just one apiece per snake? Junk science at it's worst.
If you read more carefully, there were multiple observations for each snake. It is not easy to get this kind of footage on video. Requires a lot of work setting up remote cameras on rattlesnakes for days at a time, waiting waiting waiting. Really it is quite impressive that they were able to witness as many interactions as they did.
Hi Squam8,
Thanks for acknowledging all of the time and effort that went into this research.
Hi trust_verify,
Actually, statistically speaking, the sample was large enough to draw these conclusions, otherwise it would not have been published after going through peer-review. All of these interactions occurred during the day, when snakes were hunting ground squirrels, and their body temperature was sufficient to effectively strike squirrels.
i saw a chipmunk tail-flag at a mouse trap
So the moral of the story is.....? If you don't want to get hit on, shake your booty?
Could it also be that the moving tail confuses the snakes at bit and causes them to strike towards the tail more than the body of the squirrel? Even for reptiles, pit vipers are not known for their intelligence.
Hi Dale3242,
Good point. However, we also looked at that in our study and found that tail-flagging had no effect on snake strike accuracy.
I can agree with the article that the tail wagging is a sign that the squirrel is very attentive but since rattlers have very poor vision, I don't see where this would be a sign for the snake to know not to strike out past a certain range based on visual acuity. It is much more probable that the tail movement confuses the snake's ability to stike due to the radiated body heat in the tail moving back and forth so quickly taking attention away from the squirrels body. Rattlers strike mostly at heat movement and not much at visual movement. Their heat sensing ability is much better than their visual acuity. If the squirrel is very close, then the body heat of the squirrel's body will as detectable as the tail movement producing the a close in and fairly accurate strike. The farther away the squirrel is from the snake, the more confusing the heat signature because of the fast side to side movement of the tail will be to the snake, and this reduces the likelyhood of a strike that will cause the snake to extend out to its maximum strike range , which is normally slightly more than about 1/2 half its length from a coil. I live in western diamond rattlesnake country on a ranch and have had many encounters with these critters over the years, some as big as 6.5 ft long. It is very easy to move slowly and simply walk out of strike range, while moving fast will produce an almost immediate strike with a high probability of a bite due to the fast heat movement detected by the snake. It surprises me that this researcher does not seem to factor in the heat signature of the moving tail as a form of diversion such as the Air Force uses for defense against heat seeking missles.
Common sence and casual observation over time teaches us a lot- we just dont get paid as well to produce "scientific" evidence. What a waste of their time and our money.
W.C, Pit vipers, such as rattlesnakes, use their heat sensitive pits when hunting at night. At night the warm body of a mammal or bird stands out compared to the cooler background. I believe the researchers in this case observed the snakes during the day when body heat would be masked by other hot surfaces.
Pit vipers can strike up to 1/2 of their body length and will do so to defend themselves against large animals. However, when a snake is attempting to feed, it will rarely strike more than 1/4 of its length. Part of this is the need for accuracy and part is a certain level of caution to properly identify the potential prey.
Hi W.C.,
We looked for an effect of tail-flagging on snake strike accuracy and didn't find any effect. Snakes often missed tail-flagging squirrels because they dodged out of the way and not because their strike was inaccurate.
In the south everyone is afraid of any snakes and kill most of them so the squirrels don't have to wave their tails. No I haven't seen this behavior.
Wow! What an utter and complete waste of research grant money. Reminds me of the the study done on the barfing habits of the great horned owl.
Clearly, people who are funding these projects did not think this study was a waste of money. Every project you read about is in about the top 10% of applications, that go through rigorous review, by intelligent people. These studies have bigger implications than squirrels and rattlesnakes, if that wasn't interesting enough to you.
That depends upon the subject field. On the other hand, much medical research is a waste, apparently not subject to rigorous review.
Maybe it's a general sign of fitness, like the stotting of antelopes. Predators prefer to go after weaker prey, to minimize their energy expenditure and maximize their success rate, so it makes sense that they would avoid more difficult prospects.
To those who think this was a wasted study, why did you bother reading it? And then commenting on it? Don't you have anything better to do?
Hi rkaralius,
That's a good point, but I would argue that most of those fitness signals (or more formerly quality advertisement) are giving toward predators during a pursuit (like the stotting example you mentioned). I think tail-flagging is less energetically costly to the squirrels than stotting is to the antelopes so even squirrels of potentially lower fitness tail-flag.
Another STUPID Study! rkaralius!
Steve, why do you think we're here? To make more money? Get more stuff? No. We're here to learn. Anything that increases our understanding of the natural world we inhabit is worthwhile. And YES, I'm a working taxpayer.
my local squirrels exhibit this behavior all the time in my backyard and we have NO snakes....they shake their tails at each other and make a squirrel noise at the same time...I agree they are cute critters...snakes NOT so much....hate them!!
Queenie, I've noticed that too - they definitely use their tails as a means of communication. And umbrellas. :-)
Hi the queen,
Squirrels will often do this behaviour both in the presence and absence of snakes, which is why it was so interesting to find that it still influenced the snakes behaviour!
Did anybody ask the snake if he or she was hungry first?? Yeah forgot about that didn't you in your study.
Hi RyanDallasTexas,
We only included observations from snakes that had not eaten a squirrel in several days and were in an ambush position near squirrel burrows, so I think it is safe to assume these snakes were hungry and looking for a meal.
So if you're ever out hiking and encounter a snake, wag your butt.
The squirrel that is getting eaten by the snake probably read this article and just stood there waving his tail. Stoopid squirrel. I'm all for analytical knowledge, but these jerks just wasted somebody's money.
So if waving interesting information on front of humans produces a benefit (humans paying attention) the overall point should be that humans become more educated. So humans paying attention should be good positive outcome to engage in and humans benefit by being so engaged.
The creatures living in Mother Nature live within nature's limits, and as creature do not destroy Mother Nature herself. The fact that creatures live unassisted by artificial energy extracted from fossil fuels means that creatures are significant just for the fact that they live free and independent of artificial energy.
Humans are such slow and inattentive learners, it takes many, many examples, to illustrate the simplest point, such as the fact that animals adapt (wave tails) and show behaviors indicating that they have adapted (often wave tails), humans find this hard to understand.
If humans were threatened, by anything, they do not adapt, instead they would kill the living hell out of anything in the way, this becomes a habit and if you forgive a pun would easily kill the habitat they need to live in. Whereas the theoretical human could notice the waving or interesting information, become curious, investigate, document, confirm, verify and generally carryout activities that benefit human in another areas. Humans don't learn math to add two and two together, but math is useful is adding unknown x to unknown y and it is useful in thousands of new ways,
The subset of humans that use many, many examples, ascertain many facts and know the cost of obtaining that information across the animal kingdom, they believe this information and in the skills needed to capture this information and extract the truth are valuable exercises for both specific interest and general applicability (can read long sentences too).This becomes knowledge that may then be used to remind the ever lazy human who does not like to pay attention to survive, and to do so without investing in the effort independently.
The subset of humans that do not do anything of the above often consume information and benefit, but are unaware of how that information came to be known, to be transmitted from generation to generation or why it cost beneficial to not have to repeat the same experiment after the relationship was lost by not paying attention.
If you are smart enough you could hypotheses that two kinds of humans coexist, those that actively use their neocortex and those who don't. If we perform the tail waving experiment to gain the attention of those that use their neocortex then humans begin to accumulate knowledge etc. Those that do not respond to new information clearly have an unwanted dependency on other's use of their neocortex. Taken together these two kinds of humans exist, but advancements made by one group are offset by setbacks that are constantly introduced by the other group.
Humans are thus impaired in their advancement, making poor judgments, informed choices are forced to become guesses, and that which may be better is reduced to good enough and known good practice becomes random choice.
This is what meant by "reinventing the wheel", since doing so costs more and wastes time, in humans it has resulted in growth in science and technology, becoming vast capital enterprises, and extreme over use of energy and other resources. None of this exists in the natural world, to be noticed (wavy tail), and understood. Nature has already solved, many times over, the equation of life and evolutions and waves endless knowledge, in front of humans, saying "hello humans, I have a solution for you". Humans lacking a neocortex or outnumbered by those who don't have a neocortex, are the endangered species, if only because human technology is not tempered in wisdom, its stupendous success threatens the human habitat, and the human inhabitants refuse to use their peripheral vision to see, "wait a minute, this world got here long before the human experiment started."
The hundred million prognoses, suggests that humans are just another example of a failed experiment, and are not self-aware (a neocortex thing).
For the disinterested, become mute, and only use keyboards that are placed at least four feet in front of you.
Also get your tail in gear, and get moving, because that snake is going to bite you.