Defensive use of the tail in monitors – and also sauropods?

February 22, 2015

Murphy and Mitchell (1974: fig. 1)

Murphy and Mitchell (1974: fig. 1)

One thing that I’ve never understood is why some people are skeptical about sauropods using their tails defensively, when lizards do this all the time. I’ve been digging through the literature on this for a current project, and there are some really great accounts out there, and by ‘great’ I mean ‘scary’.

Here’s a key passage from Murphy and Mitchell (1974: p. 95):

V. salvator uses the tail to strike repeatedly in combination with biting for defense…Captive Varanus (varius, spenceri, mertensi, and salvadorii) use the tail for defense, but only salvadorii appears to aim directly for a handler’s eye. An adult male V. salvadorii accurately struck the senior author’s eye with the tip of the tail as he was attempting to maneuver the lizard. On many subsequent occasions, the monitor tried to strike the eye of the handler with accuracy.

Not being a monitor expert, I was initially thrown by the V. salvator/V. salvadorii issue. V. salvator is the water monitor, V. salvadorii is the crocodile monitor. Both get pretty darned big; Wikipedia lists 3.21 m (10.5 ft) for V. salvator and 2.44-3.23 m (8.0-10.6 ft) for V. salvadorii.

Anyway, I’d heard of lots of anecdotal reports of lizards from many clades using their tails to lash at rivals, predators, or handlers, but I’d never read about a lizard aiming directly for the target’s eyes. It immediately made me think about (1) sauropod tails, especially the whip-lash tails of flagellicaudan diplodocoids and at least some titanosaurs (Wilson et al. 1999), and (2) the supraorbital crests and ridges in many theropods, especially big Morrison forms like Allosaurus and Ceratosaurus. Of course, supraorbital crests in theropods could serve many functions, including shading the eyes and social and sexual display, but it’s interesting to speculate that they might have had a defensive function as well. Has anyone ever proposed that in print?

Diplodocus USNM 10865 - Gilmore 1932 pl 6 - cleaned up

Diplodocus longus USNM 10865, from Gilmore (1932: plate 6)


Most of the papers that pooh-pooh the use of whiplash tails in defense (e.g., Myhrvold and Currie 1997) argue that the tail-tip would be too small to do any serious damage to a multi-ton attacker, and too fragile to survive an impact. This seems wrong-headed to me, like arguing that unless you find putative animal weapons broken and caked in their adversaries’ blood, they aren’t used as weapons. A structure doesn’t have to do lethal damage or any damage at all to serve as a weapon, as long as it dissuades a predator from attacking. I’d think that getting hit in the eye by a 35-foot bullwhip might convince an allosaur to go have a look at Camptosaurus instead.

Now, one could argue that if the whip-lash doesn’t do any serious damage, predators will learn to blow them off as dishonest signals (we’re assuming here that having your eye possibly knocked out doesn’t count as ‘serious damage’ to an allosaur). But it’s not like the whiplash was the only weapon a diplodocid could bring to bear: the proximal tail could probably deliver a respectable clobberin’, and then there’s the zero fun of being stomped on by an adversary massing a dozen tons or more. In that sense, the whip-lash is writing checks the rest of the body can certainly cash. It’s saying, “Getting hit with this will be no fun, and if that isn’t enough, there’s plenty more coming.”

All of this is leaving aside more obvious defensive adaptations of the tail in Shunosaurus, maybe Omeisaurus and Mamenchisaurus, and probably Spinophorosaurus (although I’d feel better about Spinophorosaurus if the association of the spikes and the tail was more secure). I suspect that all sauropod tails were useful in defense, but only some sauropod taxa used that behavior enough for a morphological enhancement (club, spikes, whiplash) to have evolved. Similarly, common snapping turtles, Chelydra serpentina, will wiggle their unspecialized tongues to attract fish (I’ve witnessed this myself in captive specimens) but lack the worm-shaped tongue lure found in the more ambush-specialized alligator snappers, Macrochelys temminckii. On reflection, there are probably few morphological changes in evolution that aren’t preceded by behavior. Not in a Lamarckian sense, just that certain variations aren’t useful unless the organism is already (suboptimally) performing the relevant function.

Bonus observation: Mike noted back when that Shunosaurus and Varanus retain complex caudal vertebrae all the way out to the end. Since in this case ‘complex’ means ‘having processes that muscles can attach to’, maybe that has something to do with keeping up relatively fine motor control in your bad-guy-whomping organ. Would be interesting to compare caudal morphology between tail-whomping lizards and committed caudal pacifists (assuming we can find any of the latter that we’re certain about – maybe tail-whomping just doesn’t get used very often in some taxa, like those that have caudal autotomy). Anyone know anything about that?


  • Murphy, J. B., & Mitchell, L. A. (1974). Ritualized combat behavior of the pygmy mulga monitor lizard, Varanus gilleni (Sauria: Varanidae). Herpetologica, 90-97.
  • Myhrvold, N. P., & Currie, P. J. (1997). Supersonic sauropods? Tail dynamics in the diplodocids. Paleobiology, 23(4), 393-409.
  • Wilson, J. A., Martinez, R. N., & Alcober, O. (1999). Distal tail segment of a titanosaur (Dinosauria: Sauropoda) from the Upper Cretaceous of Mendoza, Argentina. Journal of Vertebrate Paleontology, 19(3), 591-594.

37 Responses to “Defensive use of the tail in monitors – and also sauropods?”

  1. Frosted Flake Says:

    “Know” could be too strong a term. But I recall a somewhat dramatized sciencetainment movielike examination of prehistoric professional problems which unfortunately I cannot recall the title of. The plot involved a newly minted Allosaure type guy getting smacked in the mouth by a particularly indigestible Diplodacus looking fellow. Poor little carnivore was abruptly abandoned by Mommie Dearest on the grounds that an Allosaure with a broken jaw ain’t gonna make it. But, of course, there would be no movie if he didn’t, so… there followed a long story.

    The story matters not. What does is, the use of the Diplodacus tail as a weapon in a sorta science program has come up at least occasionally. An effective weapon, at that. And Little Big Guy was shown to have a vivid recall. Later in the movie the two met again. Junior went after Big Big Guys tail. And ate it. Crooked jaw or not.

    Moving on to opine, it never occurred to me a dinosaur wouldn’t think, “Well, I’ll just smack the f*cker with my tail!” It seems like perfectly natural behavior to me. Seems to to cover an otherwise vulnerable quadrant. Particularly when one recalls the many variants of spiked and or clubbed tails attached to big extinct herbivores, as you mentioned. Though I admit up front I have never actually seen a dinosaur. So maybe my opinion isn’t worth much. Unless there is something to the idea a two footed dinosaur would be more likely to use the tail for balance than weapon. I recall being disappointed when being shown two Tyrannosaur using their tails against one another. I thought they would use the tail as counterbalance to turn toward and to shake the head back and forth while biting… that being the actual point for a two footed meat eater.

  2. Bryan Riolo Says:

    I’m afraid I’m the type of guy who, on seeing the skeletal remains of a tail powerful enough to knock down small trees, does not say, “Well, a multi-ton predator would not pay attention to that!” or “Even if said predator was hit solidly, no damage would be done.”

    Instead, I think, “Solid hit with that thing, and Allosaur or Tyrannosaur get knocked down and stomped on and/or kicked by angry sauropod hind feet claws. Bye-bye predator!”

    I’ve seen it assumed that adult sauropods were protected mainly by their gigantic size. Well, yes and no. Certain lion prides have been recorded attacking elephants and hippos-adults-and liking adult water buffalo above all other prey items. I can think of ways for theropods to attack and bring down huge adult sauropods using a one-on-one attack. If pack hunting was the norm, then even the huge sauropods could be brought down fairly regularly. Ipso facto, I can see sauropods having evolved armor and weapons, like spikes and clubs, to defend themselves. And what protected the young sauropods? The adults? Maybe. And armor? Maybe. Seems plausible to me, at any rate.

    Or if size was the only defense, then some mighty big babies hatched from those eggs! OUCH! I see sauropods as being cantankerous as a bull elephant in musth and as dangerous. They lived in a tough world; defensive weapons seem to me to have been needed.

  3. Jura Says:

    I agree with the frustration associated with the downplaying of tails as weapons (or, for that matter, anything that wasn’t more than just a counterbalance). I think it stems from a mammal-centric point of view where mammal tails are practically ornamental if they exist at all. It’s hard to imagine an animal, in danger for its life, not using everything at its disposal to dissuade its attackers. Plenty of lizards use their tails defensively (either through autotomy or as an offensive weapon). I remember a time back in the days when I still had an iguana. I was taking him out of his cage to walk around and eat while I cleaned (a daily routine). At one point he had hopped up on the back of a chair and was reorienting himself. In the process he sent a muscular wave down his tail that ended in the tip slapping my arm (it left a little red welt for a while). Even though my iguana wasn’t attempting to be defensive, just this nonchalant, unintentional, whiplash was enough to remind me of how painful these tails can be. It’s amazing what the addition of soft-tissues (such as keeled scales) can do to increase the effectiveness of a sinuous tail.

  4. Yes, yes, yes!
    Komodo dragons will hold their tails high and flexed 180° (tip pointing to snout) and run away when hunted – and as soon as the aggressor gets into range they will whack their tails around. Hard enough to sting human ankles, and certainly hard enough to hurt really good on a mammal’s nose – or take out an eye.

  5. Mike Taylor Says:

    “Plenty of lizards use their tails defensively (either through autotomy or as an offensive weapon).”

    For a 15-tonne diplodocid with two tonnes of that mass in the tail, caudal autotomy could be an offensive weapon. Just drop that bad boy on an allosaur, and watch him struggle to get up.

    (Note: this scenario is more the kind of thing that Bob Nicholls might draw during a Stinkin’ Mammal talk that a serious palaeobiological hypothesis.)

  6. stupendousmanic Says:

    The movie mentioned in post number 1 sounds like “Dinotasia”.

  7. Mike Taylor Says:

    I think it might be an episode of a recent three-part “documentary” series whose name eludes me for the moment. Maybe something like “Dinosaur nation”.

  8. Dinosaur Revolution. Dinotasia was a re-release of the footage with Werner Herzog narration.

  9. Matt Wedel Says:

    For some reason, “Dinosaur Nation” cracks me up. That was a Janet Jackson album, I think.

    Actually, it makes me want to make a Xenoposeidon t-shirt that says, “Xeno for president 2016: let’s put a real alien in the White House!”

  10. Jon Says:

    The new world version of monitor lizards (genus Tupinambis) are from the group commonly called “whiptails” and routinely whip at attackers. They also writhe their tail as a warning system.

    Maybe most impressively, they use their massive tail as a counterweight to run bipedally. Often to charge at attackers. Below’s a video of such:

  11. Mike Taylor Says:

    If only you could make such a T-shirt, Matt! Sadly the NHM’s photograph-copyright policy makes it impossible (at least, without first negotiating a contract with the commercial arm of the museum, which I would imagine takes us right back to “impossible”.

  12. Forgive me if I’m wrong, but I am pretty sure the Black and White Tegu belongs to the Teiidae, which is in the group Lacertoidea, not Varanoidea (group which includes the Varanus genus), which is a subset of Anguimorpha.

  13. Interesting. Many lizards use their tail for defense (Pogona vitticeps and Iguana iguana, for example). Crocodiles also whip their tails when distressed, and, as they are archosaurs, I find that they are better examples to argue for tail-whipping among sauropods.

  14. Here is a video of an Alligator using its tail for defense:

  15. How about a shirt that says “V for Laminae”. We can censor the vertebrae with a Guy Fawkes mask :D.

  16. Jura Says:

    I don’t think anyone was suggesting that tegus were varanids, only that tegus are another example of a tail-whipping lizard. That crocodylians also whip their tails is good, but I wouldn’t discount using lizards. Crocodylians whip their tails, but birds don’t (and can’t), so we only have one half of the bracket to work with (a level 2′ inference). That crocodylians and lizards both whip their tails makes the inference a bit stronger by suggesting that it could be a diapsid trait in general (though I would also chock it up to having an appendage and using it in times of duress). Anyone know if pangolins or any of the few other mammals with sizable tails (besides whales) ever whip them?

  17. anyone who has that amount of mass driven by that amount of muscle and with that range of motion available would be a total moron not to use it to whack attackers.

    ’nuff said ;)

  18. Allen Hazen Says:

    I suppose Allosaurids and Tyrannosaurids may not have been as sensitive around the face as typical mammals are, but even a near miss to an eye could inflict a painful wound. (And if the wound is above the eye, blood flowing into it causing temporary blindness.)

    Military types have the concept of “mission kill”. You don’t have to sink/shoot down a battleship/bomber (that would be a “kill”): if you do enough damage to keep it from completing its mission, that’s good enough for tactical purposes. (Examples: making a fighter-bomber drop its bombs early so it can manoeuvre like a fighter, or the battleship USS South Dakota, whose minor and superficial damage at Savo Island included its radar, so it never fired its big guns.)

    So: even if the tail doesn’t do serious, permanent, damage to an attacking Theropod, it can “mission kill” it, letting the Sauropod get back to stripping foliage.

  19. ncmncm Says:

    My concern with this notion is as was expressed in the classic 1958 cinema vérité “Queen of Outer Space” (starring Zsa² Gabor): “How could they aim it?” With such a distended nervous system, it is not hard to believe in coordinated rhythmical motion on even ground, but with round-trip time approaching a full second, Indiana-Jones-style precision seems hard to support.

    Furthermore, wouldn’t we expect to find typically fractured and healed distal caudals if they were abused at supersonic rates?

    This is not to argue with the notion of codswalloping assailants with the heavier bits, or even of taking advantage of the barn-sizedness of targets.

  20. Matt Wedel Says:

    “How could they aim it?” With such a distended nervous system, it is not hard to believe in coordinated rhythmical motion on even ground, but with round-trip time approaching a full second, Indiana-Jones-style precision seems hard to support.

    Several things come to mind. First, round-trip travel time is not at issue. We’re not talking about how fast the sauropod tail could respond to a stimulus that affects the tail, but rather how fast the sauropod could move its tail in response to a visual stimulus. Second, the full-second round trip travel time would only apply to Amphicoelias-class gigapods. The fastest nerve conduction times are 120 m/s, so for something like Diplodocus or even Supersaurus we’re only talking about 1/4 to 1/3 of a second to get a response from the brain to the tail muscles (which are proximal to the whiplash). Third, tail-whipping may have been more important for juveniles and subadults that lacked the sheer bulk to crush potential predators, and in those smaller individuals the distance and therefore the nerve conduction time would have been less.

    BUT I think your general point is solid: sauropods may have been fairly crap at aiming their tails. But depending on the speed of the encounter, they may have had time to get more than one lick in, and as Allen Hazen pointed out, each swipe is a chance at a “mission kill” for a theropod. Only in this case, having your eyeball destroyed is probably more of a “life expectancy kill”. Extant predators are often surprisingly conservative in their behavior, and tend to avoid encounters that could be career-enders (unless driven by severe hunger–lions vs elephants, etc.). As I suggested in the post, what seems to us like an ineffective weapon might still do the job of dissuading potential attackers.

    Furthermore, wouldn’t we expect to find typically fractured and healed distal caudals if they were abused at supersonic rates?

    Now you’re talking about a separate hypothesis. Myhrvold and Currie (1997) weren’t arguing for a defensive use of the tail. But you’re right, we would expect the distal tail to fray if it was regularly breaking the speed of sound, and this is something that Myhrvold and Currie explicitly address. They hypothesized that since such fraying would be debilitating for the caudal vertebrae, diplodocids might have had a “popper” of skin or keratin that extended tens of centimeters beyond the end of the caudal vertebral series.

    Ultimately, I find the suggestion of supersonic whip-cracking unsatisfactory for two reasons. First, defensive use of the tail might or might not produce injuries to the distal caudals, depending on how vigorously the tail was used and how often (given sauropod fecundity, the “rare predator” effect may be relevant here), but supersonic cracking definitely would. Yet Myhrvold and Currie consider the absence of distal tail pathologies as stronger evidence against defense than against their own hypothesis! Frankly, I doubt if we have enough complete whiplashes to say anything about rates of injury. It just struck me as odd that they skipped over the fact that the absence (so far) of pathological whiplash series is evidence against their own hypothesis–unless we accept the presence of a wholly speculative “popper” extension.

    My other beef with the supersonic cracking hypothesis is that it doesn’t explain how or why whip-tails evolved to the point of being able to produce a supersonic crack. Breaking the sound barrier is NOT like evolving an eye, where a collection of photoreceptors is still better than nothing, and gradual improvements in the structure give gradual improvements in performance. A tail can either crack supersonically or it cannot. IIRC, Myhrvold and Currie (1997) do not explain why the intermediate morphologies, that could not yet produce a supersonic crack, would have been favored.

  21. LeeB Says:

    If the whiplash tails evolved as a defence mechanism for small or medium sized juvenile sauropods which are subject to predation pressure then the supersonic tail crack could just be a side effect of the increased size of the tail in adults.
    Of course it could then be selected for whether to intimidate predators or in intra-specific dominance contests, as it would be an honest signal of the tail reaching a certain size and length.

    A related question might be if you have a 10-15m long tail with a thin whiplash at it’s end how slowly would you have to move it to avoid inadvertently creating a supersonic crack?

    And if you are a herding animal and one of the herd members creates a crack with it’s tail you are certainly going to notice it, and it would be easy to build the sound into a dominance display.


  22. Mike Taylor Says:

    anyone who has that amount of mass driven by that amount of muscle and with that range of motion available would be a total moron not to use it to whack attackers.

    Right. It’s like the idea that Triceratops, conveniently armed with monstrous head-mounted weaponry, chose not to use them for defence. It only makes sense if you assume that Triceratops was a total moron.

  23. Mike Taylor Says:

    Defensive use of the tail might or might not produce injuries to the distal caudals, depending on how vigorously the tail was used and how often.

    I note that in many, many flagellicaudatan specimens, the distal whiplash is absent. Obviously that’s just due to regular-ass taphonomic damage in many cases, but in others it may represent injuries sustained in life.

  24. Bryan Riolo Says:

    Why NOT a Xenoposeidon T-shirt?

  25. Mesozoic Cowgirl Says:

    The first thing I thought of when I saw the title was caudal autotomy. I’m so glad it wasn’t just me. >_>

    “Anyone know if pangolins or any of the few other mammals with sizable tails (besides whales) ever whip them?”

    I don’t think these are the type of tails or presumably the type of whipping you meant, but horses (and similar) of course use their tails to defend against biting insects – anything from swishing the tail lightly around their hind end to flicking it all the way up, depending on how bad the bugs are. However, they’ll also tail-swish when they’re irritated – if they’re in pain, if they’re being ridden by someone who doesn’t have it quite right, or if they just plain don’t want to go along with what’s being asked – and if you happen to be in the right place to get caught by said swish, it does sting quite a bit. (Ask me how I know.)

    They’re also stompy and full of bitey chompy teeth! Really, if I didn’t know the difference between a dinosaur and a horse, and you led me up to one and tried to convince me it was the other, I might be inclined to believe you.

  26. Mike Taylor Says:

    Bryan Riolo asks:

    Why NOT a Xenoposeidon T-shirt?

    This is why. In fact, for a while before that post came out, we did have Xenoposeidon shirts for sale, but we had to take them down. For the same reason, the highly sought-after Brachiosaurid cervicals of SV-POW! T-shirts are not on general sale. It’s a shame.

  27. albertonykus Says:

    On pangolins: I’ve read anecdotal accounts at least of them weaponizing their tails. John Hutchinson provides one such quote in this blog post.

  28. Bryan Riolo Says:

    Xenoposeidon T-shirt…does anyone own the copyright on the creature itself? I assume it was a dinosaur. Might even be a sauropod. Ipso facto, a T on a dino was what I was thinking of, not a photo of anyone’s fossils.

    In other words, with the pertinent information, I can design a T for you…an ORIGINAL design.

    So…you want one, let me know. :o)

  29. Mike Taylor Says:

    Well, of course no-one owns copyright on a creature. You are welcome (as is anyone) to draw a sauropod, call it Xenoposeidon, and put it on a T-shirt. But since all we have to go on is that one vertebra, all pictures of which are copyright the NHM, I’m not sure how you could proceed.

    That said, I’d love to find out!

  30. LeeB Says:

    Imagine what the group defence of a herd of sauropods would be like if they formed a circle with their heads inwards and tails outwards, lifting their necks up to look back over their shoulders and multiple whiplash tails striking out at any predators stupid enough to approach.
    Stegosaurs could do the same thing although due to their shorter necks they may have had more difficulty seeing the predator(s) approaching; perhaps they looked between their legs to judge when to strike out with their tails.

    That could perhaps make an interesting artwork.


  31. Bryan Riolo Says:

    Well…what WAS Xenoposeidon? A titanosaur? A giant predator looking to eat foreign dinosaurs? The design can be serious or it can go hog wild. Did it have a Green Card? :oD

  32. ncmncm Says:

    I won’t quibble with any of your conclusions, but I feel honor-bound to explain what nerve impulse roundtrip time has to do with aim. In short, biological machinery is pathetically imprecise. We get along anyhow because we have systems to correct continuously as things drift off point. In this case, the tail starts on its way toward a rendezvous with the attacker’s peepers, but is a bit off. (Maybe the target is moving, maybe we weren’t precisely sure where we started.) Our protagonist observes this, visually, and sends corrective signals, which must adjust for the transmission time of the signal. The longer that time is, the more difficult the calculation, and the less likely a correct answer. There is time for only a few corrections, at best.

    Insects do superbly with very little brain because they can correct so quickly that a trivial linear approximation is good enough. I assume birds get along with less brain than similarly-sized mammals because theirs are better-organized than ours. Even assuming sauropods shared birds’ presumed cerebellar organizational advantages, though, there doesn’t seem enough brain there for precise targeting under long delays.

    But I would prefer to be wrong.

  33. Jura Says:

    One thing worth keeping in mind is that, in this particular case, we are looking at a multi-tonne sauropod attacking a multi-tonne theropod. Between the theropod’s reaction time (and inertia) and the sauropod’s adjustment time (and inertia) I suspect the respective delays from both parties probably made up for any potential communication issues between the sauropod’s head and the tail (or rather the pelvic central pattern generator). Sauropod’s may not have been able to knock a tin can off a fence post, but I’m sure they were able to routinely make tail contact with the large bodies of sauropod-hunting theropods.

  34. Bryan Riolo Says:

    Jura…sounds to me like you’re right on the nose, er…tail!

  35. Mark Robinson Says:

    Sauropods don’t need to knock tin cans off fence posts. They achieve their objective by taking out the whole fence.

  36. […] monitor lizards are known to whip their tails to strike back at intruders – in fact, there’s at least one case in which a monitor delivered a stinging blow to a […]

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