I promised more shots of the juvenile elephant in the Berlin Zoo. Here’s how he got back down from the rock he had climbed on, and some musings on an elephant locomotion study.
There is a Current Biology paper from 2006 by Wall et al. titled “Elephants avoid costly mountaineering” (free PDF here), which purports to show that elephants prefer detours to climbing steep slopes. The authors also claim that “even minor hills are considerable energy barriers for heavy animals”. They show this by energy calculations – and that’s where suspicion immediately raises its nagging ugly head in my brain! While acknowledging that other factors exist (overheating, risk of injury, lack of water or unsuitability of forage) the authors “..suggest that energetic considerations could be one of the main factors..”
To show this Wall et al. show a map of elephant tracks (oh how I love GPS! It helps us so much in studies on living animals!), and golly! the beasts don#t climb the f-ing hill! Here’s the map, from Fig. 1 of Wall et al. 2006:
Pretty obvious, hu? But if you check out part A of that figure, an arial photograph of the hill (HR version here), it is easily visible that this is not a harmless knob in the landscape, but rather quite a ridge! Now, what about the terrain being physically impassable to elephants? Wouldn’t that be a reason not to go there, energetics and all other stuff be damned? The fact that the “hill” is in fact a very steep-sided mountain would indicate to me that energy is not the main issue. We’re not taking about elephants walking up or down hills, but about them rock-climbing. And things like limited range of motion in the limbs, absence of grapsing ability in hands and feet, and risk of injury in case of a slip or fall must certainly be key factors. Energy? Well, maybe it would be a factor if the hill wasn’t too steep to climb in the first place! It is a bit like saying “humans avoid costly mountaineering” because we prefer not to climb ladders without rails!
OK, in the end it is very likely true that large animals take a different view or their environment than smaller ones, and avoid going up and down all the time – but then, they have longer limbs and can thus deal with obstacles a lot better. To them, somewhat rough terrain “looks” smoother, too. Where a rabbit must jump high, an elk can walk and pull the feet up a bit more. In summary, energetic considerations are one of many factors, but in my opinion certainly not as dominant as the Wall et al. paper suggests. They picked an absurd case, which at first glance gives apparently crystal clear evidence. If they had taken a hill that was less steep I expect the elephant routes to be less clearly avoiding it.
So where does that leave us? As has been pointed out by Ren et al. (2008) (open access to paper here) that elephant limbs aren’t half as stiff as people think. And if you think of elephant tricks as they used to be commonly shown in circuses you’ll realize that they can stand on very small areas, with all feet touching.
But elephant feet aren’t suitable to all substrates, and the huge weight means that they need to be more cautious than most other animals: the same sort of fall will hurt them much more, because material properties do not scale up with size.
Imagine a cat falling on its side, compared to an elephant: the distance is much greater for the elephant, and the mass, thus the impact energy is much bigger. And while the musculature covering the shoulder is also thicker than in a cat, it is not proportionally thicker compared to the impulse transferred on impact. Thus, an elephant falling over is more likely to damage his shoulder blade than the cat.
and thus our little friend gets back to flat ground very carefully!
BTW: it’s fun to save all climbing elephant pics to one folder and run them as a slide show. It shows nicely how the descent works 🙂 EDIT: trust David Maas to do it before I can google for a program that can do it for me: www.drip.de/?p=1783
I have some more shots of rather artistically inclined elephants, but I’ll save them for a rainy day post.
Fantastic photos, thanks for posting!
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wow. faster than google! 😀
I’m honored. Cool sequence.
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Very interesting, as always!
In hypothetically comparing these photos and the energetics study with sauropods, the possible role of the differing life histories between elephants and sauropods intrigues me. I might assume that the greater degree of parental care in elephants would disincline juveniles from accessing places that adult members of the herd could not access. Maybe juveniles could climb a hill that adults no longer would be able to climb up or down from. If we assume that young sauropods did not cling to their parents as elephants do, they may have traveled through much more varied terrains than adults. I know this gets into untested, or untestable, territory. But the final figure in the Wall et al. study shows the different energetic requirements between a 100 kg animal and a 5 ton animal. Granted, a newborn elephant already weighs 100 kg. In sauropod life histories, though, both those weights would apply to juveniles of the same species. If all else is equal (which it isn’t) and energetics are the sole deciding factor (which they aren’t), then sauropod juveniles can climb the highest mountains!
Also, from the Wall study, it’s noteworthy that in figure 1 they show an outline of the mountain compared to the trackway image you post here. Comparing figures 1B and 1C, there is actually a lot of activity at the edges of the mount, so elephants are not entirely avoiding slightly steeper gradients.
Demetrios, you picked up an important point with the “edges”! And it is not really surprising that elephants go as far up the hill as they can, because (as shown and stated by Wall et al.) the hill is much greener than the surroundings. Thus, once the forage gets scarce, the hill becomes more attractive, and energetic considerations and fear of injury etc. will be weighed less heavily than in times of ample fodder.
And yes, I can imagine tiny sauropod babies going places no adult sauropod in its right mind would dare to wander into. After all, hills may have been places of lusher, thus denser foliage because of reduces grazing (I always cringe when I type that word in connection with dinosaurs, it too obviously stems from “grass”), and accordingly cover. And huge theropods, those from whom a baby sauropod would be meals on whee… erhm, limbs, would also be less inclined to climb hills.
Concerning theropod access to steeper territories: Could the energy “scape” from Wall et al. figure 2 apply to bipedal theropods, or even quadrupedal dinosaurs, as it applies to quadrupedal mammals, or are the energetics too different?
Well, this is getting a bit far ahead of my current research….. but obviously, large theropods fare worse climbing up and down hills than medium sized ones, whereas small ones may quickly get into the rock-climbing instead of walking uphill problem, if the terrain is rough. The general rule certainly applies!
btw: I had a quick look at your site, and love the comparison of sauropod dinosaurs, an elephant, and a guy holding a baby sauropod. That’s a very smart way of highlighting the size&growth difference between mammals and dinosaurs! I look forward to having a more thorough browse of your art (a term I often use disparagingly, but in this case I mean it as praise). 🙂
Thanks for your compliments! … And you put my portfolio in your links! Wow! Awesome, thanks!
I’ve thought a lot about updating that sauropod drawing; it was commissioned in the early 2000’s, so preceded the Taylor et al. 2009 elevated necks paper. The commissioner requested that the necks accord to what had become the convention, following Stevens. One material benefit is that the Brachiosaurus’ neck could more easily fit and keep the drawing at a manageable size. It looks a bit dated now, though (especially the Dicraeosaurus). Do you think it’s a glaring problem?
At any rate, I always enjoy your blog and thanks again!
No, I don’t think there are glaring problems with that drawing. it makes its point very nicely, and it is, after all, a few years old.
Thanks for the praise – I aim to please 😉
Assuming you’re referring to this picture:
It looks good to me! No, I don’t believe that the postures you illiustrated were the habitual ones for any of the sauropods; but they were perfectly attainable, and no doubt often adopted when low-browsing and when making the transition between high browsing and drinking. So there is no need to update the picture.
I only stumbled across this blog today, so late to this one, but I laughed out loud when I saw the aerial picture of that ridge. You have to suppose it hadn’t occurred to the authors to try to see what the ‘hill’ actually looked like.
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