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.