Image: Courtesy of Donald Henderson and Darren Naish
If you dropped a giraffe into a deep pool of water, would it float, or would it sink? If it could float, would it swim briskly and confidently to the nearest bit of land, or would it flail around helplessly and drown?
Strange as it may seem, the floating and swimming abilities of giraffes—or rather their supposed lack of floating and swimming abilities—have often been written about by experts. It has been asserted that giraffes “sink like stones” and “cannot swim, even in an emergency,” and that “rivers are an impassable barrier to them.” Although a few rare photographs and segments of film show that giraffes will wade into deep rivers when they have to, definite observations of them swimming have yet to be reported.
One way to examine the behavior of giraffes in water would be to push one into a deep pool and observe the results. Ethical and practical concerns make this hypothetical experiment impossible, so I thought of another solution. Inspired by sheer curiosity, I approached Donald Henderson of the Royal Tyrrell Museum of Palaeontology in Drumheller, Alberta, who had created a three-dimensional computational model of a giraffe for another project and had also tested the buoyancy of assorted living and extinct animals by using flotation-simulating software. Could Henderson, I wondered, test the buoyancy of his “digital giraffe” in the same way? If he could, we might be able settle this question once and for all.
To compare the model’s aquatic behavior with that of other animals, we performed calculations to determine an immersed giraffe’s centers of mass and buoyancy, the resistance it encountered when moving its limbs, and the friction it encountered across its whole surface. We had to take account of the giraffe’s unusually shaped lungs, the size of which has been the subject of disagreement among experts. Having tweaked the model to make it as plausible as possible, we were ready to see whether the giraffe could float and swim. Our analysis and conclusion appear below:
- The heavy forelimbs and shoulder region would pull the front half of the animal downward, thereby forcing the neck into a near-horizontal posture.
- The giraffe’s relatively high density, particularly in its limb bones, would make it sit very low in the water, and it would suffer from high drag.
- The animal would have to hold its head upward at an uncomfortable angle, and it would be unable to move its neck up and down in concert with its limb movements.
Conclusion
Giraffes can float, but they would be clumsy and unstable in the water.
Discussion
Testing the swimming abilities of a giraffe might seem like a frivolous exercise. But analyzing the question is of great interest to anyone engaged in the biology or management of the animals. Our study also showed that scientists could rely on computer simulations to help examine fascinating questions in biomechanics.
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8 Comments
Add CommentThat doesn't look right on its face, an doesn't correlate with other animals posture in the water. The hindquarters should be lowest, because the density of that section of the body is highest. The forequarters are large, but overall density is lower because of the by lungs. So the giraffe should sink down with its head upward roughly in the posture in which it stands. But the massive long neck should cause it to ride low in the water with just the upper part of its neck sticking out. The biggest problem the giraffe should have is that its lungs would have to work against pressure of water which would make breathing difficult.
Reply | Report Abuse | Link to thisOf course something not "looking right on its face" doesn't really prove it is correct or incorrect. Lots of things that are anti-intuitive are still true, and just because something is the norm, doesn't mean it is impossible to vary from it.
Reply | Report Abuse | Link to thisIt seems reasonable to me that a giraffe would sit in the water somewhat differently from other animals because its body structure is balanced differently... they are kind of noted for being shaped in an unusual way in fact.
If your argument against this study and simulation of the issue doesn't have any other points beyond that, I'm afraid you haven't convinced me.
I'm not saying they are right, as I certainly don't know one way or another, but unless you know of actual flaws in their simulation, approach, or facts, I'll take their conclusions over someone who is just saying basically "because I said so."
But those are just my thoughts on the matter, I admit to not being at all knowledgable in this field.
Haven't read the full article yet...but from the teaser, I would have to question the "unethical" statement...
Reply | Report Abuse | Link to thisWhat would be wrong with taking a zoo animal and supporting it with a crane(not the bird;-) and lower it into a pool and see what it does....
Thoughts anyone....Might verify or disprove the "model" used....
There was or is little evolutionary advantage for them to float or swim when one considers how very few rivers or portions of rivers in Africa/Arabia would have been or are uncrossable to giraffes due to depth. As a unique specialist feeder, other adaptions (growing taller requiring more bone with insignificant lung capacity increase) would have been more successful. Relative dearth of deep lakes (essentially only the "rift valley lakes") and off-continent islands add to this argument.
Reply | Report Abuse | Link to thisGiven the burning scientific interest in the issue, some zoo that hosts an adult giraffe could stand ready to hoist it into a nearby pool soon after its death from natural causes, before decomposition has had time to affect its buoyancy significantly, and at least get an answer to the density question. In many zoos the hippos are housed close to the giraffes, so "nearby pool" isn't as silly as it sounds. I'm sure precautions could be taken to prevent transmissions of diseases to the hippos through the water.
Reply | Report Abuse | Link to thisCouldn't giraffes just walk across rivers? They do reach a height of 25 feet.
Reply | Report Abuse | Link to thisEver try to walk through flowing water deeper than your waist? Even if you don't float (the unanswered question about giraffes) or tip over, your weight presses down less on your feet and your reduced coefficient of friction makes forward progress impossible.
Reply | Report Abuse | Link to thisThe image (Image: Courtesy of Donald Henderson and Darren Naish) does not say whether the giraffe is dead of alive. If the giraffe is dead, the heaviest part of the animal --- the head --- would be submerged in the water, and the lungs would be filled with water. I would not say that the limbs of the animal have the highest density because they are bony as claimed. Inside the bones, there are bone marrows, the overall density of which could make them float, I think. Therefore, a dead giraffe in water would be upside down, the head being at the lowest point, the limbs being at the water surface. By the same token, the image must be one that shows a living giraffe, struggling to maintain its head above the water in order to yell for help and to breathe.
Reply | Report Abuse | Link to thisHave you ever seen dead fishs in the water --- mostly up side down with belly facing the sky?