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Page last updated at 10:46 GMT, Thursday, 3 June 2010 11:46 UK
Portsmouth expert proves giraffes can swim
Giraffes
Conventional wisdom is that giraffes avoid water

A Portsmouth academic has used mathematics and computer modelling to prove that giraffes can swim.

Whereas most large animals are extremely good swimmers, it has been accepted that giraffes are unable to swim or wade.

The authors of the new study hoped to test the theory by using a 'digital' giraffe rather than a real one.

No-one has ever seen a giraffe swim, but the results show they could - but would not be very good at it.

Dr Darren Naish, of the University of Portsmouth, was spurred on to find out if giraffes could swim after he took part in an online debate on the subject.

Working with Dr Donald Henderson, of the Royal Tyrrell Museum of Palaeontology in Canada, the pair built on previous work of Dr Henderson who had created a digital model of a giraffe, and had also tested the buoyancy of various computer generated models of animals.

The new study resulted from the logical decision to see what happened when a 'digital giraffe' was placed in 'digital water'. The new study is published in the Journal of Theoretical Biology.

Dr Naish said: "Many previous studies have claimed that giraffes cannot swim and that they avoid water like the plague, even in an emergency, but we wanted to put the theory to the test in proper controlled experiments."

Digital giraffe

Creating a digital giraffe involved numerous calculations on giraffe weight, mass, size, shape, lung capacity and centre of gravity. Calculations were made to discover rotation, flotation and the external surface area of a giraffe compared to a horse.

Giraffe models
The study showed giraffes would float in a peculiar manner

The authors found that a full-sized adult giraffe would become buoyant in 2.8m of water. Giraffes can wade across bodies of water that are shallower.

Dr Henderson insists: "The idea that giraffes are poor waders or will not cross rivers is untrue and there are no obvious reasons why giraffes might be more prone to sinking than other animals."

But after becoming buoyant, a giraffe would be unstable in the water due to its long, heavy legs, short body and long neck.

The unusual shape of the giraffe meant that it floated in a peculiar manner, with the long front limbs pulling the body downwards.

This forced the neck to be held horizontally and mostly underneath the water surface, so the animal would have to hold its head upwards at an uncomfortable angle.

Giraffe handicaps

Giraffes have other handicaps in the water. Horses tend to swim by trotting in the water, similar to the way they move on land.

But giraffes move on land in an unusual way, moving their neck up and down in time with their limbs, and this important neck movement is not possible in the water.

This led to the conclusion that giraffes are probably very poor swimmers.

Giraffes also have 13% more surface area than a horse, mostly because of their longer legs, leading to greater drag.

A further complication is that larger animals have slower muscle contractions, making it difficult for a giraffe to paddle fast enough to move forward.

"Feasible" to swim

Dr Naish said: "Our models show that while it's feasible for a giraffe to swim, it is much harder than it is for a horse.

"It is fair to say that giraffes might be hesitant to enter the water knowing that they are at a decided disadvantage compared to being on solid ground."

While the team admit this research is unlikely to have many practical applications, they stress that that computer simulations of animals - rather than real animals - can sometimes be used to answer interesting questions.




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