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bendy


Member

Posted Sun Dec 6th, 2009 7:26pm Post subject: Why DO giraffes have long necks?

A recent paper from the Journal of Zoology suggests that sexual selection/ male-male combat has not driven the evolution of long necks in giraffes. If it had, we'd expect males to have proportionally longer necks than females, which they don't.

Abstract:
The evolutionary origin of the long neck of giraffes is enigmatic. One theory (the 'sexual selection' theory) is that their shape evolved because males use their necks and heads to achieve sexual dominance. Support for this theory would be that males invest more in neck and head growth than do females. We have investigated this hypothesis in 17 male and 21 female giraffes with body masses ranging from juvenile to mature animals, by measuring head mass, neck mass, neck and leg length and the neck length to leg length ratio. We found no significant differences in any of these dimensions between males and females of the same mass, although mature males, whose body mass is significantly (50%) greater than that of mature females, do have significantly heavier (but not longer) necks and heavier heads than mature females. We conclude that morphological differences between males and females are minimal, that differences that do exist can be accounted for by the larger final mass of males and that sexual selection is not the origin of a long neck in giraffes.

Journal of Zoology
Volume 278 Issue 4, Pages 281 - 286

Cheers


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Auron


Member

Posted Fri Dec 18th, 2009 6:20am Post subject: Why DO giraffes have long necks?

it's so their feet reach the ground.

I saw a little bird in search of food,
The winter's cold; he'll die I think.

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nicole68


Member

Posted Sat Dec 19th, 2009 3:04am Post subject: Why DO giraffes have long necks?

i would think that depend on some situation

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Auron


Member

Posted Sat Dec 19th, 2009 4:23am Post subject: Why DO giraffes have long necks?

In a sligtly less smart arse guess

its easy to accomodiate for female's having long necks:

having a long neck probibly wouldn't be enough of a disadvantage to drive a difference beteen the sexes.
Do giraffes need long necks to reach food aswell? if so, females would need to be able to compete with males or starves, therefore, the one with shorter necks would die awayways reguardless of weither their necks are just necks and not weapons of choice for battles of dominance. Male may compete with neck lenght then, but the females would need to stay on par in order to reach food.

I saw a little bird in search of food,
The winter's cold; he'll die I think.

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James Patrick Joyce


Member

Posted Sat Dec 19th, 2009 6:43pm Post subject: Why DO giraffes have long necks?

Journal of Zoologywas quoted as:
Support for this theory would be that

    males invest more in neck and head growth
than do females.

We have investigated this hypothesis... by measuring head mass, neck mass, neck and leg length and the neck length to leg length ratio. We found no significant differences in any of these dimensions between males and females of the same mass,

although mature

    males... do have significantly heavier
(but not longer) necks and heavier heads than mature females. We conclude that morphological differences between males and females are minimal, that differences that do exist can be accounted for by the larger final mass of males and that sexual selection is not the origin of a long neck in giraffes.

They conclude.

They were supposedly looking for a greater male investment in neck and head growth.

They found a greater neck and head growth in males.

They dismissed that on the grounds that male giraffes tend to have heavier neck and head growth, then females.

???

There is no rule that males, in general, will be bulkier than females. I’m not sure I can see the reason to dismiss the bulkier necks. If the females <b>don’t</b> have bulkier necks, then it is abundantly obvious that bulkier necks are not necessary, for a giraffe’s survival. Thus, I would think, the bulkier necks in the males must serve a purpose. And the purpose would, at least,

    suggest
a possible connection with sexual jockying.

As to a reason why females have equally long necks?

An off-the-cuff, but entirely reasonable, possibility: Males go after females with the longest necks; females choose the males who win the... ummmm... necking competition with other suitors.


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