Why Giraffes Have Long Necks

When American school children learn about evolution, it’s not atypical to discuss giraffes, whose long necks distinguish them from the rest of the animal kingdom.  The theory: there were short-necked giraffes and long-necked ones, and the genetic trait of the latter survived, as that gene type had significantly better access to food.  (Giraffes eat twigs, fruit, and grass, and there is often more of the former two at higher heights.)

It turns out that this theory isn’t quite right.  It turns out that while South African giraffes use their long necks to get to better food, those in Africa do not — even when food is otherwise scarce.  And as Zoologger points out, “if giraffes evolved to reach higher branches, we might expect their legs to have lengthened as fast as their necks, but they haven’t.”   So, where did all the short-necked giraffes go?  Why did the longer-necked folk win out?

Sex, of course.  No, no, giraffes don’t procreate by necking.  Rather, one theory is that giraffe males swing their necks at each other, fighting, in effect, for the attention of female giraffes.  (A study of sauropod dinosaurs — think brontosaurus/apatosaurus, depending on when you learned about dinosaurs — suggests that’s why they have such long necks, too.)   Giraffes are built for these battles, with extra-thick skulls attached to their long necks. But don’t take their word for it:  Watch a giraffe neck fight right here, fromAnimal Planet‘s YouTube channel.

And it turns out that the giraffe with the longer necks are more likely to win these brutal fights.  A 1996 study concludes that these fights are not random acts of violence, but rather, a successful way to attract a female mate.


Bonus fact: Giraffes gestational cycles run between 400 and 460 days, or about 13 to 15 months.  At birth, the newborn calf is about six feet tall and, because mother giraffes give birth standing up, they quite literally fall to the ground as they enter this world.

From the Archives: Invisible Polar Bears.  Giraffes are cool, but so are polar bears, no?

Related: A huge, huge, plush giraffe.  A bargain at only $67.