Giraffes grew long necks to headbutt rivals when mating

GIRAFFES grew long necks so they could headbutt love rivals in mating battles, according to a study.

The neck of the modern giraffe, the tallest land animal and largest ruminant on Earth, has long been considered a classic example of adaptive evolution and natural selection since Charles Darwin first developed the concepts.

It is believed that competition for food drove neck elongation and allowed giraffes to browse for treetop leaves in the African Savannah woodlands.

But a Chinese research team say their long necks grew so they could compete for mates, rather than reach for food.

An analysis of an early giraffe ancestor’s unique head and neck fossils – disc-shaped helmet-like headgear and complex head-neck joints – suggests sexual selection, driven by competition among males, may have also contributed to neck evolution.

As observation of giraffe behaviour increased, scientists began to realise that the long neck of giraffes serves as a weapon in male courtship and that may be the key to the giraffe evolutionary mystery. The longer the neck, the greater the damage to the opponent.

Researchers from the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) of the Chinese Academy of Sciences conducted their study on Discokeryx xiezhi, an early giraffoid.

The fossils analysed in the study, published in the journal Science, were found in early Miocene strata from about 17 million years ago, on the northern margin of the Junggar Basin in Xinjiang. A full skull and four cervical vertebrae were part of the find.

Author Prof Deng Tao, of IVPP, said: “It is possible that, among giraffe ancestors during this period, mating males developed a way of attacking their competitors by swinging their necks and heads.

“This extreme struggle, supported by sexual selection, thus led to the rapid elongation of the giraffe’s neck over a period of two million years to become the extant genus, Giraffa.”