Giraffes are one of the world’s tallest animals, thanks to their extraordinarily long necks. Previous theories suggested that the need for sex or domination over other males to secure a mating partner may have led to the evolution of the long neck but a new study has dismissed this conclusion. Biologists from Pennsylvania State University have revealed that the need for nutritional needs may have driven this evolution.
‘Female giraffes have proportionally longer necks’
The researchers in their analysis found that female giraffes have proportionally longer necks than their male counterparts. It led them to believe that the need for foraging deep into trees was behind the evolution of longer necks.
Males had wider necks and longer forelegs whereas females had proportionately larger trunks and necks. Both, giraffes in captivity and those in the wild, exhibited the same trend.
“Rather than stretching out to eat leaves on the tallest branches, you often see giraffes – especially females – reaching deep into the trees,” said lead author Doug Cavener, a biologist at Penn State.
“Giraffes are picky eaters – they eat the leaves of only a few tree species, and longer necks allow them to reach deeper into the trees to get the leaves no one else can. Once females reach four or five years of age, they are almost always pregnant and lactating, so we think the increased nutritional demands of females drove the evolution of giraffes’ long necks,” he added.
Necks-for-sex theory
The “necks-for-sex” theory claimed that male competition—known as neck sparring—was the main reason why necks evolved to be longer. Neck sparring involves male giraffes swinging their necks and slamming into each other to exert dominance. Longer-necked males would have an advantage in these contests, which would encourage reproduction and the gene-passing of children.
“The necks-for-sex hypothesis predicted that males would have longer necks than females,” Cavener said. “And technically they do have longer necks, but everything about males is longer; they are 30 per cent to 40 per cent bigger than females.”
(With inputs from agencies)
Credit: Source link