Biologist examines evolutionary reasons behind female bovids growing horns
University of Massachusetts evolutionary biologist Ted Stankowich, a lecturer and former Darwin Postdoctoral Fellow, offers a new possible explanation as to what uses female animals with hooves have for their horns.
In his article entitled, “Evolution of weaponry in female bovids,” which was published in the August 2009 edition of The Royal Society Journal, Stankowich proposes that female bovids that live in open habitats or are conspicuous because of their size are significantly more likely to have horns than small species or species that can hide in closed habitats.
According to Stankowich, the research, which was done in collaboration with Tim Caro of the University of California Davis, is the first to offer a comprehensive hypothesis that analyzed data taken from all 117 bovid species.
Some examples of common horned bovids are cattle, goats, gazelle and antelope.
“We went through the scientific literature on different species and gathered data on variables like group size, how large the animals were, if they lived in open or closed habitats, and then we analyzed the data statistically,” Stankowich said.
The researchers also considered other factors such as territoriality and the group sizes of the species. “Our goal was to explain every case of horns in bovids,” Stankowich said.
“We hypothesized that species that are taller and live in open habitats are more exposed, visible for longer distances and would be more likely to benefit from the presence of horns for defense against predators,” said Stankowich in the article.
Stankowich used phylogenetic analysis, or comparison of ancestral genetic relationships between species, and contrasted existing hypotheses to test his hypothesis. He said his hypothesis explained the presence of horns in 80 out of 82 horned bovid species.
He added that his research did not provide an explanation for antlers in deer, which are cervids, not bovids.
“This is the first paper to build into account whether females are territorial or not,” said Stankowich.
Stankowich’s research revealed that territoriality did play a small but significant role among a genus of bovids called duikers, a type of small antelope.
According to Stankowich’s article, researchers have proposed a variety of competing hypotheses to explain the presence of horns in female bovids. Some researchers believe females use horns for competition with other females for food. Meanwhile, others argue horns are purely for defense against predators.
Niina Heikkinen can be reached at email@example.com.