CHICAGO - One simple answer to why some male lions do not have manes, or grow skimpy thatches of hair around their necks, is that the animals are trying to stay cool, researchers said on Friday.
Theories have abounded about the evolutionary purpose of the bushy manes associated with the "king of beasts." Some scientists have speculated they are designed to attract females while protecting their necks from the fangs of rivals.
But researchers at Chicago's Field Museum of Natural History said maneless or thinly maned lions in Kenya's Tsavo wildlife reserve enjoy plenty of female company.
Comparing lions in the hot, humid Tsavo reserve to those living at the cooler, higher elevations of the Serengeti plain, the researchers reported in the Journal of Zoology that Tsavo lions had smaller manes than their counterparts.
Some researchers have suggested Tsavo lions had more testosterone in their bodies which would account for their legendary aggressiveness while also hindering hair growth -- as the hormone does in bald men.
Others suggested they may have inherited the trait from now-extinct European lions that were depicted in cave paintings without manes.
Still other theories suggested that maneless lions in the forbidding Tsavo reserve suffered from poor nutrition, or a lack of water, or tore out their manes while traveling through the region's prickly underbrush or while scratching out burrs.
But the Field Museum's Thomas Gnoske and Kerbis Peterhans discounted those theories.
They said males they observed in Tsavo did grow manes but they developed later, grew more slowly, and tended not to be as bushy as their Serengeti counterparts.
The Tsavo lions' smaller manes appeared to do nothing to diminish their mating capacity, they added, observing small-maned lions serving as dominant males in prides.
"We propose that all lions develop manes in accordance with local climatic regimes," the authors wrote.
"At a certain point, cooling takes precedence over other evolutionary advantages," Peterhans said in an interview. "Hair acts inherently as a thermal insulator ... and therefore can compromise a male's ability to maintain thermal balance in extremely hot and humid environments."
Story by Andrew Stern
Story Date: 18/9/2006