It's long been known that lions with long, full manes get the girls. Now, an innovative study based on zoo animals all across America shows for the first time that cold temperatures help the king of the beast grow his mane long and thick and more appealing to potential mates.
In fact, up to one-half of the length and density of a zoo lion's mane can be attributed to temperature, rather than nutrition, social factors, individual history, or genes, according to a study that will be the cover story of the April issue of the Journal of Mammalogy. That journal will be published on April 13, 2006.
Dense manes retard heat loss as would a scarf or fur hat. Zoo lions in hot climates adapt with smaller, thinner manes. Those in northern zoos never overheat so no reduction in their mane is necessary. Those in southern zoos occasionally overheat, so a differential hair growth rate keeps their manes relatively thinner.
These differences in mane conditions are not the result of natural selection. Rather, they are a sign of a flexible trait that can vary to match local conditions.
Like a buck's antlers or a peacock's tail feathers, the lion's mane primarily serves to attract females and intimidate male competitors. But it comes with a cost: a full mane takes energy to grow and maintain; gives away location to prey; makes maneuvering through bramble difficult; harbors parasites, and, as we have said, retains heat. Overheating explains why lions in colder climates have longer, thicker manes: the heat-retention cost of a full mane is less for lions in cold weather conditions than it is for lions in hot weather conditions.