Washington, Sept 27: A new study by scientists at Field Museum shows that wild lions generally develop manes in accordance with local climate regimes.
In an article published in the Journal of Zoology, the researchers have shed light on several longstanding misconceptions regarding the controversial topic of mane variability among wild lions.
They said that in equatorial east Africa, where the climate is determined by elevation, lions with the most profuse manes occur at the upper limit of their altitudinal range. Whereas, similar aged males in the lowest and warmest environments like Tsavo typically carry only modest or scanty manes.
The researchers said that the majority of lions in regions like the greater Tsavo ecosystem, which is known for "maneless" lions, did appear to acquire respectable manes eventually, contrary to most recent popular and scientific accounts of the lions from that region.
"We knew about the climate/elevation correlation since we were the first to publish those preliminary results in GEO 2001, but this new development really threw us for a loop," says Tom Gnoske, of the Field Museum's Zoology Department and senior author of the paper.
"However, once we analysed all of the statistical data we found a very strong correlation linking increased age and continued mane development, a significant variable ignored by all previous authors," he added.
Tom said that statistical data indicated that the onset of mane development in lions living below an altitude of 800 meters on or near the equator is delayed, and that the "rate" or speed at which a mane develops in lions from those regions is slower on average than that of the more familiar lions living in the cooler, higher altitudes of the greater Serengeti ecosystem and elevated plains extending northward, such as the Athi/Kapiti Plains and beyond.
He said that in environments like Tsavo that have especially high minimum temperatures throughout the year, lions in their reproductive prime – from the approximate ages of five to seven years old – usually possess only very marginally developed manes, while most of the more thoroughly maned lions in the same territories were already well past their breeding prime.
The researchers also found that manes of lions from all populations continue to develop long after they had achieved sexual maturity.
"Usually lions are well past their breeding prime when they carry the most extensive and often darkest manes of their lives," says Kerbis Peterhans, Adjunct curator of Mammals at The Field Museum, Professor at Roosevelt University, and co-author of the study.
The latest findings are stand in contrast to the recent studies arguing that female-driven sexual selection in the species Panthera leo is focused on males with more extensively developed and darker manes.
"Up until now, it has been incorrectly assumed that lions typically achieve the full extent of mane development by the time they reach four to five years of age," Kerbis Peterhans says.
"This phenomenon carries across the board to all African lion populations, including recently extinct ones, based on the data from our rigorous review of museum specimens," he adds.
The researchers found no evidence that linked rainfall, season, habitat, soil nutrients, nutrition, lion density, prey density or biomass with mane-growth patterns, but established that increased humidity appears to have a negative impact on mane growth in especially warm environments.
The study was completely based on the mane condition of two adjacent populations of wild lions that were separated by only elevation, and thus, climate, and equatorial east Africa was chosen for it because the greatest range of mane variation occurs there.