For Immediate Release The Field Museum, Greg Borzo (312) 665-7106 gborzo@fieldmuseum.org On-going research Whatever the ultimate evolutionary purpose of manelessness, the potential mechanisms are especially intriguing because they might also explain how single male lions are able to control large prides on their own. Both their manelessness and novel social behavior may be related to hormones, the authors suggest. One possibility is that Tsavo lions have elevated testosterone levels. Testosterone is thought to inhibit hair growth and cause balding on the scalp of genetically disposed human males. In addition, it is known to raise levels of aggression and is higher in territorial males than in nonterritorial males. “Tsavo lions are thought to be especially aggressive, and high levels of male hormones may simultaneously underlie this aggression, their unique social system, and manelessness,” Patterson says. To test this theory, Patterson and Kays—together with Dr. Samuel Kasiki of the Kenya Wildlife Service and Dr. Julie Thornton of the University of Bradford in the U.K.—will survey genetic and hormonal attributes of the maneless lions starting this April. The team will be supported by the National Geographic Society and Earthwatch. The scientists will also radio-collar lions on ranches fringing Tsavo to follow their behavior and ecology through an annual cycle. “We hope to gain a better understanding of the developmental mechanism and physiological context of manelessness, as well as the economics of the Tsavo lions’ social system,” Patterson says. Download Images To download a 200 dpi tif image directly to your computer, click on the thumbnail image(s) below. Caption information may be found under "file/file info" of the Adobe® Photoshop® file. Maneless lion File Size= 2.7 mb Print Size = 4"X6" Maned lion File Size= 2.7 mb Print Size = 4"X6"