The color of a giraffe’s brown patches can be used to estimate the animal’s age, a decades-long study of male Thornicroft's giraffes in Zambia, Africa, has found. Drawing from observations recorded by a park ranger in Zambia starting in the 1970s, biologist Fred Bercovitch of the Primate Research Institute and Wildlife Research Centre at Kyoto University, Japan, noted that males’ coats darkened shortly after 7 years of age—turning from brown to black within two years. The change in color, Bercovitch believes, could be due to rising testosterone levels and could be used to signal puberty to other giraffes.
"The main contribution of our work is that we could attach specific ages to coat color changes, which provides something of a 'biomarker' of aging in giraffe," Bercovitch told BBC News. Using a 3-decade record of coat-color changes in wild male giraffes, as well as other lifelong data, Bercovitch estimated that male Thornicroft's giraffes have a maximum lifespan of 22 years in the wild.