Phil Berry's 33 year of documenting of Thornicroft's giraffes (Giraffa camelopardalis thorncrofti) led to the scientific conclusion that the male giraffe's pattern of brown blotches grows darker with age. The unique set of recordings were started by Phil Berry when he became a park ranger in eastern Zambia's South Luangwa Valley in the 1970s. It is the only place where this sub-species of giraffe can be found. No more than 1,500 remain in the wild, and none are kept in zoos.
(Prof Fred Bercovitch, Primate Research Institute and Wildlife Research Centre, Kyoto University, Japan) >>
The researchers who accessed the 33 years of data analyzed information from 36 male Thornicroft's giraffes, and published their findings in the Journal of Zoology, recently. By comparing recorded colour changes, they were able to generate a life-history profile for the animals. All species of giraffe are known to develop darker coats as they age but the exact timing of the changes were unknown. They found that males' coats first started to change colour at seven to eight years of age and brown blotches transformed to coal-black within two years.Males of the species reach sexual maturity at approximately 10 years, leading Prof Bercovitch to suggest that the initial darkening phase indicates a "coming of age". "I suspect that the blackening of the blotches is a public announcement to the other giraffe that a male is going through puberty - something like adolescent boys flexing their muscles to impress the opposite sex." The authors of the study therefore suggest that the darkening is linked to testosterone upsurges associated with puberty.
The researchers were also able to conclude that the average age of death among male giraffes is about 16 years old, and that the maximum lifespan of male giraffes is about 22 years. Which is considerably shorter than the maximum lifespan of about 28 years for female giraffes.