The Elephant's Tail
Photograph courtesy of Thure Cerling
Some foods seem to stick with you forever—on your hips or in your memory. In elephants, evidence of the foods they eat is recorded in their tail hairs, which may be able to help reduce human conflicts with the pachyderms and identify lands important for their survival, according to a study in the Proceedings of the National Academy of Sciences.
“Hair is like a tape recorder of diet,” says lead author Thure Cerling, a geology and geophysics, and biology professor at the University of Utah. “It quantifies the diet changes in elephants in much greater detail than anyone had previously done.”
Researchers collared elephants on the savannahs of Kenya and collected hair from their tails. Each collar was equipped with a GPS unit that sent data to the researchers every hour. Between 2000 and 2006, the scientists collected data on where the elephants migrated and what they ate, discovering that the carbon isotopes in their tails showed which plants they ate during certain times of year.
By observing one herd, named the Royals, the scientists found that in the dry season, the elephants typically eat trees and shrubs, which have a different isotope ratio than grasses. The wet seasons coincides with when the female elephants are trying to gain weight during pregnancy. A couple of weeks after the rains begin to fall the Royals moved to a greener landscape outside of the park where they usually graze. There, grasses usually thrive and provide the elephants with needed nutrition.
In recent years, when the four elephants in the study wandered outside of the park, the grass was too short to eat because of grazing cattle. “Elephants cannot compete for the grass resource when it is continually grazed short as is done by livestock,” says Cerling.
As an increasing number of farmers move into the area, elephants may have less access to the grasses they need. More research could help officials direct conservation efforts that benefit both elephants and farmers.
In the meantime, ecologists can use isotopes to monitor other species in the field without actually monitoring the animals on the ground, which could be helpful when studying elusive wildlife or when conducting research in terrains that are difficult to reach. “This will be a new tool in the ‘toolbox’ of field ecologists,” says Cerling. “At least I hope it will.”