Water is made of hydrogen and oxygen, so ratios of rare hydrogen-2 (deuterium) to hydrogen-1, and of rare oxygen-18 to oxygen-16 in tail hair reflect "available drinking water, including river water," Cerling says. "In the dry season, rivers tend to be quite evaporated and have different isotope ratios than in rainy season, when they are flowing."
"The elephants drink the water, and it actually changes the isotope composition of their blood, which is reflected in the isotope composition of their hair," he adds. The hydrogen isotope ratio in elephant tail hair drops when rains fill the rivers, which "shows that abundant water is becoming available at the peak of the birthing season," which also is when vegetation growth peaks, Cerling says.
He says isotope analysis will help researchers understand "how, in the future, wildlife will respond to changes in land use as human population increases and there is increased competition for resources important to elephants grass and water."
The method can be extended "to other regions throughout Africa," says Cerling. "The rest of Africa also is changing land use, and in all parts of Africa where elephants and humans coexist, there is resource competition."
Cerling says the researchers hope to keep monitoring the elephants, including other families, for another 10 to 15 years, which will allow them to "look at how climate and land use change affect the elephants."
|Contact: Lee Siegel|
University of Utah