The testosterone preserved in the tusks of male woolly mammoths reveals that they underwent a seasonal change called musth, much like modern elephants.
Once they have reached sexual maturity, male African and Asian elephants go through musth for about three months each year. The change is marked by an increase in testosterone and is often accompanied by thick, sticky secretions from the ducts on the temples of elephants. Male elephants are said to be more aggressive and agitated during this time, although the exact relationship between hormonal changes and behavior is unclear.
Woolly Mammoths (Mammuthus primigenius), which disappeared about 4000 years ago, were closely related to Asian elephants. Their tusks, like those of elephants, have grown throughout their lives, and previous studies have recorded hormones such as cortisol, testosterone and progesterone stored in dental tissue called dentin.
Paleontologists have long suspected that woolly mammoths suffer from musth. To test this idea, Michael Cherney at the University of Michigan and his colleagues isolated and analyzed testosterone levels in the tusks of a male African elephant, a male woolly mammoth thought to have lived around 35,000 years ago, and a mammoth woolly female that would have lived around 5,500 years ago. By sampling many sections along a tusk, they were able to see how hormone levels fluctuated over the animals’ lives.
In the elephant, testosterone levels peaked 20 times more during musth than the rest of the year. The tests showed similar fluctuations in the male mammoth, with testosterone reaching 10 times higher than the initial value. There was little variation in testosterone levels in the female mammoth.
“This is such an exciting and fascinating scientific investigation,” says Susan Albert at Duke University in Durham, North Carolina, who was not involved in the study. “Comparing the tusks of elephants and mammoths is compelling evidence that they pick up the same signals in both species.”
Musth was “low hanging fruit” for an initial study, Cherney says, but the new method has the potential to document many aspects of mammoth life, as well as other extinct animals. “We expect to be able to identify pregnancies, maturation ages, stress events and other things that could be used to improve our understanding of mammoth and mastodon paleobiology,” he says.