Last updated December 4, 2017 at 4:48 pm
The overwhelming majority of mammoth remains found across Siberia are male, but why? Swedish scientists speculate that it’s because the young males wandered off from the herd, engaged in risky behaviour and fell into “natural traps”, such as bogs, where they were buried and so protected from the elements.
“Most bones, tusks, and teeth from mammoths and other Ice Age animals haven’t survived,” says Love Dalen of the Swedish Museum of Natural History.
“It is highly likely that the remains that are found in Siberia these days have been preserved because they have been buried, and thus protected from weathering.
“The new findings imply that male mammoths more often died in a way that meant their remains were buried, perhaps by falling through lake ice in winter or getting stuck in bogs.”
The researchers sexed 98 woolly mammoth specimens collected from across Siberia and discovered that 70 per cent of specimens belonged to males. They note that all samples were collected opportunistically and so can be considered a random sample of the available fossil record.
The findings are reported in Current Biology.
The answer may hint at the similarities between woolly mammoths and modern elephants. Elephant herds of females and young elephants are led by an experienced adult female, while male elephants are more likely to live in bachelor groups or alone and engage in risk-taking behaviour.
“Without the benefit of living in a herd led by an experienced female, male mammoths may have had a higher risk of dying in natural traps such as bogs, crevices, and lakes,” Dalen said.
The study’s first author Patrícia Pecnerova, also at the Swedish Museum of Natural History, said she was surprised by the findings. “Since the ratio of females to males was likely balanced at birth, we had to consider explanations that involved better preservation of male remains.”
The researchers are engaged on a wider, longer term study of the woolly mammoth genome. They now plan to see if the same skewed sex ratio exists in other species.
“Assuming that social structure can lead to this type of sex bias in fossil remains, we predict that other Pleistocene fauna that lived in equivalent female-dominated social groups would show a similar pattern,” they write.
“For example, palaeontological sites such as the Rancho La Brea and McKittrick tar pits [both in California] contain various species of megafauna that were accumulated over thousands of years as individuals became trapped in the tar.
“Within the deposits at La Brea, remains from the now-extinct wild horse, Equus occidentalis, follow the predicted pattern and predominantly consist of subadult males.”