Male woolly mammoths often met disastrous ends: study

Male woolly mammoths were more likely to meet their end in natural traps - falling through thin ice, tumbling into holes or getting stuck in mudflows - than their female counterparts, a study has found.
Researchers from the Swedish Museum of Natural History analysed 98 woolly mammoth specimens collected from various parts of Siberia and discovered that the fossilised remains more often came from males of the species than females.
They speculate that this skewed sex ratio - seven out of every ten specimens examined belonged to males - exists in the fossil record because inexperienced male mammoths more often travelled alone and got themselves killed by falling into natural traps that made their preservation more likely.

"Most bones, tusks, and teeth from mammoths and other Ice Age animals have not survived," said Love Dalen from 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," said Dalen.

"We were very surprised because there was no reason to expect a sex bias in the fossil record," added Patrcia Pecnerova, also from the Swedish Museum of Natural History.

"Since the ratio of females to males was likely balanced at birth, we had to consider explanations that involved better preservation of male remains," said Pecnerova, first author of the study published in the journal Current Biology.
The researchers made the discovery in the midst of a larger, long-term effort to examine the genomes of woolly mammoth populations.
"It became apparent that we were finding an excess of male samples, which we found very interesting," Dalen said.
They decided to sex more samples and to examine the sex ratio of individuals collected from the Siberian mainland and from Wrangel Island.

Overall, they found, males consistently outnumbered females among their samples.
The findings suggest that woolly mammoths lived similarly to modern elephants, with herds of females and young elephants led by an experienced adult female, researchers said.
In contrast, they suspect that male mammoths, like elephants, more often lived in bachelor groups or alone and engaged in more 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.