An international team of researchers led by the Swedish Museum of Natural History has discovered that fossilized remains of woolly mammoths (Mammuthus primigenius) more often came from males than females (69% versus 31%). The scientists speculate that this skewed ratio exists in the fossil record because inexperienced male mammoths more often traveled 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 haven’t survived,” said senior author Dr. 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.”

“Our 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.”

For the study, Dr. Dalen and colleagues generated genomic data from 98 bone, tooth, and tusk samples collected at various locations throughout Siberia.

They then used these data to determine the sex of the mammoth specimens.

“We were very surprised because there was no reason to expect a sex bias in the fossil record,” said first author Dr. Patrícia Pečnerová, 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.”

The findings suggest that woolly mammoths lived similarly to modern elephants, with herds of females and young elephants led by an experienced adult female.

In contrast, the authors suspect that male mammoths, like elephants, more often lived in bachelor groups or alone and engaged in more risk-taking behavior.

“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,” Dr. Dalen said.

The findings are published in the journal Current Biology.

_____

Patrícia Pečnerová et al. Genome-Based Sexing Provides Clues about Behavior and Social Structure in the Woolly Mammoth. Current Biology, published online November 2, 2017; doi: 10.1016/j.cub.2017.09.064