Why male woolly mammoths dominate the fossil record

Gender bias provides a big clue to the extinct animals’ social behaviour.

Male woolly mammoths appear to have been more than twice as likely as females to get caught and die in natural traps such as bogs, crevices and lakes – the likely result of a matriarchal social structure similar to elephants that led young male mammoths to spend more time wandering alone in unfamiliar territory.

Though researchers don’t know this for a fact, it is advanced as a reasonable explanation as to why the remains of male woolly mammoths have been preserved at a vastly better rate than females.

In a paper published in the journal Current Biology, researchers led by Love Dalen of the Swedish Museum of Natural History in Stockholm report that 69% of 98 sets of woolly mammoth remains collected from various parts of Siberia were male.

This was a surprise, says team member Patricia Pecnerova: there was no reason to expect a gender bias in the fossil record “since the ratio of females to males was likely balanced at birth”. The researchers speculate the bias reflects unusually good preservation, which itself is the result of more males ending their lives after falling into natural traps such as lakes or bogs.

“It is highly likely the remains found in Siberia these days have been preserved because they have been buried, and thus protected from weathering,” Dalen says. “The new findings imply that male mammoths more often died in a way that meant their remains were buried.

“Most bones, tusks, and teeth from mammoths and other Ice Age animals haven’t survived.”

The findings lend support to the view mammoth social structure was like that of modern elephants, with herds of females and juveniles led by an experienced matriarch, while adult males led more solitary lives, wandering further afield with a few other males or alone, increasing their chances of stumbling into trouble.

Without the experience associated with living in a matriarchal family group, or a bachelor group with an experienced bull, young or solitary males might have thus been more prone to die in natural traps, the researchers conclude.