Why Did Male Mammoths Get Stuck In Traps More Often Than Female Mammoths?

While conducting an analysis of woolly mammoth DNA, European researchers noticed something a little strange. A disproportionate number of male mammoths were found preserved in traps, such as holes and bogs. The explanation, say the researchers, can be be tied to the behaviour of their distant relatives – the modern elephant.

Portion of a mural depicting a herd of mammoths walking near the Somme River (1916) (Image: Charles R. Knight/American Museum of Natural History/Public Domain)

Imagine the scene: It’s about 12,000 years ago during the last Ice Age and a lone woolly mammoth is venturing across a frozen lake. Its finely-tuned ears hears a crack. And then another. The mammoth picks up the pace in hopes of reaching the shore – but it’s too late. The ice collapses under the weight of the massive beast, and it plunges through into the frigid water below. It frantically tries to get out but it’s no use; the mammoth drowns after just a few minutes of struggle.

Chances are, this woolly mammoth was male, according to new research published yesterday in Current Biology.

In the course of analysing mammoth DNA, Swedish Museum of Natural History researchers noticed an odd gender skew. Of the 98 woolly mammoth genomes studied, nearly 70 per cent belonged to males. Since the ratio of males to females was likely balanced a birth, the scientists had to consider other explanations, namely those involving the way these mammoths were preserved after death.

A mammoth tusk found on Wrangel Island. (Image: Patrícia Pečnerová)

The last woolly mammoth to grace this good Earth died around 1650 years ago on Wrangel Island. The relatively recent demise of this species, plus their typically well-preserved frozen remains, means scientists have lots of DNA to work with. But as is typical of palaeontological findings, there’s almost always a selectional effect in play in regards to which remains are discovered and subsequently analysed.

“Most bones, tusks, and teeth from mammoths and other Ice Age animals haven’t survived,” said study co-author Love Dalén in a statement. “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.”

But why should this be the case? Why did more males fall into traps than females?

The explanation, according to the new study, is that inexperienced males travelled alone, and they often got themselves killed by falling into traps that made preservation more likely.

Model at the Royal BC Museum. (Image: Flying Puffin/Wikimedia)

This theory makes a lot of sense when you consider modern elephants – a highly matriarchal species. Modern elephants typically consist of herds of females and young elephants, with young elephants led by an experienced adult female. Males, on the other hand, tend to live alone or among other bachelors, and engage 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,” said Dalén.

This study shows that woolly mammoths were startlingly similar to modern elephants in terms of their behaviour, and that fossil remains can tell us a lot about the social and behavioural aspects of extinct species.

[Current Biology]