Wolves switched from eating horses to caribou and moose to survive ice age extinction

While other ice age predators succumbed as the climate changed, new research suggests wolves were able to adapt and survive, writes Harry Cockburn

Grey wolves take down a horse on the mammoth-steppe habitat of Beringia during the late Pleistocene (around 25,000 years ago) (Julius Csotonyi)

During the last ice age, which lasted until about 12,000 years ago, grey wolves were just one predator among an array of fearsome beasts, including saber-toothed cats, short-faced bears and cave lions.

But while these animals all died out during the mass extinction at the end of the ice age, the grey wolf prevailed, and can still be found in the tundra, hunting caribou and moose.

New research suggests a major shift in the wolves’ diets could be a key reason why they survived.

The study, led by the Canadian Museum of Nature, shows that wolves adapted their diet over thousands of years with their primary dependence on hunting horses shifting to the caribou and moose they consume today.

The research team analysed the teeth and bones from skulls of both ancient and modern gray wolves from the Yukon region, with the ancient specimens dating from between 50,000 to 26,000 years ago.

“We can study the change in diet by examining wear patterns on the teeth and chemical traces in the wolf bones,” said lead author Zoe Landry of Carleton University in Ontario.

“These can tell us a lot about how the animal ate, and what the animal was eating throughout its life, up until about a few weeks before it died.”

The scientists used existing models which determine what and how animals ate by examining microscopic wear patterns on their teeth.

Scratch marks indicate the wolf would have been consuming flesh, while pits would indicate the animal had been chewing and gnawing on bones as a scavenger.

The analysis of the teeth from ancient and modern wolf skulls showed they both had the scratch marks - suggesting they were active predators across millennia.

To work out what the ancient wolves had been eating, the team examined the ratios of carbon and nitrogen isotopes extracted from collagen in the wolves’ bones.

These relative levels can then be compared with established indicators for specific species.

“The axiom ‘you are what you eat’ comes into play here,” Ms Landry said.

The results showed that horses accounted for about half of the gray wolf diet. These horses went extinct during the Pleistocene - the period of repeated glaciation which lasted from 2.5 million years ago until about 12,000 years ago.

About 15 per cent of the ancient wolf diet came from caribou and Dall’s sheep, with some mammoth mixed in.

The eventual extinction of other large predators - particularly short-faced bears and scimitar cats - could have created more opportunity for the wolves to transition to new prey species, the researchers said.

“This is really a story of ice age survival and adaptation, and the building up of a species towards the modern form in terms of ecological adaptation,” said Dr Grant Zazula, study co-author, and a government of Yukon paleontologist who is an expert on the ice-age animals that populated Beringia.

The team said the study’s findings have implications for conservation today.

“The grey wolves showed flexibility in adapting to a changing climate and a shift in habitat from a steppe ecosystem to boreal forest,” said Canadian Museum of Nature palaeontologist Dr Danielle Fraser.

“And their survival is closely linked to the survival of prey species that they are able to eat.”

Given the reliance of modern grey wolves on caribou, the study’s authors suggested the preservation of caribou populations will be an important factor in maintaining a healthy wolf population.

The research is published in the journal Palaeogeography, Palaeoclimatology, Palaeoecology.