Gray wolves take down a horse on the mammoth steppe habitat of Beringia during the late Pleistocene (about 25,000 years ago). Credit: Julius Csotonyi
Gray wolves are one of the largest predators that survived the extinction at the end of the last ice age, about 11,700 years ago. Today, they can be found in the Yukon’s boreal forest and tundra, with caribou and elk as their main food sources.
A new study led by the Canadian Museum of Nature shows that wolves may have survived by adjusting their diet over thousands of years – from a primary dependence on horses during the Pleistocene, to caribou and elk today. The results are published in the journal Paleogeography, paleoclimatology, paleoecology.
The research team, led by museum paleontologist, dr. Danielle Fraser, and student Zoe Landry, analyzed evidence preserved in teeth and bones from skulls of antiquities (50,000 to 26,000 years ago) and modern gray wolves. All the samples were collected in Yukon, a region that once supported the Beringia mammoth steppe ecosystem, and are compiled in the museum’s national collections as well as those of the Yukon government.
“We can study the change in diet by examining bearing patterns on the teeth and chemical traces in the wolf bones,” says Landry, the lead author who completed the work as a student at Carleton University under the supervision of Fraser. “It can tell us a lot about how the animal ate and what the animal ate throughout its life, until about a few weeks before it died.”
Zoe Landry, lead author of the study, holds a 40,000-year-old gray wolf skull from the Yukon. This was one of the samples analyzed for the research project, which determined the shift in diet over time of gray wolves. Credit: Danielle Fraser © Canadian Museum of Nature
Landry and Fraser rely on established models that can determine an animal’s eating behavior by examining microscopic bearing patterns on its teeth. Scratch marks indicate that the wolf would have devoured meat, while the presence of pits indicates that it should have been chewed and gnawed, probably as a scavenger.
Analysis showed that scratch marks prevailed in the ancient and modern wolf teeth, meaning that the wolves persisted as primary predators and hunted for their prey.
What do the gray wolves eat then? The modern diet – caribou and elk – is well established. The diet of the old wolves was assessed by looking at the ratios of carbon and nitrogen isotopes extracted from collagen in the bones. Relative levels of the isotopes can be compared with established indicators for specific species. “The axiom, you are what you eat, comes into play here,” Landry says.
Close-up of a 40,000-year-old gray wolf skull. This was one of the samples analyzed for the research project, which determined the shift in diet over time of gray wolves. Credit: Danielle Fraser © Canadian Museum of Nature
Results showed that horses, which became extinct during the Pleistocene, make up about half of the gray wolf diet. About 15% came from caribou and Dall’s sheep, mixed in with some mammoths. All this at a time when the old wolves would coexist with other large predators such as scimitar cats and short-faced bears. The eventual extinction of these predators could have created the wolves more likely to move on to new prey species.
“It’s really a story of survival and adaptation of the ice age, and the building of a species to the modern form in terms of ecological adaptation,” says dr. Grant Zazula, co-author of the study, and the government of Yukon paleontologist who is an expert on the ice age animals that populated Beringia.
The findings have implications for conservation today. “The gray wolves have shown flexibility to adapt to a changing climate and a shift in habitat from a steppe ecosystem to boreal forest,” Fraser explains. “And their survival is closely related to the survival of prey species that they can eat.”
Given the dependence of modern gray wolves on caribou, the authors of the study suggest that conserving caribou populations will be an important factor in maintaining a healthy wolf population.
Reference: “Dietary reconstruction and evidence of prey shift in Pleistocene and recent gray wolves (Canis lupus) from the Yukon Territory ”by Zoe Landry, Sora Kim, Robin B. Trayler, Marisa Gilbert, Grant Zazula, John Southon and Danielle Fraser, March 20, 2021, Paleogeography, paleoclimatology, paleoecology.
DOI: 10.1016 / j.palaeo.2021.110368
This study was funded by an NSERC Discovery Grant awarded to Dr. Danielle Fraser. Isotope analysis was done by dr. Sora Kim and dr. Robin Trayler at the University of California, Merced. In total, the research team obtained data from 31 Pleistocene skulls as well as data from 17 modern skulls (most collected in the 1960s). All specimens are in the collections of the Canadian Museum of Nature and the Government of the Yukon.