The study, led by the University of Bristol in collaboration with the Natural History Museum, and published in Ecology Letters has implications for wolf conservation across Europe and beyond.
Researchers compared the teeth of grey wolves from three different time periods using a method known as Dental Microwear Texture Analysis (DMTA).
They examined samples from around 200,000 years ago, a period with summers similar to today but colder winters; from around 125,000 years ago, when summers were warmer than today and winters were milder; and from modern-day wolves in Poland, where winters are becoming warmer and snow cover is declining.
Using DMTA, the team studied microscopic scratches and pits on wolf molars that record the animal's diet in the final weeks or months of its life, sometimes called the 'last supper' effect.
"The DMTA results from fossil wolves from the two interglacial periods were very different," explained co-author Professor Danielle Schreve, Heather Corrie Chair in Environmental Change at the University of Bristol.
"Tooth surface features indicate that the dietary behaviour of wolves from the older interglacial included the consumption of less hard food than those from the younger interglacial period. Wolves during these warmer temperatures appear to have been consuming carcasses more completely," she added.
"The real surprise was that modern wolves from Poland, where climate warming is also ongoing, show the same patterns as those from the younger interglacial, highlighting that they are also experiencing hitherto hidden ecological stress," Professor Schreve said.
The results showed a clear and consistent pattern: wolves living in warmer climates consumed harder foods, including bones of carcasses, a behaviour known as durophagy.
Lead author Dr Amanda Burtt, Honorary Senior Research Associate in Bristol's School of Geographical Sciences, said: "The findings suggest wolves were working harder to extract nutrition during warmer climate periods, scavenging more extensively or consuming parts of prey they would normally avoid.
"The findings have major implications for wolf conservation across Europe and beyond. Grey wolves are often assumed to be resilient to climate change, but this research shows that warming temperatures should be considered a significant factor in conservation planning."
Wolves thrive in cold, snowy winters. Deep snow makes herbivore prey more vulnerable, limiting their prey's access to food and reducing their ability to escape predators. Wolves are also more agile on snow and ice, and colder winters are associated with heavier wolves and higher pup survival.
Warmer winters with less snow cover disrupt this balance, making hunting harder and forcing wolves to compensate through riskier or more energetically costly feeding strategies.
In Poland, wolves are currently able to offset some climate-related stress by hunting deer and wild boar near farmland and by scavenging roadkill. Ironically, wolves living farther from human-modified landscapes may face greater challenges in the future due to limited access to these alternative food sources.
Study co-author Dr Neil Adams, Curator of Fossil Mammals at the Natural History Museum, London, said: "The fossil wolf teeth involved in this project include some that have been part of the national collection for over 175 years.
"Amid the current biodiversity and climate crises, it is more important than ever that fossil specimens in museum collections are leveraged to their full potential in studies like ours focused on conservation palaeobiology. This emerging field seeks to apply knowledge from the fossil record to modern issues of nature conservation and restoration."
The researchers conclude that climate change should be factored into long-term strategies for conserving large carnivores.
The study was funded by the Natural Environment Research Council (NERC) and collaborators included the University of Warsaw, University of Leicester, and the British Geological Survey.
Paper:
'Climate change challenges Grey Wolf resilience: Insights from Dental Microwear' by A. Burtt et al in Ecology Letters
