Climate warming makes grey wolves eat more bones, study finds

Grey wolves do not merely alter where they travel as the climate changes. Emerging research indicates that their feeding habits change too.

During warmer phases, wolves seem to eat tougher portions of carcasses, bones included, apparently extracting every possible scrap of nourishment when hunting and feeding conditions become more challenging.

The University of Bristol led the study in collaboration with the Natural History Museum.

Scientists compared wolf teeth from two ancient warm phases with those of present-day wolves in Poland, where winters are becoming milder and snow cover is declining.

They wanted to establish whether warmer climates produce a recognisable signal in wolf diets, and whether this signal can already be detected today.

Reading a grey wolf’s diet through its teeth

The researchers applied a method known as Dental Microwear Texture Analysis (DMTA). As an animal chews, tiny pits and scratches develop across the tooth surface.

These minute marks can reveal what an animal ate during the final weeks or months of its life, an idea sometimes called the “last supper” effect.

To investigate dietary changes linked to climate, the team studied grey wolf molars from three different periods.

One group dated to roughly 200,000 years ago, when summers resembled those of today but winters were colder. A second group came from approximately 125,000 years ago, a warmer interglacial interval marked by hotter summers and milder winters.

The third group comprised modern wolves from Poland, where warmer winters and less snow cover are already being recorded.

The central question was straightforward: are warmer conditions associated with wolves consuming tougher, harder foods?

Fossils reveal a distinct dietary change

On comparing the fossils, the researchers found that the two warm periods showed different dietary patterns.

The tooth wear indicated that wolves from the more recent interglacial consumed harder materials than those from the earlier period.

“The DMTA results from fossil wolves from the two interglacial periods were very different,” explained study co-author Danielle Schreve from University of Bristol.

“Tooth surface features indicate that the dietary behavior 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.”

“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,” Schreve said.

In other words, wolves may still be present, breeding and hunting, while their teeth silently document the pressure they face as feeding becomes more demanding.

When grey wolves begin crunching bones

The overall evidence showed a consistent trend. Wolves in warmer climates ate harder foods, including bones. Researchers refer to this bone-consuming behaviour as durophagy.

“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,” said study lead author Amanda Burtt from Bristol.

“The findings have major implications for wolf conservation across Europe and beyond. Gray 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.”

This directly challenges a widely held assumption. Wolves are renowned for their adaptability, and their populations have recovered in many areas. Yet being adaptable does not necessarily mean being unaffected. It can instead mean coping, and coping may carry costs.

Grey wolves in snowier winters

Warming is especially important because wolves generally do well during cold, snowy winters. Deep snow can leave herbivorous prey more exposed by restricting their access to food and making escape more difficult.

Wolves also travel effectively across snow and ice. Colder conditions are associated with heavier wolves and improved pup survival.

As winters warm and snow cover recedes, this entire relationship changes. Prey animals can move with greater ease, while hunting becomes more difficult.

Wolves may have to expend more energy for the same reward and, after making a kill, may need to make fuller use of it. This aligns with the tooth-wear evidence indicating greater bone consumption.

Put simply, an animal adapted to winter is being pushed towards a world that is less favourable for wolves.

An unusual twist

The study identifies a somewhat uncomfortable point. In Poland, wolves may compensate for some climate-related pressure by hunting deer and wild boar close to farmland, as well as scavenging roadkill.

This is not an ideal conservation outcome, but it could supply calories when natural hunting becomes more expensive.

Paradoxically, wolves living farther from landscapes altered by people may encounter greater future difficulties, as they have fewer alternative food sources available.

In a warming world, the most remote places may not necessarily be the easiest places for wolves to prosper, particularly if prey becomes harder to catch without snow providing an advantage.

Fossil collections and present-day conservation

One of the most striking features of the research is its use of museum fossils as a climate and ecology record rather than as dusty artefacts.

Study co-author Neil Adams, curator of fossil mammals at the Natural History Museum in London, stressed how long certain specimens had been awaiting a question of this kind.

“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.”

What this means for grey wolf conservation

The researchers’ conclusion is not that wolves are doomed. Rather, climate change must be recognised as a genuine pressure on large carnivores, including species commonly regarded as robust and flexible.

If warmer winters push wolves towards hunting that demands more energy and feeding strategies that involve greater risk, this could affect health, reproduction and long-term population stability, especially where human-derived food is unavailable or habitats are fragmented.

The study maintains that long-term conservation planning must account for climate alongside habitat and conflict with people.

Warning signs are not always dramatic population declines. They can be microscopic scratches on a molar that say: life is getting harder, and we’re chewing the bones to prove it.