Scientists have discovered why wolves look different in different parts of the world

Scientists have studied 227 grey wolf skulls from Europe, Asia and North America. It turns out that skull shape is influenced by climate, latitude, prey type, population isolation and evolutionary history. But there is another factor: humans. Over the last two centuries, hunting, culling, habitat fragmentation and the subsequent recovery of populations have also left a noticeable mark.

In other words, humans have not only altered wolf populations numerically — by removing them from some regions and reintroducing them to others — but have also influenced the physical appearance of different populations.

Details

The study was carried out by researchers from the University of Oulu in Finland, in collaboration with international colleagues and natural history museums. The work has been published in the journal *Diversity and Distributions*.

The team used high-precision 3D scanning and geometric morphometrics — a method that allows the shape of bones to be compared based on a multitude of data points. Put simply, the scientists did not just measure the length of the skull with a ruler, but created a detailed digital map of its shape.

This enabled them to see where the skulls of different populations were wider, narrower, longer or shorter than average. Areas such as the jaws, muscle attachment points and parts of the skull associated with feeding and biting are particularly important.

Why a wolf’s skull can vary

A predator’s skull is not a random structure. It is linked to the type of prey the animal catches, how it bites, which muscles it uses and the conditions in which it lives.

Wolves living in different regions face different challenges. In some places, the prey is larger; in others, smaller. In some places, the climate is harsher; in others, milder. In some places, populations have long been isolated from one another, whilst in others, the animals have been able to move about and interbreed more freely.

Over time, such conditions can be reflected in their anatomy. Therefore, wolves from the Arctic, Scandinavia, Italy, Asia or North America need not be exact copies of one another.

But research shows that natural factors account for only part of the differences.

How humans intervened

Over the past two centuries, wolves have been hunted on a massive scale in many regions of Europe and North America. They were shot, driven out of their usual habitats and deprived of their territory. In some places, populations declined sharply or disappeared entirely.

Later, some populations began to recover. In some places, wolves returned of their own accord, migrating from neighbouring regions. In others, interbreeding with other populations took place. But such dramatic declines in numbers do not pass without leaving a mark.

When a population becomes small and isolated, the flow of genes within it decreases. The animals interbreed less frequently with wolves from other regions. Differences between groups can intensify more rapidly — not only in DNA, but also in physical appearance.

Put simply, humans first severed the links between populations, and then these divisions began to affect the wolves themselves.

What the skulls revealed

The researchers concluded that the current differences between wolf populations are the result of several processes acting simultaneously. Some of the differences can be explained by adaptation to the local environment. Some stem from ancient migration patterns. Some are due to isolation. And some are linked to how humans destroyed, fragmented and then indirectly ‘reassembled’ the populations.

Data from Finland and Scandinavia are particularly significant. In this region, wolves were almost wiped out and subsequently re-established through migration from eastern populations. The study shows that such historical events can leave a lasting mark on morphology — that is, on body shape and bone structure — even after the wolves have returned.

Why this matters

At first glance, the question may seem narrow: so the skulls are different – so what? But for nature conservation, this has practical implications.

If wolves are being reintroduced, returned to regions from which they have disappeared, or used to bolster weakened populations, it is important to understand that not all wolves are interchangeable. Populations may be adapted to different environments, different prey and different survival histories.

If these differences are not taken into account, animals may be relocated to places where they are less well suited to the local conditions. This poses a serious risk to restoration programmes.

The study therefore serves as a reminder that species conservation is not merely a matter of counting numbers. It is vital to preserve the connections between populations, their diversity and their local adaptations.

Background

The grey wolf was once very widely distributed – from Eurasia to North America. But with the expansion of agriculture, hunting and urbanisation, humans began to drive the predator out of many regions.

In the 19th and 20th centuries, wolves were actively culled as a threat to livestock and people. As a result, their numbers fell sharply in many countries. In some regions they disappeared completely, whilst in others they survived in small, isolated groups.

Later, attitudes towards wolves began to change. In many countries, they came under protection, and populations began to recover. But the return of wolves does not mean that history has been wiped clean. If a population has undergone near-extinction, its genetics and physical appearance may bear the marks of this crisis for decades, or even longer.

Separately, the study highlights the value of museum collections. Many of the skulls analysed by the scientists were collected a long time ago. Without such collections, it would be impossible to compare wolves from different regions and understand how populations have changed over time.

Source

Study: Dominika Bujnáková et al., “Global Drivers of Morphological Variation in Grey Wolves”, Diversity and Distributions, 2026.