The wolverine (Gulo gulo) is a solitary powerhouse inhabiting the northern reaches of the globe. This muscular animal has developed a reputation for tenacity that often leads to the misconception that it must be related to bears. Despite its stocky build and formidable presence, the wolverine is not a bear, nor is it a close relative of the Ursidae family. This animal belongs to a completely different branch of the mammalian family tree.
Wolverines: Members of the Mustelid Family
The wolverine is classified as the largest terrestrial member of the family Mustelidae, which is commonly known as the weasel family. This taxonomic group includes a diverse array of animals such as badgers, otters, ferrets, and martens. Mustelids are typically characterized by an elongated body, short limbs, and a flexible spine, a body plan that is less pronounced in the stout wolverine but is a fundamental family trait.
These animals possess specialized anatomical features that distinguish them from bears. Their upper molars are rotated 90 degrees inward, a skeletal characteristic unique to the Mustelidae family. Furthermore, like many of its weasel relatives, the wolverine possesses potent anal scent glands, which it uses aggressively for territorial marking.
The Shared Ancestry Within Carnivora
While wolverines and bears are not closely related, they share an ancient connection as members of the mammalian Order Carnivora. This order encompasses nearly 300 species, including canids (dogs), felids (cats), procyonids (raccoons), and pinnipeds (seals). Both the wolverine’s family, Mustelidae, and the bear family, Ursidae, belong to the suborder Caniformia, grouping them with “dog-like” carnivores.
This shared ancestry means bears and wolverines are distant cousins, having evolved from a common ancestor millions of years ago. Molecular evidence suggests that the main lineages within Caniformia diverged during the Eocene epoch. The Ursidae family separated from other Caniformia around 43 to 38 million years ago, with the Mustelidae family diverging from related groups shortly after.
Physical Traits That Cause Misidentification
The primary reason people often mistake the wolverine for a small bear, sometimes earning it the nickname “skunk bear,” is its superficial physical appearance. The wolverine has a stocky, muscular build with a broad, rounded head and short, nearly hidden ears. Its thick, dark brown to black shaggy coat contributes to a bear-like silhouette, especially when viewed from a distance.
The wolverine’s foot posture also contributes to the confusion. Like bears and humans, the wolverine is semiplantigrade, meaning it walks on the soles of its feet rather than on its toes. This gives it a flat-footed, lumbering gait similar to a small bear. Despite these visual similarities, the wolverine is significantly smaller, weighing only between 20 and 40 pounds, and its body is much lower to the ground and more elongated than any true bear species.