WOLVERINE
Class: MAMMALIA
Order: CARNIVORA
Family: MUSTELIDAE
Genus: GULO
Species: GULO
This species of medium-sized carnivore is the largest mustelid that lives primarily on land. It is the only species within its genus; but is believed to be of close relation to the martens; which are tree-dwelling carnivores found both in Eurasia and North America. The wolverine may have diverged from the martens some 8 million years ago. The wolverine’s distribution surrounds the Arctic circle – they are found in Northernmost Eurasia, in the European countries of Norway, Sweden, Finland, and Russia, and as far south as the northern areas of the Rocky Mountains in North America. They are also found in the northernmost areas of the North American continent, including Ellesmere Island – the northernmost island of the Arctic Circle. It is absent from Greenland. It lived in the United Kingdom as well until about 6000 years ago; when it may have been hunted for its meat and pelt. Traditionally there are two sub-species of wolverine – G. g. gulo, of Eurasia, and G. g. luscus of North America. Some scientists believe that those of the Kenai Peninsula are of a unique subspecies, G. g. katschemakensis – but genetic studies have not found significant evidence for this to be the case. The name in English seems to have derived from ‘wolf’ some point in the 16th century; elsewhere it is referred to as the ‘glutton’, or the ‘quickhatch’.
At about 40 centimetres [35-50 centimetres range] at shoulder, and a body length [including tail] of about 70 centimetres [ranging from 60 centimetres to 1 metre], weighing in the region of 10 kilogrammes [again a fairly wide range; males weighing from 11 to 18, and females from 6 to 12], wolverines are a fairly small carnivore for their northern environment; in comparison particularly to brown bears and timber wolves. Wolverines have a rugged coat, with a bushy tail, and are mainly brown are dark grey in colouration, with darker dorsal areas, legs, tail-tip and muzzle. The forehead and area around eyes are lighter in colouration, as is an area of fur around the animal’s chin. The skull of the wolverine is shorter and more rounded than that of the wolf, but still has a bite-force [though again, lesser than that of the wolf] capable of crushing bones, and dispatching animals like caribou. In Eurasia, adult reindeer are rarely seen as prey – but younger reindeer are occasionally seen as such. In some sense, the proportions of the wolverine are more akin to those of bears than of fellow martens, with a more heavyset body plan. They have 38 teeth, its upper molars rotated 90 degrees inward, characteristic of mustelids. They have five toes, which are rather spread-out, allowing the animal to spread out its weight on snow.
The area which is inhabited by wolverines is mainly that of boreal forest. This type of forest is the northernmost on Earth, though also the most widespread. The only trees which are able to sustain themselves in such an environment are those of deciduous and conifers, with a rather low diversity amongst tree species, with soils having acidic qualities, in addition to being low in nitrogen. And so many trees of the Boreal do not have conventional leaves at all – instead having smaller pine needles which need comparatively less resources to sustain. Summers in the Boreal are warm – summers reaching some 21 degrees Celsius – but these are short, with much of the year being that of a long, cold, winter – which can reach such frigid temperatures as -54 degrees. But it is amongst these extremist conifers that wolverines thrive – in Idaho some 70% of wolverine behaviour was recorded in montane coniferous forests. In Alaska, wolverines seem to venture into rocky outcrops during the summer, where it is open, venturing into spruce forests in the winter. It seems that amongst most populations, wolverines assume a more open habitat during the summertime – perhaps for higher availability of prey; or to avoid human intervention. One area where wolverines are most often observed is that of the Glacier National Park in Montana, with some 20 species of tree. The tallest tree in the area may be that of the Western Larch, at almost 50 metres in height. The park itself is a mixed landscape of lakes, valleys, and mountains – as well as glaciers. Such mixed landscape including meadows, rocky outcrops, forests and mountains may well constitute ideal wolverine habitat, especially with the abundance of ground squirrels. Although Montana is sometimes referred to as the ‘Wolverine State’, the animal is now rare in the state, with Glacier providing perhaps a last stronghold. Although they are considered especially powerful for their size, wolverines are wary of human settlement, preferring to stay away. It is possible that in the past wolverines were regulars of lowland habitat, but with the agricultural expansion of the New World, wolverines have become confined to only the most remote locations of their range. Although not regularly done, wolverines can climb trees.
The power of the wolverine has been one largely embellished in natural accounts – some accounts telling how they drive away three pumas at a time, destroying log cabins out of wretched will – but the veracity of many of those accounts is questionable. Those who have worked closely with wolverines in the field find little in the manner of aggressive interactions against larger carnivores, and indeed scavenge more often than larger carnivores. But within such excessive stories appear to be shreds of truth – wolverines are resistant animals, which can wander almost 50 kilometres in one night, often over rugged, mountainous terrain. And wolverines which have been equipped with tracking device have been found to move across steep, icy slopes with impressive speed. Most hunting amongst wolverines takes place during the summer – most of this consisting of ground squirrels such as the hoary marmot, Marmota caligata, and rabbits such as the snowshoe hare, Lepus americanus. In Norway, areas of greater rodent abundance found correlation with higher rates of reproduction. In winter and spring they seem to thrive off scavenging – especially the larger carcasses of caribou or moose. But live ungulates have also been observed as prey items – particularly reindeer calves, which are born in the spring. And it may be the presence of other major predators – lynx and wolves in particular – which fosters healthy wolverine population, giving credence to the idea that wolverines may not be obligate scavengers or predators, but are flexible in how they consume prey items. In times of famine, however, they suffer – with starvation being considered a significant cause of natural death amongst wolverines.
Traditionally viewed as nocturnal, wolverines are not believed to be strictly diurnal or nocturnal – rather activity is fairly even between either hours. Wolverines are largely solitary; albeit polygamous – though the specifics surrounding sexual selection remain largely unknown. Males have the larger home range – up to 675 square kilometres in Alaska [and 1500 square kilometres elsewhere], and females about 200 square kilometres. They are, however, easily detected by a strong odour – which they use to deter other wolverines – or other animals altogether, from stealing their feed. Where the size of female home range is determined by food availability, male home ranges are ultimately determined by availability of mates. In Sweden, a majority of female wolverines have been found consistent to a particular home range over the years – and there it was observed that when several females died off, their close relatives were quick to take over their former home ranges. The breeding season occurs from May until August in Alaska, and June until July in Finland. However, they are not considered pregnant immediately afterwards - as the eggs do not implant until the late winter; or if the wolverine has resources to bear young. If she does not, then the eggs are absorbed. Afterwards, the female only has a short pregnancy of up to about 2 months before giving birth to a litter of up to 5. They are born in a den that is often built into the side of a hill, mound, or ravine. Beneath the snow, the den can be 5 metres in depth. The kits, weighing about 85 grams and birth, are completely white in colouration – only becoming darker in colour as they age. At 6 months old, the kits’ colouration starts getting darker in areas, looking more akin to an adult wolverine. Although they are not social with foreigners, mating pairs have been observed to hunt together – as have small family groups and siblings. Despite a fierce reputation, wolverines often fall prey to larger wolves and bears – and are injured by rival wolverines on occasion as well. If these do not significantly affect an individual, it may live up to 10 years – though animals kept in captivity live almost twice as long.
Amongst larger predators, relatively little is known about wolverines, even amongst scientists – uncommon in both Eurasia and North America. Most data concerning Eurasian Wolverines comes from Norway – which operates a nationwide monitoring programme to produce counts of natal dens. In many Eurasian cultures, the wolverine assumes a role as a trickster – often appearing as central character – and sometimes as a hero. Several cultures, including the Netsilik Inuit and Peel River Kutchin, have eaten wolverine in time of scarcity. The Micmac, whereas, did not hunt the wolverine for food – but rather killed it as a vermin, afterwards using its fur to make clothing. Exaggerated accounts, mainly from trappers of the north-country, spoke of the wolverine as being ‘deomniac’ in character, being the most gluttonous mammal of its size. But, even so, wolverine-inflicted attacks on humans remain vanishingly rare, and deaths at zero. The behaviour of the wolverine is probably not greatly different from that of the pine-martens, except for its large size and terrestrial attitude. The name of the animal would be lent to a character of the X-Men comics – of whom the first major appearance was in 1974. With the X-Men comics remaining of great popularity; it seems that it’s in reference to this character that the word is most popularly used – with one actor of the X-Men movies stating that he was unaware such an animal existed. They are often handled in the field for short periods of time; and have been tamed by people on numerous occasions, having been described as affectionate in a similar manner to dogs.
Wolverines historically have been recorded in California, Utah, Colorado, and the Great Lakes region – but have not been recorded in any such area since 1922, when the last recording came out of California. Populations in the Rocky Mountains and Cascades have been variable over the years; but in more recent times they seem to have re-established there; the Rocky Mountains consituting the only major wolverine habitat south of the Boreal. During and since the 20th century, wolverines have spread across their range, with them appearing in low-elevation areas of Washington during the 1970s, but no evidence of them living there remains. With encroaching architecture leading to destruction of the coniferous forests of northernmost Scandinavia as well as North America, it may be that in the future wolverines will continue to be confined to the most remote areas of their native nations. Despite this, the IUCN considers them of ‘Least Concern’, noting that whilst the population is in decrease, wolverines are of naturally low population density, and it’s unlikely the current rate of decline will be sufficient even to consider the ‘Near Threatened’ status.
The Wenden Animal Encyclopaedia would like to thank especially:
The Wolverine Foundation, at wolverinefoundation.org.