Wolverine Facts and Adaptations
 - Gulo gulo

The wolverine is the largest member of the mustelidae, the weasels, it is stocky, muscular and looks more like a small bear though is the size of a medium dog. It has a reputation for toughness and strength beyond its size being prepared to tackle prey much larger than itself (and tbh they're a bit fed up with the whole x-men thing now).


   wolverine Basics

Wolverine

Average Weight: 9 to 25kg (20-55 lbs)

Average Length:
65 to 107 cm long (26 - 42 inches) plus a tail of 17 - 26 cm (12 inches), 20 to 30cm (6.7 - 10.2 inches), shoulder height 30 - 45 cm (12 - 18 inches). Females are about 30% smaller than males.

Breeding Season: Wolverines are polygamous, successful breeding males form long relationships with two or three females. The breeding season is in the summer though the species practices delayed implantation whereby the embryo is held in a kind of stasis until the time is more appropriate to continue development. Implantation won't take place if food is scarce, the young (kits - typically 3) are born between late February and April. Sexual maturity is reached at two and a half years old, life expectancy is 4-6 years.

Estimated world population: - Wolverines have very large home ranges in the region of 65-200 square kilometers for females and 620 or more for males that overlap the range of several females, so population densities are naturally low. The world population is unknown, the highest numbers are found in Canada and Alaska, probably in the low 10's of thousands, Scandinavian and Russian populations are in the high hundreds or low thousands. The enormous range of wolverines brings them frequently into contact and conflict with people, populations are generally declining and they are becoming endangered in some parts of the range.

Feeding: The wolverine's Latin name Gulo means "glutton" indicative of their feeding style which is an adaptation to potential food scarcity, especially in the winter. They will feed opportunistically on almost any animal food they find, most of their diet consists of carrion, though they will hunt almost any animal they encounter that is smaller or the same size as they are. They will also attack much larger animals such as adult deer, especially if they are weakened or incapacitated by deep snow. They are a very well equipped carnivores with sharp strong claws, powerful jaws and a thick hide. They will defend their food whether they have killed or found it against much larger predators even wolves or bears and successfully take a kill from other predators. In the winter in particular, they will hide excess food away if it is too much to eat in one go so that other carrion eaters won't get it, this is especially important to nursing females.

Conservation status: Least Concern, though with a declining population and increasingly coming into conflict with humans, is likely to be reassessed as more at risk in the future.

Distribution: Circumpolar usually in isolated wooded regions. Females give birth to their young in dens dug into the snow, this tends to restrict them to areas where the snow doesn't melt until late into the spring.

Predators: Wolves and bears. The main predator though is man, wolverine may come into conflict with reindeer herders and sheep farmers, they are also been traditionally hunted for their superior fur.


Arctic fox in winter coat
Distribution range of the Wolverine

  What are Wolverine like? how do they survive?

They survive in some of the coldest places on earth all year round, they have a number of anatomical, behavioural and physiological adaptations that allow them to do this successfully.

Wolverine adaptations:


  • wolverine teeth rotated 90 degreesUnique teeth (anatomical) - The last molars are turned through 90 degrees (shown highlighted in pale blue in the picture of a wolverine skull to the right) which is used for breaking through bone and frozen meat from carrion or a previously secreted cache.

  • Relatively low surface area to volume ratio (anatomical) - Like most cold climate animals, the wolverine has relatively short legs, neck and smaller ears. This means that there is less surface area to lose heat from and makes it easier to stay warm in the cold.

  • Large flat feet (anatomical) - To make it easier to move through deep snow, they act like snow shoes.

  • Fearlessness and fearsome (behavioural) - Tales of the ferocity of wolverine are legion, they have remarkable toughness and tenacity in the face of apparently overwhelming odds, whether defending their own food they have killed or found, or in attempting to take food from another predator. The primary means of killing is suffocation whereby the wolverine grabs the prey by the throat and doesn't let go, the powerful jaws and molars help crush too. There is a record of a wolverine killing a polar bear in this manner. This ferocity is also a wolverines main defence against predators such as wolves and bears.



  • Females are able to delay implantation of the embryo (physiological) - Wolverines mate in the summer and have a short gestation period of about 30-50 days, so delaying the development of embryos means that their birth can be timed more appropriately for the following spring. If conditions are particularly harsh over the winter and the female is not well nourished during what should be the main growth time for her offspring, then implantation can be put off altogether.

  • Females dig a den into a snow bank in order to give birth and protect the young (behavioural) - Wolverines get out of the worst of the cold and the wind in late winter and early spring by digging a den to have their babies. The flip side of this protective environment is that wolverines are dependent on living somewhere there is deep snow quite late on in the season and makes their range susceptible to global warming.

  • Very keen sense of smell (physiological) - Wolverines are able to smell dead animals that have been buried under deep snow by avalanches, an excellent source of food at a potentially very difficult time of the year.

 


Creative Commons Attribution 2.0 license - Left wolverine - Magnus Johansson
Creative Commons Attribution 3.0 license - IUCN - Distribution map
Creative Commons Attribution 4.0 license Top picture Wolverine - William F. Wood