Wolverine - Gulo gulo

by Anders Severson, veterinary student, English program 1st year group 3

Taxonomy:

Wolverines belong to the family Mustelidae and the order Carnivora. Some claims that there are one Eurasian species, Gulo gulo, and an American one called Gulo luscus. But later research indicate that they just are subspieces and that there are only one species in the subfamily Mustelinae.

There has also been research about the phylogenic relationship between genus Gulo and genus Martes (Stone and Cook, 2002, pdf). Researchers examined the nuclear and mitochondrial genes (tissues from heart, spleen or skeletal muscle) from trapped animals they investigated the relationships and time for diverging between the the different genus and also between different species among the Martes. They come to the conclusion, though they suggest additonally research, that the genus Martes may be paraphyletic with respect to the genus Gulo. This would indicate a need to change the taxonomy, putting all the Marten species into the genus Gulo.

 

Physical properties:

Wolverines are the largest member of the weasel family, they have a body length of 65 – 105 cm and a tail length of 17 – 26 cm. The shoulder height is about 40 – 45 cm. They have a weight between 15 and 45 kg. The females are at least 10 % smaller and have a 30 % lesser body weight.

They resembles a large dark badger, but they are dark brown with a lighter brown stripe at each side of the body running from snout to tail. Their fur is dense, large and resist frost very well and is therefor often used by the .

The body is powerful built and got a heavily built head with small ears. The jaws are very strong and can bite through frozen meat and bone. Wolverines got large paws preventing them from sinking down in the snow and making them good swimmers, the paws bears long claws that make them excellent climbers.

Wolverines are very strong and aggressive and is known to have driven away bears, cougars and even packs of wolves from their kills. They can kill animals five times bigger than themselves as a caribou or even a moose. Their best sence is the smell and have also a good hearing but a fairly bad eyesight.

 

Habitat:

Wolverines lives in boreal forests, mountains or open plains and brushlands. In Europe they are only present in Scandinavia and northern Russia. They construct rough beds of grass or leaves in caves or rock crevices, in burrows made by other animals, or under a fallen tree. They occasionally construct their nests under the snow.

Behavior:

Wolverines are solitary animal and defend their territory aggressively against individuals of the same sex. Home ranges can cover 2,000 sq km in winter and they territory are about 200 sq miles. But there are differences in home range size depending on whether it´s a male or female and if the female got a kit or not. Since they are related to the skunks they mark their territory with a strong-scented musk secretion from anal scent gland and urine. The  territory of a male can contain 2 – 3 females, that also get “marked” with secretion and urin. Wolverines usually mark they food to prevent other animals to steal it. They are very shy and tries to avoid contact with humans.

They are terrestrial animals and move with a characteristic loping gallop. Wolverines gallop with great endurance, sometimes moving 10-15 km without rest. They may cover up to 45 km in one day in their activities. When attacking they can reach speeds of over thirty miles/hour

Wolverines are largely nocturnal, but they are often active in daylight. In areas where there are extended times of light or darkness, wolverines may alternate three- to four-hour periods of activity and sleep. Wolverines do not appear to be bothered by snow and are active year-round, even in the most severe weather.

Wolverines are mainly carnivores but can occasionaly eat berries as well. Their diet has a big variety, eggs, rodents, raindeer etc. depending a lot on season and availability.

 

Reproduction:

During the breeding season, may – august, the male stay close to the female but prefers to travel alone. Wolverines are polygynous animals, as indicated by the big differences in size between males and females, and both male and female may remate several times with other individuals. Ovulation is believed to be induced by copulation. After that the females have given birth they hide with their young. The mother defends her territory and intruders are not tolerated. This territorial behavior continues until the young are ready to hunt on their own.

Wolverines are monestrous animals and give birth once every two years. Their pregnancy contains a diapause for 6 months. The whole pregnancy takes 11 months. They usually give birth to 2 – 3 kits, but could give birth to up to 6 kits. The different individuals in a litter could have different fathers. The kits are born in february – march and they are born furry with closed eyes. They nurse for 8 – 10 weeks, are weaned in about 9 – 10 months and reach adult size after 1 year. They may stay with the mother until they are sexually mature, which they are at the age of 2 – 4 years. Wolverines usually don’t live more than 10 years but could in captivity live as long as 17 year.

 

Conservation:

Since the wolverines are suspected of killing livestock, they have been hunted in many areas and have vanished from many of their former territories. In Scandinavia the wolverines are supposed to attack the domestic reindeer. Sometimes they also eat animals already caught in fur traps and will break into cabins and food caches, eating and spraying the contents with its strong scent. Wolverines can even break into canned goods with their sharp canines. Wolverines are supposedly very difficult to trap; when a wolverine finds a trap, it may spring it by turning it upside down or by dropping a stick into it. Wolverines have also been known to carry traps away and bury them deep in the snow.

Besides the hunting for Wolverines, human settlements and low birth rates cooperate in the declining numbers of Wolverines. In United states they have nearly been eliminated and are rare in Canada. In Scandinavia, the estimates are one individual per 200-500 sq km. The estimations are often based on capture and snow tracking data.

In Sweden, the wolverines were placed under the protection of the law 1969.

Other comments:

The wolverines are according to me a fascinating animal which seems to be unknown or forgotten by many people. I hope that protection and understanding between the species can save the wolverines from vanishing totally. Maybe, a bit ironic, will it be the small, economical interest for their fur that actually will save them from extermination.

References:

Http://animaldiversity.ummz.umich.edu/site/accounts/information/Gulo_gulo.html
Http://www.nps.gov/bela/html/wolver.htm
Http://www.blueplanetbiomes.org/wolverine.htm
Http://www.boraszoo.se/om_jarv.htm (In swedish)
Http://www.wolverinefoundation.org/wrlddist.htm
Http://www.wolverinefoundation.org/specacct.htm
Http://www.sou.edu/biology/Faculty/Stone/images/Molecular%20evolution%20of%20martens.pdf