Wolverine - Gulo gulo

The wolverine is a stocky, muscular animal with short legs, and a broad, rounded head. It is the largest of the terrestrial mustelids and it resembles a bear more than other mustelids.

Adult wolverine are roughly the size of a medium dog, with a typical length of 65–87 cm, a tail of 17–26 cm, and a weight of 10–25 kg, although exceptionally large males can weigh over 30 kg. Males up to 30 percent larger than females.

Wolverines have thick, dark, oily fur which is highly water-repellent and resistant to frost. A light silvery facial mask is distinct in some individuals, and prominent white hair patches on the throat or chest also occur.

Wolverine

Wolverines inhabit a variety of habitats in the alpine, tundra, taiga, and boreal forest zones. They are found in coniferous, mixed, and deciduous woodlands, bogs, and open mountain as well as tundra habitats. Snow is generally regarded as an important component of the wolverine's seasonal habitat requirements. Wolverine habitat selection is negatively affected by human activity, including roads, infrastructure, and backcountry recreation.

The wolverine has vast home-ranges, which vary from 100-500 km2 for males and 100-200 km2 for females, and good dispersal abilities. Faecal DNA sampling has detected dispersal distances of more than 500 km.

The species is mostly solitary, which influences the large home ranges and extensive seasonal movements. Wolverines are mainly nocturnal, with some daylight activity, and are considered opportunistic feeders. Wolverines prey on hares, rodents and occasionally animals as large as moose given certain snow conditions. They can also prey heavily on domestic sheep and semi-domesticated reindeer.

Wolverines in Eurasia (specifically, Fennoscandia) are more active hunters than their North American counterparts. This may be because competing predator populations in Eurasia are not as dense, making it more practical for the wolverine to hunt for itself rather than waiting for another species to make a kill and then try to snatch it. They often feed on carcasses left by wolves, so changes in the population of wolves may affect the population of wolverines. Wolverines are also known on occasion to eat plant material.

Wolverines are thought to have evolved to scavenge from the kills of wild ungulates abandoned by other carnivores such as the lynx and wolf, as well prey animals felled by disease or injury. Wolverines also actively hunt smaller animals such as rodents, hares, musk deer, roe deer and wild sheep. Given their dependence on other hunters for much of its scavenged food, wolverines are able to carry and cache large amounts of meat for later consumption.

The wolverine has an average life expectancy of 4 to 6 years in the wild, with a maximum of about 13 years. The species reaches its sexual maturity at 2,5 years and breeding occurs in early spring to late fall with litters of 1-5 young (mean litter size is 3 "kits") born between February and April. The wolverine gestation period is 30–50 days. Successful males will form lifetime relationships with 2-3 females, but females will not produce young if food is too scarce.

Adult wolverines have no natural predators, though they do come into conflict with (and may be killed by) other large predators over territory and food. Juveniles are more vulnerable, and kits have been known on occasion to be taken by predatory birds such as eagles.

Globally, wolverine populations are decreasing, but the species is listed as 'Least Concern' by the IUCN. The European population of Gulo gulo is currently estimated to be approximately 2,260 individuals: 1,400 in European Russia, 150 in Finland, and 326 (±45) individuals in Sweden and 269 (±32) individuals in Norway. The southern Norwegian population was naturally re-established during the late 1970s and was a result of protective legislation.

To the east, the Eastern Russian wolverine population is believed to comprise more than 18,000 individuals. The species is not abundant in Mongolia, but still relatively widespread: it is only found in northern taiga habitats in Hentii and Hövsgöl mountain ranges, northern parts of Hangai Mountain Range and Mongol Altai Mountain Range. The European distribution is connected to the East Russian population along the Urals.

The overall European population forms a relatively continuous distribution with a few geographically and genetically distinct sub-populations and constitutes a small fraction of the larger Eurasian population. The five European sub-populations can be summarised as follows:

The Scandinavian wolverine has shown a low genetic variability and subdivision among populations indicating that the wolverine in Scandinavia has lost variation due to a previous bottleneck. The current population estimate is 580 individuals (>1 yrs of age) with approximately 200 in Norway and 380 in Sweden. The population has a continuous distribution and is narrowly connected to the Finnish – Western Russian. However, an initial genetic analysis has indicated a clear genetic distinction between these populations. In its southern distribution, the Scandinavian wolverine population provides as a source for the Southern Norwegian wolverine population as well as a source for the Swedish forest wolverine population of Southern Sweden.

• The southern Norwegian population was naturally reestablished during the late 1970s and was a result of protective measures. This population has recently increased in numbers and distribution, but is currently kept at around 100 individuals by various control measurements. Genetic surveys have shown that the Southern Norwegian wolverine population is genetically distinct from the Scandinavian population, but the geographic gap between the southern and the main Scandinavian population to the north and east has decreased from 100-200 km in the early 1990s to virtual connectivity by 2006. However, exchange of individuals still is limited and the Southern Norwegian population seems to form a sink with a few individuals emigrating from the northern continuous population.
• The Swedish forest wolverine occurrences were naturally established, during the mid 1990s. These new occurrences were likely established by as few as 2-4 individuals and are currently consisting of 2-10 individuals. Genetic surveys indicate that these occurrences have little, if any, contact with the main Scandinavian wolverine population.
• The Finnish–Western Russian wolverine population has seen an increase in numbers and distribution of wolverines in Finland over the past decades, but decreasing trends in Russia. The western Russian population is estimated to be approximately 1,400 individuals.
• To the west the the Finnish–Western Russian wolverine population is narrowly connected to the Scandinavian population along common borders with Norway and Sweden. An initial genetic analysis has indicated a clear genetic distinction between the Scandinavian population and the wolverines living in northern parts of Finland.
• To the east, the European Russian wolverine population has a wide connection to the much larger East Russian population adjoining along the Urals in western Siberia. The Eastern Russian wolverine population is believed to comprise more than 18,000 individuals.
• The Western Finnish wolverine population was established by translocating animals from domestic reindeer herding areas in the north during the 1980s and 1990s. The population is estimated to consist of about 10-15 individuals and now seems to reproduce naturally. The gap between this and the Northern population is about 200-300 km and little is known about exchange between these populations. This population should therefore be judged as isolated from other populations.

Number of total population and number per country:

• Estonia N/A
• Finland 150
• Mongolia N/A
• Norway 269 (±32)
• Sweden 326 (±45)
• Russia 19,400

• Estonia
• Finland
• Mongolia
• Norway
• Russia
• Sweden

• Altai
• Hardangervidda
• Lena Delta
• Taymyr

During the 19th century, wolverines disappeared from the southernmost parts of their range in Europe (Fennoscandia, the Baltic states and European Russia) mainly due to persecution, but also due to deforestation and other human developments.

The species has a circumpolar distribution, corresponding with the Boreal zone of the northern hemisphere. In Eurasia, the range of the wolverine reaches from Scandinavia through the Russian Federation and Siberia. This range includes territory of the following countries: Estonia, Finland, Mongolia, Norway, the Russian Federation and Sweden.

Based on geographic connectivity and genetic surveys, the wolverines in Europe likely consist of five populations/occurrences.

Wolverine looking what to do

Within the current range, human activities continue to impact on wolverine populations and habitat. The wolverine is threatened by fragmented distributions, presumed low genetic diversity, as well as “population control” hunting and conflicts with human settlements resulting from depredation of livestock. While this species inhabits a zone that is particularly affected by climate change, habitat change or even loss is not taking place at such a rate to be considered a major threat to the wolverine. Ample forested lands and tundra with suitable prey stocks are available throughout much of its range. The problem is the rate of human land use expansion into this range, increasing the frequency of interaction with human populations and conflict over livestock depredation. Given the remoteness of these locations, tolerance of wolverines taking livestock is low and in some areas “population control” hunting is used as a proactive means to avoid loss of animals.

In Norway, where almost 10,000 sheep are believed to be killed by wolverines each summer, government committees have instituted annual harvest quotas in an effort to control livestock losses; however, these quotas may not be sustainable and it is unclear whether this hunt actually reduces the numbers of sheep and semi-domestic deer lost to predators.

While information on northern Asian populations are scarce, the major threats to wolverine populations in Europe can be summarized as follows:

• Scandinavian wolverine population:
  The species is subject to illegal killings due to depredation conflicts (sheep, domestic reindeer). The scope of this is difficult to quantify. Furthermore wolverines are sensitive to human disturbance (settlements, public and private roads etc.) especially in the vicinity of their denning areas.
• Southern Norwegian wolverine population:
  This wolverine population is subject to illegal killings due to depredation conflicts on sheep. The scope of this is difficult to quantify. Most people in Norway are settled in southern Norway and the wolverines are sensitive to human disturbance (settlements, public and private roads, etc.) especially in the vicinity of their denning areas.
• Swedish forest wolverine population/occurrence:
• A high degree of genetic similarity among individuals in the two areas indicates inbreeding, possibly including brother-sister matings. Inbreeding depression and demographic irregularity are therefore likely to be the main threats. These forest dwelling wolverines live outside the distribution of “domestic” reindeer, which form the most common prey for wolverines. Establishment of wolverines in the forest landscape is judged to be a way of reducing conflict with the domestic reindeer industry.
• Finnish–Western Russian wolverine population:
  About half the Finnish wolverine population are living within the reindeer management area in the north, thus creating conflict with the domestic reindeer industry with associated illegal killings. The scope of this is unknown. The Russian economic depression during the 1990s is believed to have led to widespread poaching of ungulate game species. Furthermore, it led to a reduction of the domestic reindeer herding industry due to large losses. This is believed to have indirectly negatively affected the wolverine’s populations in the European part of Russia. The wolverine's main prey base (wild and domestic reindeer) became less abundant and the population has faced a decrease in numbers and distribution during the last few decades. In Russia the wolverine is harvested for fur with no harvest restrictions.
• Finnish western wolverine population:
  It is likely that this small and presumably isolated population will face inbreeding problems as well as being exposed to demographic stochasticity. Inbreeding depression and demographic accidents are therefore main threats. These forest dwelling wolverines live outside the distribution of semi domesticated reindeer, which form the most common prey for wolverines. Establishment of wolverines in the forest landscape is judged to be a way of reducing conflict with the domestic reindeer industry.

• The Wolverine Foundation
  The wolverine (Gulo gulo) earned its place in North American folklore long before north-country trappers and a few over-zealous naturalists began to spin tales of a beast of great ferocity, cunning, and extraordinary strength. Indian mythology describes the wolverine as a trickster-hero, and a link to the spirit world. Still, even today the wolverine remains largely a mystery.
• Finnish Large Carnivore Research Project
  Located in one of the most northern Universities, our research focuses on the ecology, population and conservation genetics of large and medium sized carnivores such as grey wolf, brown bear, lynx, wolverine, red fox and raccoon dog in Finland and Northern Europe. Due to the different background of our group members, we conduct research as well as on other species such as seals and lesser white fronted goose.
• Carnivore Ecology & Conservation
  Here you will find useful resources about carnivores. This includes: permanently updated news, searchable literature database with 17256 papers, 495 full theses to download, future meeting details and proceedings of past ones, action plans, automatic job watch, ecological knowledge monitoring ...

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