Mustelids in Europe

Want to know some facts about European badger (Meles meles) and Eurasian otter (Lutra lutra)?

Since early times, mustelids have played an important role in human economies and culture. They also appear in some local folklore and legends which characteristics of strength, ferocity, and courage. The mustelid family also has a couple of very charismatic species. For example, European otters (Lutra lutra) are a joy to watch swimming and playing around their aquatic environment. But the mustelid family is much more than just otters, think about the European badgers (Meles meles) in their search for earthworms. In this article, you will learn more about the mustelid family and some of their characteristics. As an addition to this article, I made an ID-sheet about how to distinguish the mustelid species.

Systematics

The family of the Mustelidae (weasels and relatives) is a large group consisting of different species with a variety of environmental requirements. It is even the largest family within the order of Carnivora. The further diversion into subfamilies is rather though nowadays. It’s still debateable, but there are 8 subfamilies accepted. Around the globe, they have found at least 57 mustelid species (weasels, martens, polecats, badgers, and otters). In Europe, 12 mustelid species can be found.

Characteristics

Mustelids are small to medium-sized carnivores. The smallest mustelid is the Least Weasel with only 25g. It’s an inhabitant of Europe and North America. On the other hand, the Sea Otter is the largest mustelid reaching up to 45 kg. The largest of the mustelid family in Europe, and also from the terrestrial mustelids, is the Wolverine, which can weigh up to 18 kg.

Mustelids can be found in a lot of different environments, ranging from oceans, rivers, temperate forests, tropical forest, dry open woodlands, tundra, steppe, and grasslands. Some species are even adapted to our human settlements. For example, Stone Martens are quite frequently seen in some European villages and cities. They are known to use buildings and other human structures as dens. Eurasian Otters are usually found in rivers, but they also can inhabit coastlines and swim in the sea. This is common around Applecross and the Isle of Sky, but also in other locations.

Most mustelids are characterized by a long slender body, short limbs, and a long tail. Badgers and Wolverine are a bit different in that perspective. Furthermore, Sexual size dimorphism is present in the mustelid family. Males can often reach twice the size of the female. It is still unclear why, but the ability to feed on different prey is one option. Weasels and Polecats have long tubular bodies that allow them to hunt in the burrows of rodents and lagomorphs. 

Some species undergo a complete change in coat colour from summer (brownish back) to winter (completely white). In Europe, it’s the (Least) Weasel and the Stoat/Ermine. This change only occurs only in the northern part of their range or at high elevations. Check further with difference weasel vs stoat

From a morphological point of view, mustelids have feet with 5 digits and strong non-retractable claws. Their skull is very long with a low braincase. Most species have a large sagittal crest (ridge on top of the skull) to support the attachment of the jaw muscles. The more arboreal species have a long tail for balancing, whereas the more aquatic species (otters & minks) have partially or fully webbed feet.

Communication

The three main ways of communication in mustelids are visual, vocal, and olfactory. Mustelids are mostly solitary animals. The main way of communication is scent marking. These olfactory signals have the advantage of working in the dark and can last for at least a couple of days. The scent markings can include a lot of different signals with information about territory and mating, and also could contain information about sex, breeding condition, and other characteristics of the individual. Badgers, for example, can stand on their front legs to mark trees, or shrubs higher up. This way of communicating by scent marks decreases the chance of physical encounters and potential fights.

Mustelids are primarily using the secretions from anal and sub-caudal glands and each species is capable of producing its own unique smell. Apparently, the Eurasian Otter has nearly 100 compounds in their scent, consisting of proteins, mucopolysaccharides, and lipids. These compounds are released during defecation, at latrines, or well establish territory marks (like stationary objects). Eurasian Otters can discriminate between the spraints of different individuals. Mustelids can also use their smell to deter an attacker, as it can give an unpleasant odour

Badgers, on the other hand, even scent-mark on other individuals of their group (also common in other social organised mustelid species). This, so called allomarking, gives individuals of the same group a similar odour, allowing them to recognize each other, even in the dark. When away from their set, they often sniff each other’s flanks and rumps. Sometimes two individuals back into each other with a raised tail (mutual squat-marking). All the Badgers in a clan squat-mark each other, but it’s not done equally. The more dominant individuals make more social marks. So, all members of the clan have a mixture of secretions with more of the odour of the dominant individuals.

Learn more about Mustelids. This book gives more insights in evolution, diseasis, social communication, and management. Biology and Conservation of Musteloids is part a very good series, with previous topics on Wild Felids and Wild Canids.

Besides the olfactory communication, during close encounters visual and vocal signals are used. Most mustelids have well-marked facial masks or stripes, which may play a role in visual communication. Usually, mustelids keep quiet. The more social members, such as the otters, can be more vocal at times.

Reproduction

Some mustelid species have a delayed implantation. This means in order to get the birth of offspring in spring, the mating season should be in winter. Winter is usually a hard time for surviving, even without the task of searching for a mate. As a result, in some species mating season has moved backwards to late autumn, which is a more favourable time. Most mustelids have one litter per year, although the weasel has been recorded to get up to three litters in one year. Mustelid offspring are born at an early stage of development, mostly naked with closed eyes. Therefore, the female need to find a very protected burrow or cavity (in a tree). The female will possibly move her offspring regularly, in order to decrease the chance of predation.

Feeding

Mustelids have a limited gut capacity and a demanding metabolism. In general, mustelids are active during the night, although their specific metabolism might need them to be active during the day. Most mustelids are carnivorous, although some are omnivorous. The small weasels are formidable predators and are even capable of killing prey much larger than themselves. The diet of Martens consists of small mammal, insects, and fruits/nuts, and has more variation throughout the year.

Mustela and Martes mustelids are solitary hunters. In general, they kill their prey with a bite in the neck or head area, which usually crushes the back of the skull. The most impressive hunt is this from the Weasel attacking a larger prey… In the video below you can see how a stoat is taking down a rabbit (BBC life)

 

The largest among the mustelids, the Wolverine, is mostly feeding on carrion either killed by large predators (wolves) or died from natural causes. When attacking reindeer, the Wolverine jumps on the back and tries to kill it with bites to the neck or throat. They have an advantage in deep snow. Once a Wolverine has found a carcass, they will stay around the carcass until all edible parts or gone or another scavenger, like a bear, has scared it away.
As a result of a decrease in main prey activity during winter, badgers may have a period of inactivity during the winter (hibernation). For example, the European Badger is in some places primarily feeding on earworms, which are difficult to reach when the ground is frozen etc. … Badgers adapt by decreasing their metabolism and body temperature, in combination with long periods of sleep. Most other mustelids stay active during the whole year.

Ecological role

Mustelids are often seen as keystone species. In Europe, they often are even one of the top predators in areas where wolf, bear and lynx are absent. They can have important roles in maintaining ecosystems. For example, in Scotland and Wales, Pine martens tent to prey more on the larger, invasive, grey squirrel, which is in favour of our native red squirrel.

Threats & Humans

While (in the past) some species were/are seen as a pest species, most of the small mustelids prey on mice, voles, and rats, and by doing so could be beneficial to humans. Mustelids usually have a secret lifestyle and small size, they often stay unnoticed for a long time. Most of the time, they also don’t cause any trouble towards people.

Sometimes, the larger mustelids can cause problems related to humans. For example, the beech marten in Europe is sleeping under the hood of cars, and sometimes biting on the wires. This can lead to cars that are not starting etc. Additional to that, some of the Martens are also killing domestic animals, like rabbits and poultry. Although it’s not happening that often, also surplus killing can happen where the individuals kills almost all the domestic animals in one go, which is obviously not so pleasant for the owner. Otters are known to predate on fish farms, as it’s an easy way to get food.

On the other hand, mustelids have been, and some still are, trained for hunting. For example, Ferrets (probably a domesticated form of the European Polecat) are used to hunt rabbits in some parts of Europe. Some otter species are trained to catch fish and bring it to trainer

The fur industry has been one of the main threats to mustelids. Nowadays it has become more of a luxury item. But in the past, the fur industry has been responsible for the 1 mustelid species that went extinct in the past centuries. The Sea Mink was intensively hunted for fur. It occurred along the coasts of eastern Canada and north-east USA. It was last spotted in 1894. Escaped American Minks have established wild populations throughout Europe and Asia. Introduction of species outside their natural distribution can have a negative effect on native species. Here, the American Mink competes with the European Mink and probably has contributed to its decline. Non-fertile crossings between male American Mink and female European Minks prevent European mink from successfully reproducing. Additional to this problem between closely related species, American Mink has also caused a decline in Water Vole populations in Britain.

Further away from Europe, but a lesson we all should acknowledge: back in the 1880s, New Zealand deliberately introduced Ermine/Stoat and Weasel to control Eurasian Rabbits. This had a huge impact on the smaller mammal and flightless bird populations, as they were easier prey to catch…

Very few people in Europe also participate in so called “badger baiting”, which is only for amusement. A badger is caught and put into a pit with dogs and it simply has to fight for its life. Luckily, it’s not that common anymore.

Some mustelids are involved in the transmit diseases. Mostly a problem in Great Britain and Ireland, but badgers are blamed to play a role in the transmission of bovine TB (tuberculosis). Although there is still no scientific proof that badgers can infect cattle with bovine TB (but there are a couple of indices though), after the 1970s, a lot of actions have been taking against the Eurasian Badgers.

Status and Conservation

As mentioned before, the Sea Mink is the only species of the mustelid family to go extinct recently (around 1894). But caution is needed, as there are a lot of species threatened and high on the endangered list. There is quite some attention going to the Black-footed Ferret in the USA. The European Mink is also one of the more threatened mustelids, occurring only in fragmented places in Europe. Caution is needed when treating invasive species. For example, in France, secondary poisoning of European Mink has occurred as a result of efforts to control Coypu (Myocastor coypus).

Like most species with the need for a decent space, habitat loss and habitat fragmentation have an impact on mostly forest dependent mustelids. Definitely, from climate change perspective, forested corridors need to be preserved in order to allow gene flow among disparate populations

The more aquatic species, like otter and mink, can be heavily affected by water pollution. It can affect their prey, reproductive success, lifespan, etc. Pollution can come from different activities: agriculture (pesticide and fertilizer runoffs), industrial processes (chemicals), urban areas (sewage)

Many mustelids have never been studied properly in the wild. For some species, there is a lack of sufficient data on for example distribution, ecological requirements, social structure, dispersal patterns, feeding ecology, breeding ecology, etc.

As an addition to this article, I made an ID-sheet about how to distinguish the mustelid species.

Learn more about Mustelids. This book gives more insights in evolution, diseasis, social communication, and management. Biology and Conservation of Musteloids is part a very good series, with previous topics on Wild Felids and Wild Canids.

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