Our surviving land carnivores are mainly members of the weasel family; the wildcat and the fox are the exceptions. We lost our largest carnivores (wolf, bear and lynx) long ago due to hunting pressure. Four carnivores have full legal protection because they are vulnerable to persecution (otter, pine marten, wild cat and badger) but the other species are still abundant in many areas of Scotland. As with birds of prey, we now know that large carnivores kill their smaller competitors and therefore human management of one species may release the pressure on another. For example, foxes are known to predate pine martens so, in areas where foxes are heavily controlled, the marten population density may increase.
Of all the carnivores, the fox is arguably the most adaptable and can be found in almost every habitat in Scotland. Foxes are mainly active at night but can be seen in daytime where they are not disturbed, in the mid-winter mating period (when foxes are also most vocal) and in the desperate time when they are feeding young cubs.
The basic family unit is a pair but groups of up to six individuals (an adult male and several vixens) may share a territory. This territorial behaviour stabilises the population density by setting a limit on the number of animals in an area. As with other territorial mammals, fox densities are usually higher in the lowlands due to the greater amount of potential prey. Fox dens ('earths') may be actively excavated where the soil type allows, or created from enlarged rabbit warrens. Unlike badgers, bedding is not brought into the den and the cubs are born on bare ground but food is brought back so fur and feathers around the hole indicate foxes are at home and not badgers.
Stoats and weasels
Both the weasel (Mustela nivalis) and the stoat (M. erminea) are widespread and abundant. In Scotland the stoat is the more abundant but both are more numerous than any other Scottish carnivore. Both are routinely controlled by gamekeepers but appear able to maintain healthy populations and have increased since the mid 1990s.
Their size difference affects the range of prey species they can take. Both species habitually enter the tunnels of their prey: weasels are especially well suited to following field and bank voles along their runs and burrows, including tunnels formed beneath snow, whereas stoats are restricted to wider burrows, such as those of rabbits, rats and water voles. Rabbits form the bulk of the stoat's diet and the local distribution and population density of stoats are closely related to those of rabbits. Stoats occasionally den in buildings, although this behaviour seems to be much less common than amongst pine martens.
Polecats and ferrets
The polecat (Mustela putorius) was persecuted to extinction in Scotland by the early 20th Century but subsequent (unofficial) reintroductions have resulted in population becoming established in Argyll and possibly Perthshire. The Argyll population and another in Cumbria provide hope that this species could recolonise the west and south-west of Scotland.
The closely-related feral ferret (M. furo) has been bred in a variety of colours and can interbreed with polecats. Those with polecat-type markings, known as 'polecat-ferrets', can be easily confused with true polecats. As ferrets are widely kept in captivity, escaped animals occur almost anywhere, making it difficult to verify the existence of truly feral (self-sustaining wild) populations. Despite the high number of ferrets lost to the wild each year, feral populations are not obvious on the mainland except in Speyside and Sutherland. But they thrive on offshore islands with numerous rabbits and few other carnivores and are already established on Shetland, the Uists, Benbecula, Bute, and Islay.
The American mink (Neovison vison) became established in the wild in the 1950's as a result of numerous escapes and releases from fur farms. It has now spread throughout most of the country except, as yet, Caithness and most of Sutherland. Colonisation in Scotland has taken longer than elsewhere in Britain and has occurred in the context of a strong, and increasing, otter population. While the overall trend in mink numbers appears to be upward, there is some evidence that the species may be declining in some areas.
Mink are usually associated with aquatic habitats, including coastal areas where the species is particularly abundant. They are present on the Western Isles - where the Hebridean Mink Project is aiming to eradicate them to protect the internationally important populations of ground-nesting birds.
Mink are extremely adaptable opportunist predators and can exploit a wide range of mammals, birds and fish. There is strong evidence that mink are implicated in the drastic decline of water voles in the UK. Mink predation on eggs and chicks at seabird colonies on the west coast and the Western Isles has resulted in widespread breeding failures and a decline in breeding numbers. Mink may also account for a large proportion of salmonid mortality in some river systems.
Last updated on Monday 8th June 2015 at 12:30 PM. Click here to comment on this page