One of our most popular and well loved mammals, the red squirrel Sciurus vulgaris has been a part of the Scottish fauna for thousands of years. It is thought to have arrived in Britain at the end of the last Ice Age, approximately 12,000 – 7,000 years ago, and has been present ever since.
However, the population has not always been stable and red squirrels are reported to have become extinct in some parts of Scotland following large scale deforestation in the 18th century. Populations were supplemented by the introduction of red squirrels from England and, possibly Scandinavia in the late 18th and early 19th centuries.
Scotland now contains the largest continuous population of red squirrels in Britain, supporting 121,000 (75%) of the estimated total of 161,000 animals. However, today’s native red squirrel faces a continued challenge from the North American grey squirrel, Sciurus carolinensis, which was first introduced to Britain in 1876.
To date, the grey squirrel has replaced the red squirrel throughout most of England and Wales, although the native species can still be found in north Cumbria and Northumberland and in small isolated pockets further south. Red squirrels are also found in Northern Ireland, although their range has also contracted noticeably since the introduction of grey squirrels there approximately 50 years ago. In Scotland, the grey squirrel was introduced in three places: Argyll (1892), Fife (1919) and Edinburgh (around 1919). It has since spread south into the Borders and north into Perthshire. Grey squirrels are now widespread in central and southern Scotland with isolated pockets in Aberdeen and Deeside. Their spread is likely to continue.
The red squirrel belongs to the order Rodentia, family Sciuridae. It is one of 27 known tree squirrels worldwide and is well adapted to an arboreal existence, with relatively long hind feet compared to the fore feet. There is no obvious size difference between the sexes, and Scottish red squirrels are generally between 270 to 360 gm in weight.
The colour of the coat can vary markedly from almost black to chestnut or light brown on the back, and pale or cream on the chest and stomach. Squirrels moult their fur twice a year, losing it from head to the tail in the spring, and from the tail forward to the head in autumn.
Winter coats are thicker and generally darker than summer coats, and at this time of year red squirrels display striking ear tufts approximately 2 – 3.5 cm long. Grey squirrels do not have these tufts, which are also small or absent in red squirrels during the summer.
In some red squirrels, ear tufts and tails bleach from winter to summer becoming blond, or even white, from June onwards. It was suggested in the 18th century, that this represented a different subspecies, and was given the name Sciurus vulgaris leucourus. However, subsequent studies of the different forms concluded that this was not, in fact, a separate subspecies but was merely another colour variant.
Red squirrels are found in a range of habitats, from conifer forests to broadleaf woodland, including urban parks and gardens. They can live in mountainous areas up to the tree line, and have been seen at altitudes of 425m near Aberdeen.
Although restricted to woodlands, their use of individual woods depends heavily on the availability oft tree seeds and other food types. They are most abundant in woodlands of Scots pine or of mixed conifers, where they live at average densities of around one squirrel per hectare (2.5 acres). However, they can also survive well in broad leaf woodland, especially those with plentiful hazel nuts, where their population densities are similar to those found in pure conifer woodland.
Although grey squirrels have replaced red squirrels across much of England and Wales (and continue to encroach on the range of red squirrels in Scotland), there are some areas in Scotland where the two species have apparently co-existed for periods in excess of 30 years. This has been attributed to the types of habitat occurring locally, which have sufficient area of conifers to enable red squirrels to survive alongside a grey squirrel population. However, it is not known if this pattern will persist indefinitely.
Grey squirrels by contrast are broadleaf specialists, originating from the oak and hickory forest of eastern North America. They live at much higher densities than red squirrels in these types of woodland with, on average, two to three, but sometimes up to nine, squirrels per hectare. Grey squirrels are able to digest broadleaf seeds, such as acorns, more efficiently than red squirrels, which is thought to be the main reason why they dominate in these areas. However, disease, and habitat loss and fragmentation, may contribute to making areas less suitable for red squirrels to survive.
Red squirrels eat mainly tree seeds, particularly conifer seeds, for most of the year. However, they eat a variety of other foods especially in spring and early summer when the previous autumn’s seed crop may no longer be available. At this time their diet switches to the buds, flowers and shoots of coniferous trees, such as spruce, larch and pine. Other foods include fruits, berries, caterpillars, and even bird eggs.
Fungi, such as species of Boletus and Russula, are also eaten, and red squirrels are even known to place mushrooms in trees to dry them for later consumption. Indeed, squirrels play an important role in forest ecology by dispersing the spores (which survive passage through the gut) of truffle-like fungi which they dig up and consume.
Active throughout the year
Red squirrels do not hibernate but in winter they are active for only a few hours each day, usually at first light, and they remain in their drey during bad weather. In spring their daily activity is extended, reflecting the seasonal increase in daylight and temperature. From May to October they have two active periods in a day, one in the morning and, after a rest period, another in the afternoon.
During the autumn red squirrels spent a lot of time on the ground foraging and storing seeds. Storing food is very important for them and seed stores in pine forests can sustain then for 40 – 50 days. This is sufficient to support them over cold periods or through periods of food shortage.
Squirrel dreys – their nests – consist of an outer shell of twigs and a soft, insulating inner core of mosses, leaves, conifer needles and grass.
Dreys are usually situated near the main trunk of the tree and are supported by branches. Squirrels tend to use more than one drey at any given time and some of these may be used by other squirrels as well. Radio-tracking studies have shown that, during a two-week period, individual squirrels may use as many as eight dreys for resting during the day and sleeping at night, although this is usually restricted to nearer three. Breeding dreys, in which they look after their young, tend to be larger and are lined with soft grass clippings.
Red squirrels become sexually active at about 9 – 10 months of age. The breeding season lasts from around January to September, depending on weather and food availability. There are two peaks of litter production each season, with spring litters produced between February and April, and summer litters between May and September. Not all females breed twice a season and yearling females breed only once in their first year.
Breeding activity in red squirrels is strongly linked to female body condition. Better fed females, in areas with good food supply, give birth to heavier young which in turn are more likely to be weaned successfully.
Mating & birth
Females come on ‘heat’ for only a single day. Males living nearby in the forest are attracted to her, probably by smell, and start following her. As more males join in, scuffles occur which sometimes culminate in the female taking flight. This begins a ‘mating chase’ which is characterised by squirrels crashing noisily around in the trees.
Squirrels do not pair-bond and the successful male will not stay with the female after mating. Males try to mate with more than one female and, occasionally, females will mate with more than one male.
Gestation lasts 36 – 42 days and squirrels can give birth to up to six young in a litter (although the average is three young). They weigh approximately 10 – 15 gm and are born naked, blind and deaf. Hair develops after 8 – 9 days and their eyes and ears open at around 3 to 4 weeks. The young are covered in dense fur by the end of the third week and the tail becomes brush shaped at the end of the fourth week. They begin to explore the nest’s surroundings and feed on solids at 7 – 8 weeks of age. They are generally weaned after 8 – 10 weeks and leave the drey weighing about half their adult weight.
Social organisation in red squirrels depends largely on the distribution of important resources such as food, nest sites and mates.
Neither sex is territorial, that is they do not defend areas of forest against other individuals, except during the breeding season when older females are thought to exclude other females from their nest area. By contrast, male ranges overlap extensively with those of other males and females. This lack of territorial behaviour is thought to be due to the unpredictability of food resources in the habitat. However, they do restrict their daily activity to a measurable area – the home range – which, along with individual spacing behaviour, varies according to sexual activity and the abundance, and quality, of food available.
Parasites and disease
As with most wild-living mammals, red squirrels carry a variety of ticks and fleas. However, although some fleas are common, a species of flea found on red squirrels on the Continent has also been recorded at Pitlochry, Perthshire. It is possible that it arrived in Scotland on red squirrels introduced from Europe in the 19th century.
Red squirrels also carry a species of flea introduced with the grey squirrel. Heavy infestation of fleas and lice can cause problems for red squirrels and can lead to hair loss and balding.
Red squirrels are also known to suffer from a viral infection (parapox virus) which causes symptoms similar to those of myxomatosis in rabbits. The disease is invariably fatal and can lead to local extinctions. Although there have been no confirmed records of the disease in Scotland, the detection of a parapox-like virus in grey squirrels in Hampshire suggests that they may act as carriers of the disease. Consequently there is always a possibility of this disease occurring in Scotland.
Red squirrels are also susceptible to other diseases, most notably coccidiosis, an intestinal parasite which can also be fatal. Such diseases can become especially evident when animals are stressed or under nourished.
Squirrels and People
During medieval times, red squirrels were hunted for their fur which, along with the furs of fox, marten and otter, was used to line cloaks and make warm clothing. Records suggest that skins were actually imported from Flanders to Scotland for this purpose. However, they were also used later in the lady’s fashion industry and, in 1839 alone, over 2,700,000 red squirrel skins were imported to Britain largely to manufacture fur boas (a coil of fur worn around the neck by ladies).
Squirrels can cause significant damage to trees. They do this by stripping the bark to gain access to the sap-bearing tissue beneath. The resulting wounds reduce the value of the timber and make trees more susceptible to disease. Often the bark can be removed right around the main stem (‘ring barking’) and the top of the tree dies as the sap can no longer reach the upper branches. This type of damage can kill trees if it occurs near the base.
Levels of damage are generally related to the thickness and the size, age and species of the tree. Bark-stripping generally occurs between April and July and is more commonly associated with grey squirrels. The exact reasons why squirrels strip bark are unclear. In red squirrels damage tends to occur when there are high densities of squirrels. In grey squirrels, damage levels are also associated with the population density, as well as with the volume and trace nutrient levels of tree sap.
Red squirrel numbers between 1890 and 1910 due to the large scale planting of conifers in Scotland (and elsewhere in Britain) in the late 18th and early 19th centuries (trees between 15 and 40 years old are favoured habitat for red squirrels). In 1903, the Highland Squirrel Club was founded to control red squirrels and over 82,000 animals were killed in the 20 years up until 1933.
Appropriate habitat management is the key to the long-term survival of red squirrels in Scotland. Red squirrels depend heavily on areas dominated by conifers, in contrast to grey squirrels which, to survive, require a high proportion of broadleaved trees. Consequently, habitat management to favour red squirrels should aim for a high proportion of conifers, and should exclude the large-seeded broadleaf specie which favour grey squirrels.
Habitat fragmentation may also make some areas unsuitable for red squirrels, increasing their vulnerability to displacement by the more competitive greys. Grey squirrels can survive in coniferous areas as long as they have access to suitable broadleaf seed supplies, so forest designs which have broadleaf species planted along rides and waterways provide opportunities for grey squirrels to encroach into otherwise inhospitable territory. Large blocks of pure conifers – preferably those exceeding 2,000 hectares – are considered to present the best habitat for red squirrels.
Appropriate forest management is also important to the maintenance of a healthy red squirrel population. Ideally, felling and re-planting programmes should be designated to ensure that a high proportion of trees are always old enough to produce cone crops, which provide a continuous supply of food, and have a closed canopy. Moreover, care should be taken to ensure that, where possible, seed producing areas are left connected by corridors of trees (to enable movement between areas and squirrels.) In areas where red squirrel conservation is a priority, felling should be limited to between October and January when young squirrels are unlikely to be found in dreys.
The red squirrel is included in Scottish Natural Heritage’s Species Action Programme and a variety of research and practical action in underway to conserve red squirrels in Scotland. Red squirrels have also been identified under the UK Biodiversity Action Plan as a species in need of immediate conservation action. A species action plan has been prepared to co-ordinate conservation action in the UK.
Several local groups have been established which enable volunteers to contribute to squirrel conservation. These form a central group – the Scottish Squirrel Group – which helps to co-ordinate action within Scotland. People who wish to get involved should contact their local group, contacts for which can be obtained from SNH. In addition, sightings of squirrels in areas where they are not seen regularly should be passed on to a local record centre, to a local squirrel group or to SNH. Information on areas where red squirrels have been seen regularly in the past have not been noticed recently, are also of importance to the conservation of the species. These records are vital if we are to be able to monitor the changing fortunes of red and grey squirrels and to plan conservation action accordingly.
Squirrels and the Law
This section is intended only as a guide to the law. For further details, please refer to the complete copies of the relevant legislation.
The red squirrel is protected by its inclusion on Schedules 5 and 6 of the Wildlife and Countryside Act 1981. The following provides a brief summary of the provision of this legislation, under which it is an offence to:
Intentionally kill, injure or take any red squirrel
Have possession or control of any red squirrel, or any part of, or anything derived from a red squirrel unless it can be proven that it was obtained lawfully
Damage, destroy, or obstruct access to any structure or place used by a red squirrel for shelter or protection
Disturb a red squirrel while it is occupying a structure or place used for shelter or protection
Sell, offer or expose for sale, or have for the purpose of sale any red squirrel
Publish or cause to be published any advertisement likely to infer that squirrels can, or are intended to be bought or sold.
Use certain indiscriminate methods of taking red squirrels, such as snaring or poisoning
Red squirrels are also protected under the Wild Mammals (Protection) Act 1996 which makes it illegal to subject them to any wilful act of cruelty or abuse.
There is provision within the Act for some activities, that would be illegal, to be carried out under licence. Scottish Natural Heritage and the Scottish Office Agriculture, Environment and Fisheries Department (SOAEFD) share the responsibility of licensing. Purposes for which activities may be licensed under the Wildlife & Countryside Act 1981 include the following:
Grey squirrels are listed on schedule 9 of the Wildlife and Countryside Act 1981. This makes it an offence to release, or allow escape, into the wild any grey squirrel. It is also an offence, by an Order under the Destructive Imported Animals Act 1932, to keep or import grey squirrels except under licence.