Field guide to the most commonly encountered mammals and birds

Here, we provide some basic information regarding commonly observed species (plus some others about which we have had queries).  

Feel free to contact us by email if you have any questions regarding species you have encountered on the site.

For more information about mammals, we recommend the Mammal Society's species hub, here, and MammalNet here. For birds, excellent resources are available from the RSPB (here) and the BTO (here).


Common UK Mammals All UK Mammals Common UK Birds All Species All Deer

American mink

Scientific name: Neovison vison 

Family: Mustelidae

Appearance: Mink are similar in shape to stoats and polecats but are dark brown all over. They are much smaller than otters.

Body length: 60 cm Tail length: up to half of body length.

Weight: 0.5-1.5 kg

Natural history: Mink hunt on riverbanks and in the water, eating mammals, birds, fish and crustaceans. They live in dens near water. Males are highly territorial.

Mink were introduced to the UK for fur farming. Since then, they have become widely invasive. Mink are a major threat to British water voles, because unlike native predators, they are both small enough and good enough swimmers to enter water voles’ waterside burrows. In mainland Europe, they also threaten the critically-endangered European mink.


 (C) tsaiproject (shared under a CC BY 2.0 license)


Scientific name: Meles meles

Family: Mustelidae

Appearance: Distinctive black and white stripes run along badgers’ faces. Their stocky bodies are grey on top with darker undersides.

Height: 25-30 cm Body length: 60-90 cm Tail length: 12-24 cm

Weight: 7-17 kg, heaviest in autumm

Natural history: Common in farmland, woodland and some urban areas, badgers are found throughout Europe and into the Middle East. They are nocturnal, hunting primarily by a strong sense of smell. Badgers have a broad omnivorous diet, including: invertebrates, especially earthworms; fruits, nuts and other plant material; carrion; amphibians; reptiles; and small mammals. Tough hides protect badgers from bee and wasp stings, enabling them to feed from hives.

Badgers live in family groups in underground setts, containing multiple exits, passageways and nesting chambers. Grass, bracken and other plant matter provide bedding for sleeping chambers. Badgers regularly change this lining or “air” it outside the sett for a day, especially while they have young cubs, to reduce parasite abundance. There are rare reports of badgers sharing setts with foxes.

Badgers mate for life, which can last fifteen years. Only the dominant sow in a sett will have cubs; subordinate females help care for the cubs and maintain the nest. Litters typically contain one to five cubs.

At the northernmost parts of their ranges, badgers usually spend winter in hibernation, while in milder climates such as that of southern Britain, they may emerge often from their winter sleep. To prepare, their body mass increases noticeably up to a peak in late autumn. 

 (C) Mark Robinson (shared under a CC BY-NC 2.0 license)

Brown hare

Scientific name: Lepus europaeus 

Family: Leporidae

Appearance: Hares are larger and leaner than rabbits. They have longer legs and longer, black-tipped ears. Their fur is golden-brown. 

Height: 70 cm Weight: 4 kg

Natural history: Brown hares are found in grasslands and woodland edges, where they graze and eat bark. They are very fast runners, reaching top speeds of 70km/h. rather than burrowing, hares typically shelter in depression in the ground called “forms”.

Hares communicate warnings, challenges and interest in each other with thumps of their feet or twitches of their ears. In spring, males are often seen fighting by “boxing” over females.

Changing agricultural practices and shooting have caused hare declines in the UK. As a result, they are a priority species in the UK Biodiversity Action Plan.

 (C) Corine Bliek (shared under a CC BY-NC 2.0 license)

Brown Rat

Scientific name: Rattus norvegicus

Family: Muridae

Appearance: The Brown (Common) Rat is much larger than all mice but is of a similar size to the Water Vole. It has greyish-brown fur and, unlike the Water Vole, a very pointed snout and large ears. Its tail is long, broad and scaly, in comparison the Water Vole has a relatively short tail.

Size: Head and body 21-29 cm; tail 17-23 cm

Natural history: The commonly quoted ‘fact’ that you are never more than six feet from a rat is untrue as it is estimated that less than 1% of buildings contain rats. However, they are extremely adaptable omnivores and can survive in environments not suited to other mammals. Their diet is very wide and they can and will eat anything from grain and seeds to fish, molluscs and birds. Brown rats are active throughout the year and are mainly nocturnal but can be seen during the day where food is abundant. They live in loose colonies and dig their own burrows; home ranges vary considerably depending on food availability.

Females are sexually mature from the age of 3-4 months when they will start to breed producing up to six litters a year. Litter size increases with age with older, larger females giving birth to 11 or more young. The offspring are born blind and hairless but mature quickly and are weaned at around 6 weeks. Young rats are an important food source for a range of predators including owls, polecats, stoats and foxes.

 (C) Sarah Gould (shared under a CC BY-SA 2.0 license)

Fallow deer

Scientific name: Dama dama

Family: Cervidae

Size: Adults males are generally 84 – 94 cm at the shoulder and weigh 46 - 94kg. Adult females are 73 - 91cm at the shoulder and weigh 35 - 56kg. 

Appearance: There are four main variations in coat but many minor variations also exist, including a long-haired version found in Mortimer Forest on the Shropshire / Herefordshire border. The common variety is the familiar tan/fawn colouring with white spotting (becoming long and grey with indistinct spots in winter) on the flanks and white rump patch outlined with a characteristic black horseshoe. The Menil variety is paler, lacks the black-bordered rump and keeps its white spots all year. The Melanistic (black) variety is almost entirely black with no white colouration anywhere. Finally, the white variety can be white to sandy coloured and becomes more white at adulthood. The fallow is the only British deer with palmate antlers. These increase in size with age reaching up to 70cm long when the adult is 3 - 4 years old.

Natural history: Non-native but widely-naturalised. Mostly woodland and open agricultural habitats. 

Behaviour depends upon the environment and population density. In most populations bucks maintain a traditional, defended rutting stand. In others, a temporary rutting stand is maintained to attract sufficient does to herd them into a harem. In areas with very high buck densities a lek (a gathering of males engaging in competitive display to attract potential mates) may be formed. In lower density areas bucks may simply seek out receptive females. In common with other large species of deer, during conflict the bucks’ behaviour escalates from groaning and parallel walks to fighting. During the rut bucks groan tremendously and does with fawns give a short bark when alarmed.

After mating, adult does give birth to a single fawn in June or July after a gestation of 229 days. Bucks generally live for 8 – 10 years although they can live as long as 16 years. 

Fallow deer are active throughout the 24-hour period but make use of open spaces during the hours of darkness in populations experiencing frequent disturbance. Peak activity is at dawn and dusk with most daytime hours spent ‘lying up’, where they lie down to ruminate between feeding bouts. (Source:

 (C) Caroline Johnston (shared under a CC BY-NC-ND 2.0 license)

Grey Squirrel


Scientific Name: Sciurus carolinensis

Family: Sciuridae

Appearance: Larger than the red squirrel, greys are coloured as their name suggests. White individuals are occasionally reported.

Body length: 42-55 cm Tail length: 19-25 cm

Weight: 400-600 g

Natural history: Grey squirrels are invasive in the UK, having been introduced from north America by the Victorians. Populations have spread from southern England and Edinburgh/Glasgow. Grey squirrels carry a parapox virus which they are resistant to, but which is lethal for native red squirrels. Consequently, greys have displaced reds from much of Britain. Grey eradication programs are essential to protect red squirrels at the edges of their ranges.


(C) Jimmy Edmonds (shared under a CC BY-NC-ND 2.0 license)


Scientific name: Muntiacus reevesi

Family: Cervidae

Appearance: Adults males grow to 44 - 52cm at the shoulder and weigh 10 - 18kg. Adult females are 43 - 52cm at the shoulder and weigh 9 - 16kg. Small, stocky and russet brown in colour in summer and grey/brown in winter. Bucks have short (10 cm) antlers growing from long pedicles. Antlers are usually unbranched but a very short brow tine is occasionally found in old bucks. They also have visible upper canines (tusks) suggesting that they are a primitive species. Muntjac have two pairs of large glands on the face. The upper pair are the frontal glands, whilst the lower glands, below the eyes, are called sub-orbitals. Both glands are used to mark territories and boundaries. They have a ginger forehead with pronounced black lines running up the pedicles in bucks, and a dark diamond shape on does. The haunches are higher than the withers giving a hunched appearance. They have a fairly wide tail, which is held erect when disturbed.

Natural history: Non-native but expanding. Mostly forests with a diverse understorey. Breed all year round and the does can conceive again within days of giving birth. Bucks may fight for access to does but remain unusually tolerant of subordinate males within their vicinity. Does are capable of breeding at seven months old. After a gestation period of seven months they give birth to a single kid and are ready to mate again within a few days. Bucks can live up to 16 years and does up to 19 years, but these are exceptional. Muntjac are generally solitary or found in pairs (doe with kid or buck with doe) although pair-bonding does not occur. Bucks defend small exclusive territories against other bucks whereas does' territories overlap with each other and with several bucks. They are known as ‘barking deer’ from the repeated loud bark given under a number of circumstances. An alarmed muntjac may scream whereas maternal does and kids squeak. Muntjac are active throughout the 24-hour period but make more use of open spaces during the hours of darkness in populations subject to frequent disturbance. Peak activity is at dawn and dusk. Long periods are spent ‘lying up’, where the deer lies down to ruminate after feeding. (Source:

 (C) nick ford (shared under a CC BY-NC-ND 2.0 license)

 (C) Airwolfhound (shared under a CC BY-SA 2.0 license)


Scientific Name: Lutra lutra

Family: Mustelidae

Appearance: Otters are one of the largest mustelids, with thick brown fur and webbed feet. Length: 135cm. Weight: 10kg.

Natural history: As they feed on fish, amphibians, waterbirds and crustaceans, otters live close by rivers and lakes in underground burrows called holts. They are very territorial, and mark out their large territories using faeces called spraints. Some otters feed mostly on the coasts, but these individuals need a regular supply of fresh water to clean their fur.

The otter species found in Britain is the Eurasian otter. Many other otter species exist around the world, including specialist sea otters, giant otters reaching nearly two metres long, and clawless species.

Otters declined severely throughout Europe due to pollution of waterways. The most serious impacts of pollution are generally seen in top predators such as otters: the pollution from each contaminated animal they eat builds up in predators’ bodies, accumulating to huge levels. As environmental policies improve, otters are returning to waterways across the UK.

 (C) Peter Trimming (shared under a CC BY-SA 2.0 license)

Pine marten

Scientific name: Martes martes 

Family: Mustelidae

Appearance: Similar in size to a domestic cat, martens are sleek and brown with a cream bib.

Body length: 70 cm Tail length: ~25 cm  Weight: ~1.7 kg

Natural history: Pine martens are highly solitary. They live high in trees, in holes, abandoned squirrel dreys or occasionally in owl boxes. They are omnivores, eating birds, small mammals, invertebrates and fruit.

Martens are rare and elusive in Britain, having been eradicated from most of the UK by habitat degradation and persecution. Recent reports suggest they are beginning to become more abundant in Northumberland and Cumbria. A reintroduction programme is underway in Wales.

 (C) David Little (shared under a CC BY-NC-SA 2.0 license)


Scientific Name: Oryctolagus cuniculus

Family: Leporidae

Appearance: Smaller than hares, rabbits have grey-brown fur, long ears and pale tails.

Body length: 34-50 cm Tail length: 4-8 cm

Weight: 1.1-2.5 kg

Natural history: Rabbits were probably introduced to the UK for food by the Romans. They live in large groups in underground warrens.

Rabbits reproduce very rapidly. The invasive population in Australia increased from 24 introduced individuals in 1859, perhaps to as many as 10 billion by 1920. The disease myxomatosis was introduced to help control them, but has been unable to eradicate these widespread pests there.

 (C) Philip Stephens (shared under a CC BY NC 2.0 license)

Red deer

Scientific name: Cervus elaphus

Family: Cervidae

Appearance: Adults males are 107-137cm at the shoulder and weigh 90-190kg. Adult females reach 107-122cm at the shoulder and weigh 63-120kg. The summer coat is reddish brown to brown and the winter coat is brown to grey. There are no spots on the adult coat. Stags have large, highly branched antlers and the number of branches increases with age. Antlers can have up to 16 points in wild animals. The angle between the brow tine and the main beam is near to 90o degrees.

Natural history: Well distributed in Scotland and patchily so in England. Mostly woodland and forest habitats but also open moor and hill further north. The breeding season, on rut, occurs from the end of September to November. Stags return to the hind's home range and compete for them by engaging in elaborate displays of dominance including roaring, parallel walks and fighting.  Serious injury and death can result from fighting but this only occurs between stags of similar size that cannot assess dominance by any of the other means.  The dominant stag then ensures exclusive mating with the hinds. Despite being sexually mature before their second birthday in productive woodland populations, only stags over five years old tend to mate.  In woodland populations hinds over one year old give birth to a single calf after an eight-month gestation, between mid-May to mid-July. Puberty may be delayed until three years old in hill hinds, which may give birth only once every two or three years. Some Scottish hill populations suffer heavy infant mortality at and shortly after birth and during their first winter. Lifespan can be, exceptionally, up to 18 years. In woodland red deer are largely solitary or occur as mother and calf groups. On open ground, larger single sex groups assemble, only mixing during the rut and in the Highlands of Scotland large groups may persist for most of the year. Red deer are active throughout the 24 hour period but make more use of open spaces during the hours of darkness in populations experiencing frequent disturbance. Peak times of activity are at dawn and dusk. In the Highlands of Scotland red deer use the open hills during the day and descend to lower ground during the night. (Source:

 (C) Philip Stephens (shared under a CC BY-NC-ND 2.0 license)

Red fox

 (C) Philip Stephens (shared under a CC BY-NC-ND 2.0 license)

Scientific Name: Vulpes vulpes

Family: Canidae

Appearance: Red foxes are slender dogs with reddish or russet fur and bushy tails. Their bellies are white.

Height: 35-50 cm Body length: 45-90 cm Tail length: 32-53 cm

Weight: 2.2-14 kg

Natural history: Red foxes are omnivorous, eating plants as well as small animals. They dig underground dens to raise their cubs in, but otherwise often sleep in dense vegetation. Red foxes prefer to hunt at dawn and dusk.

They are widespread throughout Europe, Asia and north America, barring some polar and tropical regions. Red foxes are renowned in folklore for their cunning or trickery. They are highly adaptable creatures, becoming a growing feature of urban areas and surviving in deserts and in high mountains.

Like other dogs, red foxes use their tails, ears and many body gestures to communicate. They use up to twelve different sounds in communication, including greeting and alarm calls.

Trivia:Domesticated red foxes have been bred in Russia. Results from this breeding experiment helped inform a recent theory that a number of genetic changes are common to all domesticated species, and these changes are also seen in all humans.


Red squirrel


Scientific name: Sciurus vulgaris 

Family: Sciuridae

Appearance: These squirrels are reddish-brown, with the red fading somewhat in winter, and white underparts. They have tufted ears and bushy tails.

Size: Body length: 32-44 cm Tail length: 15-20 cm Weight: 250-350 g

Natural history: Red squirrels are forest-dwellers, spending more time in the treetops than greys. Their nests, called dreys, are high-up, in holes in trees or woven from twigs. Red squirrels do not hibernate, but may shelter in a drey for many days in bad weather. They eat nuts, seeds, berries, bark and fungi. Through the autumn, they stockpile nuts to feed on through the winter when other food sources become scarce.

Red squirrels have two litters per year, normally of three or four young called kittens. During bad years for the pine cone crop, squirrels can delay gestation until the following year.

Red squirrels can be right-handed or left-handed, seen in the way they eat pinecones.

A virus carried by invasive grey squirrels has caused serious declines in Britain’s red squirrel population. Red squirrels survive in a continually-shrinking area of northern England, parts of Scotland, and scattered populations protected by the eradication of greys. Many conservation groups are developing programmes to help them reoccupy their natural range, which they readily do when greys are controlled.

 (C) Bob Hall (shared under a CC BY-NC-ND 2.0 license)

Roe Deer

Scientific name: Capreolus capreolus

Family: Cervidae

Appearance: Adults are 60 - 75cm at the shoulder and weigh 10 - 25kg. Males are slightly larger than females. A summer coat of reddish brown turning to grey, pale brown or (occasionally) black in winter. They have a black nose, white chin and white rump patch, and exhibit a bounding gait when alarmed. Males grow short antlers (less than 30cm) which have up to three tines (points) on each. These antlers are shed each Autumn and new ones will begin to grow from November.

Natural history: Widespread in the UK, roe deer are browsers found mainly in woodland and agricultural areas. The rut, or breeding season, occurs between mid-July to mid-August. Bucks become aggressive and maintain exclusive territories around one or more does prior to the rut. Fights between bucks can result in serious injury or death with the winner taking over the loser’s territory or attendant doe. Courtship involves chasing between the buck and doe for some time until the doe is ready to mate. Although mating occurs in this period the fertilised egg does not implant and grow until January. This is thought to be an adaptation to avoid giving birth during harsh northern winters. The gestation period is nine months (four months of no embryonic growth followed by five months of foetal growth) with kids (usually two or three) being born May – June. Initially, young will be left hidden in dense vegetation while the mother goes off to forage, but as they develop they will start to follow their mother around more. Heavy mortality may occur shortly after birth and during the first winter. Roe do not maintain exclusive territories but live within overlapping home ranges. Males mate with several females and females mating with several males has also been observed. Roe deer are solitary, forming small groups in winter. They are active throughout the 24-hour period but make more use of open spaces during the hours of darkness in populations experiencing frequent disturbance. Peak times of activity are at dawn and dusk. Long periods are spent ‘lying up’ where the deer lies down to ruminate between feeding bouts. (Source:

 (C) Philip Stephens (shared under a CC BY-NC 2.0 license)


Scientific name: Mustela erminea

Family: Mustelidae

Appearance: Stoats have a long, thin physique. They are brown with white underparts and a black tip to the tail, which distinguishes them from their smaller relative, the weasel. 

Size: Body length: 17-32 cm Tail length: 6.5-12 cm Weight: 180-250 g

Natural history: Stoats occupy small territories, around 200m by 200m, in farmland, woods and heaths. They are largely carnivorous, and hunt by day or night. Stoats can take prey much larger than themselves, such as rabbits. Being small, they are often prey for hawks, owls and larger mammalian predators.

Especially in the north, stoats’ fur turns white in winter to camouflage them against the snow. This white pelt, known as ermine, was prized in medieval times and worn often by royalty.

Stoats have one litter of six to twelve young each year. Their lifespan is up to ten years, but typically under two.

Stoats have been widely introduced elsewhere in an attempt to control other invasive species such as rabbits. These introduction programmes have typically been disastrous failures: many target regions have never seen mammalian predators before, so naïve native species make easy prey for stoats and native populations have collapsed as a result.

 (C) Rhona Anderson Wildlife & Nature Photography (shared under a CC BY-NC-ND 2.0 license)

Western Hedgehog


Scientific name: Erinaceus europaeus 

Family: Erinaceidae

Appearance: Hedgehogs are brown with spines covering their backs.

Body length: 25 cm Tail length: 2-3 cm

Weight: up to 2 kg

Natural history: Hedgehogs mainly eat invertebrates but have a varied diet that also includes birds’ eggs and amphibians. They are regularly found in gardens, where they eat pests such as slugs. Nonetheless, urban development and habitat loss contribute to their current decline. Hedgehogs are known for curling into balls with their spines facing outwards to protect themselves from predators. However, so many are being killed on roads that they are now losing this trait to better escape cars. Hedgehogs hibernate through the winter. They may wake from hibernation occasionally to find additional food or move nests.

 (C) Giles Watson (shared under a CC BY-NC-ND 2.0 license)

Wood Mouse

Scientific name: Apodemus sylvaticus

Family: Muridae

Appearance: The Wood Mouse is one of Britain’s most abundant mammals. In appearance it is typically mouse-shaped with a long tail, pointed muzzle and large ears. It has dark brown fur with whitish underparts and its eyes are prominent and black. Some animals have a small, isolated, yellowish chest patch. Where present this is always smaller than the yellow neck and chest markings on the Yellow-necked Mouse.

Size:  Head and body 6.1-10.3 cm; tail 7.1-9.5 cm

Natural history: Despite its name the Wood Mouse is not restricted to woodland habitats and may be found in gardens, road verges, hedgerows and arable fields as well as on moorland and heathland. Wood Mice are largely nocturnal and live in burrows underground which have round entrances.  They do not hibernate but may be less active in cold winters when burrows may be shared with others. During the breeding season they are more territorial. Breeding begins in March and runs through until at least October. Females may have four litters a year – or more in favourable conditions. A litter is made up of 4-7 young which are weaned at around 18 days. They feed on a variety of items including seeds, nuts, berries, snails, insects, centipedes and worms.

Image by © Hans Hillewaert /, CC BY-SA 3.0,