Despite being common and widespread in England, Wales and, to a lesser extent, Scotland, moles are rarely seen. Instead, their presence is belied by the fruits of their labour, which typically take the form of spoil heaps above their tunnel entrances that we call “molehills”. A pest of gardeners and farmers because of their subterranean activity, moles actually help aerate and loosen soil, which promotes plant growth, and eat many species of invertebrate that are known to damage plants and commercial crops. The soil turned out of their tunnels into the molehill also make excellent potting soil.
That which follows is a summary of mole natural history. The detailed article for this species will follow in due course.
The European mole at a glance
Size and Appearance: Range is 5cm to about 20cm (2 – 8 in.) in length, but average closer to 12cm (5 in.). Weight range 60g to 120g (2 – 4 oz.). Short tail and large spade-like forelimbs for digging; mole ‘swims’ through soil. Tiny eyes (1mm diameter) and ears (small ridges under fur). Fur isn’t ‘slanted’ and so can be brushed forwards or backwards, allowing the mole to move in either direction in tunnel system. Head, feet and tail covered with very sensitive hairs that monitor vibrations and wind disturbance in tunnel system; informs mole of food presence or danger. Internally, mole is well adapted to subterranean lifestyle, including lungs enlarged to fill rib cage and twice erythrocyte (red blood cell) density of other mammals.
Colour: Fur usually velvety dark grey or grey-black, but various colour morphs have been recorded, including white, cream, apricot, tan and piebald animals. A 16cm (6 in.) albino specimen is preserved in a museum in Gers, Midi-Pyrénées (France). Moults three times per year, dependent on latitude.
Distribution and Habitat: Widespread throughout much of Britain and Europe in deciduous woodland, grassland and farmland, although rarely seen. Rare in conifer forests, moorland, flooded fenlands and in agricultural fields that are regularly ploughed (destroys tunnel network, driving moles to field periphery). MoleWatch (2008) data suggest they’re reasonably widespread in England, although there are notable absences around some major conurbations (e.g. London and parts of Thames Valley). Absent from Ireland and, although present in Scotland, there are few data to confirm distribution. Distribution extends from Britain east into central Russia, north to southern Sweden and Norway, south into northern Spain, northern Italy and much or the Ukraine. They are apparently absent from most of Spain, Portugal, most of Italy, Greece and the southern Ukraine.
Longevity: Typically less than a year, although up to three years known in wild. Six years is captive record.
Sexing: Males often larger than females, although not by much (average male is only approx. 5% larger). Sexual separation often requires dissection owing to both sexes having very similar-looking genitalia (difference in size to the order of a millimetre), although the distance between the openings can be used to separate sexes outside breeding season, with practice.
Activity: Spends most of life underground, where it patrols tunnels roughly every four hours looking for food and intruders. Spend more time above ground in summer, looking for food, bedding and females. May move above ground when searching for a territory – surprisingly quick above ground. Active throughout year; more so during breeding season. Most active during the night, although diurnal activity common. Triphasic activity patterns (with three activity periods, each ~ 4 hours, per 24 hrs); two periods during breeding season as males search for mates. Territory defence and tunnel extension accounts for just over 50% activity. Females most active when suckling young. No apparent ability to store fat, so cannot hibernate during winter.
Dens: Lives in a network of tunnels, which it expands throughout its life (at up to 20m / 66ft per day). Displaced earth is pushed to the surface, creating ‘mole hills’. Mole hills serve to direct airflow into the tunnel system, ensuring there is a steady breeze throughout the network even on calm days above ground (helps transfer smell of food in tunnels to mole). Large chambers off the main tunnels are lined with vegetation and used as resting sites. Estimated that mole may move 6kg (13 lbs.) of earth per 20 minutes while excavating tunnels. Fortresses (network of tunnels) may be built over nests, esp. in winter, and may act to conserve heat. Tunnel systems may extend beyond 1m (3.5ft) down.
Territory: Highly territorial and tolerate others only during the breeding season. Males holder larger (often twice size) territories than females. Core areas defended vigorously, but some overlap in peripheral tunnels; aggression reduced by different time use of tunnels. Size and shape of territory highly variable and dependent upon prey availability; average male territory in summer is 3,000 m2 (0.75 acre) cf. nearly 8,000 m2 (2 acres) in winter – females stable throughout year, ranging from 1,300 to 2,100 m2 (0.5 acre).
Diet: Predominantly earthworms (90% in winter, 50% in summer), will opportunistically take insects (e.g. centipedes, millipedes and larvae) and molluscs. There are records of them preying on small rodents — mice and shrews — as well as snakes and lizards, small birds, frogs and other moles – probably feeding on carrion. Some suggestion that their saliva is toxic and used to paralyze worms that are later cached (common in spring and autumn); one cache contained >1,500 worms. Excess earth removed from prey by pulling it through claws. Very fast metabolism requires it to eat at least every 6 hours; eats 40-50g (~ 1.5 oz.), or ~25 worms, per day . Hunt in tunnels, which act as food trap (invertebrates fall in). Apparently rarely eat vegetables, although study from Berlin found Ascomycota truffles in stomachs of 30% of moles caught in pine forest. Hunts using touch from vibrissae on nose, tail and feet. Snout covered in thousands of tiny touch-receptors called Eimer’s organs (named after German zoologist Thomas Eimer who described them in 1871) that are very heavily innervated (~5,000 organs on nose associated with ~105,000 nerve fibres). Can apparently smell earthworms through ~8cm (3 in.) of clay.
Reproduction: Promiscuous with a brief breeding season (March to May) and oestrous (est. less than 24 hours). Male enters female’s tunnels and mates with her. Young born from April to June, after a 30 day gestation. Female digs and lines nest chamber; typically use one, but may have three-or-more and move young if disturbed. The average litter size is four young, but the range is two to seven. Fur growth is complete by 14 days old and start to leave the nest at about one month old; weaned at 4-5 weeks, independent by 6 weeks and sexually mature at about 10 months. Female-only parental care.
Behaviour and Sociality: Solitary outside of breeding season. Make various noises, including squeaks, purrs and shrill twittering, which are presumably used for communication. Wide range of scent glands that transmit information about individuals; secretions crucial for territorial defence. Vacant territories often filled within 24 hours.
Threats: Often killed by predators, but apparently distasteful and so frequently left uneaten. Predators include birds of prey (tawny owls and buzzards), herons, stoats, weasels and foxes; some taken by domestic cats and dogs. Tooth wear, and subsequent starvation, one of major causes of death. No longer widely hunted for pelts, although commonly killed as garden/agricultural pests, particularly on livestock farms where stepping into molehills can result in horses or cattle breaking legs. Not considered endangered, although uncertain of numbers – old estimates put UK population at around 31 million, but this is unlikely still to be accurate.
Benefits: Consume many species that gardeners consider pests and excavated soil makes good compost. Evidence from Swiss Alps that moles may aid the colonization and spread of Water voles (Arvicola terrestris) in grassland habitats.
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