MOLES AND SHREWS
Pygmy shrew (Sorex minutus)
Weighing in at less than a 20 pence piece, the pygmy shrew is Britain’s smallest terrestrial mammal. The species is widely distributed and is most commonly found in open areas with rich ground cover, including heathland, moorland, grassland and marshy areas. Unlike other shrew species, pygmy shrews are also found in extreme habitats, including blanket bogs and mountain tops, and have also been found to show a clear preference for stone wall habitats. Despite being widespread, records are scarce and come mainly from cat kills, animals live-trapped during small mammal surveys, and remains found in barn owl pellets.
Pygmy shrews have a pale brown upper coat and greyish-brown underside, lacking the intermediate brown flank colour of the Common Shrew. Their snout is conical and their head is noticeably more domed than that other shrew species. Their tail is relatively long (65-80% of the head and body), and is more obviously dark above and pale below. A bat detector set to 40Hz can sometimes pick up their high-pitched squeaks, which are beyond the hearing range of most people. However, pygmy shrews are far less vocal than the other two shrew species, emitting a single, short, audible ‘chit’ sound when alarmed.
The species has surprisingly specialised teeth, with iron-pigmented ename that strengthens their teeth and allows them to feed on a wide range of invertebrates, including beetles, spiders, harvestmen and woodlice. Pygmy shrews prefer to hunt on the surface rather than underground.
Typical lifespan is around 13 months with most adults dying before winter. Breeding lasts from April to October, with the first young born in May and births peaking in June. Gestation period is marginally longer than that of larger shrew species of at least 25 days. Females may have two or more litters of 4-6 young per year. Both sexes are promiscuous, and males take no part in rearing the young. The young are weaned at 22-25 days.
Pygmy shrews are fairly common and widespread in Somerset. The main threat to the species is predation by birds of prey and carnivores, including domestic cats.
Common shrew (Sorex araneus)
Common shrews are the most frequently recorded shrew species in Britain. Whilst the species forms a major part of barn and tawny owl diets, it seems to be distasteful to many other predators, with uneaten bodies sometimes found along paths.
Common shrews have dark brown upperparts and greyish undersides, with a distinct intermediate brownish flank. They have a proportionately shorter tail (50-60% of the length of their head and body). They are found in most terrestrial habitats where there is thick grass, including shrubs, hedgerow, bracken, deciduous woodland and roadside verges.
The majority of their diet is made up of terrestrial invertebrates such as earthworks, slugs, snails, beetles, spiders and woodlice. They are veracious predator that need to consume up to 90% of their body weight every day. They also tend to catch more prey underground than the other shrew species and will often follow the runs of other mammals and inhabit their burrows.
A particular behavioural trait associated with shrews during early development is ‘caravanning’. Each youngster grabs the base of the tail of proceeding shrew so that the mother runs along with the young trailing in a line behind her. This seems to be initiated by disturbance to the nest, the need to find a new nesting site and orientation.
Common shrews are territorial, with each individual occupying an area of typically 370-630 square metres. When alarmed or angry they produce a succession of piercing staccato squeaks, which are easily detected by the human ear during spring and summer.
The common shrew is widespread in the UK, with an estimated population of 42 million!
Water shrew (Neomys fodiens)
Mostly elusive, the water shrew is equally adept on land as it is in water, where it swims and dives blow the surface. They are noticeably larger in size compared to the common shrew, with a striking darker black uppercoat and a contrasting white belly. Most individuals also have a white tuft behind each ear.
Water shrews are often seen on the banks of flowing freshwater streams and rivers, and in still or slow-flowing water such as ponds, canals, marshes and watercress beds. They typically have a home range along a riverbank of 60-80 metres (up to 500 square metres).
The species is a ferocious predator of aquatic crustaceans and insect larvae, snails, worms, frogs, newts and small fish, and readily dives and forages in water down to a depth of 2m. On land, they feed on a range of invertebrates, including beetles, worms and millipedes. Their venomous saliva allows it to tackle prey larger than itself.
Water shrews generally breed from April to September, having one or two litters of 3-15 young per year. Although they are weaned at 27-28 days, they may remain with their mother for up to 40 days.
Water shrews have a patchy distribution and populations are believed to be declining due to habitat loss, degradation and fragmentation.
Mole (Talpa europaea)
Molehills are a familiar sign of the presence of moles, but the animals themselves are rarely seen alive. Despite a long history of persecution due to to the damage they cause to lawns, gardens and playing fields, the mole is still a common species, including in woodland where its activities are easily overlooked.
The mole has a cylindrical body, covered in dense black velvety fur and a long pink snout. Their large spade-like forelimbs have powerful claws that help them to shift large amounts of earth.
Moles spend almost all their life underground in a system of permanent and semi-permeant tunnels. The familiar molehills are made when earth is pushed up when the mole is re-digging trampled tunnels or when establishing new territories. Earthworms comprise the bulk of their diet, particularly during winter months (90%) but almost any invertebrate can be taken. Moles sometimes disable worms by biting off their heads and storing them for later consumption.
Breeding begins in April, with females giving birth in May and June. A single litter is produced of 3-4 young. Born naked and blind, their fur starts growing at 14 days. Young then disperse at 5-6 weeks, making their way above ground to a new territory.