SHREWS
Shrews are quite common at Bovisand and can often be seen moving their young from nest to nest.
A male shrew is called a boar and a female is a sow; they are highly territorial animals and only socialise with one another in the mating season. Females have three or four litters of 5-7 young between May and September. Females are promiscuous and a litter may have two or three different fathers. Young shrews are occasionally observed following their mother in a ‘caravan’. Each shrew grasps the base of the tail of the preceding shrew so that the mother runs along with a line of young trailing behind. This behaviour is often associated with disturbance of the nest and may also be used to encourage the young to explore their environment.
If you’re lucky enough to see a shrew, you’ll notice that its moves rapidly, with rapid, jerky movements. This isn’t because you scared it; shrews just live life fast and furious.
While this varies among species, a shrew’s heart rate beats 800 to 1000 times per minute. The Etruscan shrew, the smallest terrestrial mammal on earth, has a heart rate that can reach 1500 beats per minute, more than any other mammal and more even than the hummingbird.
There are over 300 species of shrew but the ones on the UK mainland are the Water Shrew (the largest), the Common Shrew, and the Pygmy Shrew
The Water Shrew
As its name suggest, the water shrew is a semi-aquatic species found close to water bodies such as streams, ponds, rivers, reed-beds and fens. They are excellent swimmers, and can often be spotted swimming underwater and diving to depths of 30 to 200cm. Whilst swimming, their fur traps thousands of air bubbles which makes the fur appear silvery and provides important insulation.
The water shrew is the largest of the shrews found in the UK measuring 6 -10cm plus a tail of 4-8cm. It is distinctively jet black on the upper surface, and pale white/silvery on the lower surface, with a very clear demarcation. The fur is often described as velvety with short, dense hairs which are very effective at insulating them against the cold and wet.
They have a long snout, small ears and tiny eyes. Water shrews have relatively large hind feet, but despite spending much time in water their feet are not webbed.
Their teeth often look reddish due to the deposition of iron in the enamel of the tips of the teeth. This is thought to help with reducing wear and tear. They live in burrows and emerge to feed on invertebrates.
They have a short lifespan lasting no more than 19 months. They breed in the summer months producing 2 or 3 litters each with 3-15 young in nest woven from dry grass within a burrow or beneath a log. Their main predators are barn and tawny owls, and occasionally kestrels, foxes and predatory fish. Shrews possess scent glands which produce strong-smelling oily substances which predators such as the domestic cat, find unpleasant.
They feed on prey such as freshwater shrimps, beetles, caddis fly and mayfly larvae; and frogs, newts or small fish. They will also take terrestrial invertebrates such as earthworms and beetles
The Common Shrew
The common shrew is a terrestrial species living almost anywhere and is most commonly found in hedgerows, scrubland, grassland and deciduous woodland. Since shrews must eat every 2-3 hours to survive they are often seen at the surface foraging for food, but live in burrows which may have been used previously by another animal. Shrews do not hibernate, but they do become less active in winter. Remarkably, their size shrinks in winter, so that they require less effort to move and so need less food, not only does the liver shrink but also the brain and the skull.
Shrews have a number of predators and are most commonly killed by tawny owls and barn owls, although weasels, foxes, stoats and kestrels have all been observed as predators. They are often found abandoned by the predator, particularly cats, since a liquid produced from glands on the skin is foul tasting. Shrews are noted for providing a home for a large number of parasites, normally transmitted to the shrew from its prey.
Description: Common shrews are tricoloured: dark brown on the back, pale brown at the sides and whitish underneath, dense velvety fur, with a long pointed nose, tiny eyes, small ears and red teeth.
Size: 48-80mm, tail 24-44mm; tail less than 3/4 length of head and body.
Weight: 5-14g.
Lifespan: In comparison with mice, shrews have a very short life-span and it is uncommon for a shrew to live for more than 12 months.
Diet: Their main food source is insects but they will also eat earthworms, small slugs and snails especially in damp areas.
Shrews have a number of predators and are most commonly killed by cats, tawny owls and barn owls, although weasels, foxes, stoats and kestrels have all been observed as predators. They are often found abandoned by the predator, particularly cats, since a liquid produced from glands on the skin is foul tasting. Shrews are noted for providing a home for a large number of parasites, normally transmitted to the shrew from its prey.
The common shrew is very widespread, the second most numerous British mammal. Living at densities of up to 50 per hectare in many woodlands and often over 20 per hectare in grasslands and other habitats, the most recent estimate puts the number of shrews in Britain at 41,700,000. Although there is no reason to fear their extinction, all shrews (including the common shrew) are protected under Schedule 6 of the Wildlife and Countryside Act (1981). Due to this protection, shrews may not be trapped without a licence and, when trapping for other small mammals, precautions are necessary to minimise the chances of death or damage to shrews.
Pygmy Shrews
Pygmy shrews are one of Britain’s smallest mammals – only pipistrelle bats weigh as little. They have grey-brown fur, paler than that of the common shrew, and a long, slightly hairy tail. Pygmy shrews are active both day and night, but rest frequently. They use a network of runways through the ground vegetation, and unlike common shrews do not dig for prey beneath the soil surface; they are poor burrowers and instead use the burrows and runways of other small mammals. Shrews have energetic metabolisms and pygmy shrews consume one and a quarter times their body weight each day. They are solitary and territorial animals and are aggressive towards other individuals, emitting a high-pitched squeak and sometimes swiping their tail from side to side if they encounter another pygmy shrew.
Mating occurs from April to August and litters up to nine pups (typically 4 – 6) are born between May and October. The young are weaned after about three weeks and become sexually mature the following spring. Females can have 2 – 3 litters each year. The mortality of young pygmy shrews is very high.
Diet: Invertebrates such as beetles, spiders, woodlice and flies. Unlike common shrews, they do not eat earthworms.
Length: 4-6cm. Tail: 3-4.5cm
Weight: 2-6g
Average lifespan: 1 to 1.5 years
GB population 8,600,000. The population trend is unknown. Pygmy shrews are widely distributed throughout Britain and most offshore islands, but they are absent from Shetland, the Scilly Isles and the Channel Islands. They are the only species of shrew to be found in Ireland.
Like other shrews, pygmy shrews are unpalatable to many predators because of an unpleasant smelling secretion from their scent glands. Domestic cats frequently catch and kill shrews but will not eat them. There is no evidence that predators learn to avoid the musky scent however, so it is unlikely to provide much protection for the shrew.