Shrews: Seen one minute, gone the next

A FEW days ago, while opening my garden gate, I was amazed to see a shrew scuttling as fast as its little legs could carry it along the lane adjoining my Somerset home. Twitching its whiskered snout as it ran, it quickly disappeared into the hedgerow’s undergrowth.

This is the first shrew that I have seen for many a year and is probably the result of a local farmer’s decision to plant hundreds of tree saplings in his field and allow that field to become a natural meadow. In the fullness of time, this will become a magnificent deciduous woodland but sadly I shall not be alive to see this. In the meantime, the grasses in the meadow are already a metre tall and thus provide an ideal habitat for shrews.

This week, I shall focus on three shrew types: the Eurasian or common shrew (Sorex araneus), the Asian house shrew (Suncus murinus), and the so-called common tree shrew (Tupaia glis), which is of a different family, the Tupaiidae, unlike the two previously mentioned of the family Soricidae.

There are nearly 390 known species of shrew worldwide, and probably the largest population of any animal family with an estimated 100 billion shrews living in our world!

Eurasian or common shrew

There are five species of this restless, insect-eating mammal found in the British Isles. Whilst mouse-like in appearance, it is not a relative of the mouse family and is distinguished by its needle-like teeth and long twitching snout.

Active by both day and night, it never hibernates for it has an unusually high metabolic rate eating as much as 50 to 200 per cent of its bodyweight in its daily food. This shrew lives in thick ground cover in woods and grassland, tunnelling in undergrowth and leaf litter.

Breeding: Shrews live solitary lives only coming together to breed. Mating takes place between early spring and late summer and up to five litters of seven to eight young may be born during that period. The breeding nest is a ball of woven grass, and the gestation period varies from 17 to 30 days.

The mother suckles the young for the first three or four weeks after which they are left to fend for themselves. The lifespan of this shrew species is about 12 to 20 months.

Asian house shrew

Found as a native species of shrew throughout the Indian subcontinent and extending throughout Southeast Asia from southern Thailand to southern China, it has a short, dense mid-grey to brownish fur with a thick tail narrowing at its tip, short legs, and five clawed toes. Its elongated snout distinguishes it from a mouse for it has smaller ears and emits a very strong musk odour from its scent glands.

It is by far the largest of the shrew family at 15cm in length and weighs about 100gm.

During the day, it hides in its burrow or in human residences and is most active by night as an insectivore, devouring cockroaches, spiders, mosquitoes, and other ‘creepy crawlies’. Thus, it is considered as a ‘biological pesticide’ but also eats human food such as meat, as well as cat and dog food.

In southern China, at night, it has been seen trying to enter houses by climbing along the edges of walls, emitting a chattering sound like jingling money and is thus called ‘the money shrew’!

Breeding: The musk odour, mentioned earlier, is particularly strong during the breeding season with the female shrew breeding from the age of one and then throughout the year, producing two litters each of three babies. Both parents are involved in the nest construction, which the babies occupy until they approach adulthood.

Young shrews follow their mother in a linear convoy with one baby holding on to the mother’s posterior fur with its teeth and the rest following suit, attached to the sibling immediately in front of them.

Common tree shrew

Several years ago, whilst visiting Bukit Timah Nature Reserve in Singapore, I caught a brief glimpse of this animal leaping from branch to branch of a tall tree. Initially I thought it was a squirrel, but how wrong I was!

There are nine sub-species of tree shrew in Borneo, of which the common tree shrew is but one. This shrew is found throughout the dipterocarp forests of southern Thailand, Peninsular Malaysia, Singapore, Sumatra, and Java but it has also been seen in secondary forests, plantations, orchards, and in trees near houses in those regions.

It is the largest of its species with a body length of between 16cm and 21cm, and an average weight of 190gm. Its colours vary according to its location, varying from reddish brown to black in its upper parts, with a white underside and a pale white stripe on its shoulders. The long bushy tail is a dark brown colour and its bare feet house sharp nails.

Foraging for food, they are active during the daylight hours and may be seen along the ground or amongst shrubs and holes in trees feeding on fruit, seeds, leaves, and insects. They have a particular penchant for ants and spiders.

Agile climbers of both vertical tree trunks and bushes, they can leap from branch to branch for distances of up to 60cm. Like other types of real shrew, they scent mark their territories.

Breeding: Both sexes of common tree shrew are sexually active at three months of age and the gestation period varies from 40 to 52 days. Their main reproductive time is between February and June, with the mating season starting at the onset of the rainy monsoon.

They are inactive during the dry monsoon season. It will be interesting to see what effects climate change and the uncertainty of the monsoon seasons have upon their breeding habits.

Once a litter is born, the female suckles her offspring every other day in a separate nest away from her own nest.

The young are born totally blind and survive on the richness of their mother’s milk and leave the nest after 25 to 35 days. Their lifespan in the wild is unknown, but in captivity, one lived for nearly 12 and a half years.

One species of tree shrew, the pen-tailed tree shrew (Ptilocercus lowii) is nocturnal, and is named after Sir Hugh Low (of Mount Kinabalu fame) who trapped one in Rajah Sir James Brooke’s bungalow where he often stayed in his visits to Sarawak.

Shrews of all species are particularly helpful to mankind not only as ‘biological pesticides’ as is the case of the Asian house shrew, but also because tree shrews have a close relationship to primates and have been used in research for hepatitis and breast cancer.

I have often wondered why William Shakespeare entitled one of his plays, ‘The Taming of the Shrew’. Apparently, the Shrew, Katherina is portrayed as a scolding lady screeching and squabbling shrew-like while defending her territory!