Pygmy shrew  (Sorex minutus)

Protected under Schedule 6 of the Wildlife and Countryside Act, 1981 (3).

As both the common and scientific names suggest (minutus means small), the pygmy shrew is tiny (4), in fact it is the smallest native British shrew (2). It has a pointed snout and greyish-brown fur that becomes paler on the underside (4). Compared to other species of British shrews, the pygmy shrew has a relatively longer, hairier tail (2). Like other shrews of the genusSorex, this species has red-tipped teeth, formed by the deposition of iron, which toughens them against wear-and-tear (2).

This is a widespread and fairly abundant species throughout the British mainland; it also occurs on many offshore islands except Shetland, the Channel Isles and the Isles of Scilly (5). On continental Europe they are also widespread, although they are absent from some southern areas (5). It is the only shrew that occurs in Ireland (2).

Occurs in a very broad range of terrestrial habitats, wherever there is adequate ground cover (4).

Pygmy shrews are active by day and night, interspersing bouts of activity with rest periods (5). They are typically solitary, and will defend their range against other pygmy shrews (4). They make surface tunnels through vegetation (4), and feed on invertebrates such as beetles, spiders and woodlice that can be found in the leaf-litter (5), but they very rarely tackle earthworms, possibly because they are too large for them to handle (2). Shrews are well known for their voracious appetites; due to their small size and high metabolic rate, they have to eat regularly, and consume about 125% of their own body weight in food each day in order to stay alive (2). They do not hibernate, as they are too small to store the fat reserves needed to sustain them, instead they have to remain active during winter (2). Births occur between April and August, peaking in June (5). Two litters are usually produced each year, each consisting of between 4 and 7 young (5). The young overwinter as immatures (4), reaching sexual maturity the following year, although some females born early in the year may even breed in the year of birth (5). Main predators of pygmy shrews are owls, raptors, mustelids, foxes and cats. The maximum life span is 16 months (5).

Shrews belonging to the genus Sorex are known to produce ultrasound, which may be used in a primitive form of echolocation(6).

The small size of the pygmy shrew makes it particularly susceptible to environmental unpredictability, such as adverse weather (5). Habitats loss, heavy grazing and the use of pesticides are also potential problems (5).

All shrews are protected under the Wildlife and Countryside Act, 1981 (3). This diminutive shrew will be likely to benefit from agri-environment schemes that encourage farmers to reduce the density of grazing livestock on their land, and to create conservation-friendly field boundaries (5).

For more on this species see: Shrews of the British Isles (1988), by Sara Churchfield. (Shire Publishing Ltd).

• Agri-environment schemes: these schemes allow the government to compensate farmers for using methods that benefit the environment. The two main initiatives in the UK are the Countryside Stewardship Scheme and Environmentally Sensitive Areas. Since October 2000 these have formed part of the England Rural Development Programme (EDRP), administered by DEFRA, the Department of Environment Food and Rural Affairs. For more on these initiatives see: http://www.defra.gov.uk/erdp/erdphome.htm
• Echolocation: detecting objects by reflected sound. Used for orientation and detecting and locating prey by bats and cetacea (whales and dolphins).
• Genus: a category used in taxonomy, which is below 'family' and above 'species'. A genus tends to contain species that have characteristics in common. The genus forms the first part of a 'binomial' Latin species name; the second part is the specific name.
• Mustelids: a family of carnivores that are characteristic of the northern temperate latitudes. Relatively primitive with short, stocky legs. They have long sharp canine teeth.
• Ultrasound: sounds that are above the range of human hearing.

1. National Biodiversity Network Species Dictionary (May 2002) http://www.nhm.ac.uk/nbn/
2. Churchfield, S. (1988) Shrews of the British Isles. Shire Natural History. Shire Publications, Aylesbury.
3. Morris, P. (1993) A red data book for British mammals. Mammal Society, Bristol.
4. The Mammal Society: pygmy shrew fact sheet (August 2002): http://www.abdn.ac.uk/mammal/pygmy_shrew.shtml
5. Macdonald, D. W. & Tattersall, F. T. (2001) Britain's mammals- the challenge for conservation. The Wildlife Conservation research Unit, Oxford University. www.wildcru.org
6. Macdonald, D. W. (2001) The New Encyclopedia of Mammals. Oxford University Press, Oxford.