The descriptive text, below the map, is from the Cornish Red Data Book (2009). The map on this web page depicts the organisms distribution and shows the records made pre-2000 and those made since.
Range & Status
Widely distributed through Europe and Asia (Harris & Yalden, 2008), though absent from the Iberian Peninsula and Ireland (Corbet & Harris, 1996). In Britain it is native and locally common, being widespread on the mainland. It is also present on a number of Scottish Islands, Anglesey and the Isle of Wight, and is only locally distributed in parts of northern Scotland (Harris et al ., 1995). Water Shrew has been recorded at 420 metres above sea level in Wales (Harris & Yalden, 2008). A total pre-breeding population estimate (of low reliability) of 1,900,000 is given for Britain by Harris et al . (1995). A slightly larger estimate
of 2,000,000 is given by Macdonald and Tattersall (2001).
Widespread throughout Cornwall, but poorly recorded (Howie, Jelbert & Doyle, 2007), the presence of Water Shrew is difficult to survey, as they are small, elusive and nomadic. The Cornwall Water Shrew Survey (Howie & Stokes, 2003) identified the most popular and effective way of collecting records of this species was through a public appeal for sightings. From the results of this survey 53% were records of cat-kill corpses, 23% were of live sightings and 13% from Barn Owl Tyto alba pellets. Only 11% of records were due to active surveying, using specially designed survey tubes. The success of cat owners in gathering records was no doubt aided by the fact that cats catch, but appear not to eat Water Shrew.
Habitat & Ecology
Found mainly beside unpolluted, fast flowing rivers and streams; also found in gardens, by ponds, drainage ditches, canals and especially numerous at watercress beds (Harris & Yalden, 2008). On occasion they are found far from water in deciduous woodland, hedgerows and grassland, and in Cornwall they have been found some distance from water; near hedges, from trapping with Longworth traps. In Scotland they occur on rocky shores among boulders (Corbet & Harris, 1996; Harris & Yalden, 2008). Food includes a variety of invertebrates, amphibians and fish. Their dominant prey species at all times of year are freshwater crustaceans and cased caddis-fly larvae (Corbet & Harris, 1996; Harris & Yalden, 2008).
Habitat destruction is thought to be the major problem, particularly in southern England, especially from bank-side modification and the resulting vegetation changes, along with water quality. There is some evidence that overall water quality in Britain is declining (Harris et al ., 1995). Predation from domestic cats may be a threat in habitats close to human habitation. In Cornwall, fresh, dead animals, resulting from The Cornwall Water Shrew Survey (Howie & Stokes, 2003) were subject to necropsy examination by WVIC. These investigations revealed no significant diseases or parasites. It was noted, however, that this species has exceptionally large mesenteric lymph nodes compared to other
animals of a similar size.
There are considerable problems in monitoring population changes with this species (Harris et al ., 1995). However, some research has been carried out by CWT through four small scale surveys (Perkin, 2000; Goddard, 2000; Varnam & Craze, 2001; Howie & Stokes, 2003). The Water Shrew is listed on Schedule 6 of the Wildlife and Countryside Act; protected from being trapped without a licence. Listed (long list) as a globally threatened/declining species (BSGR, 1995), it is not included in the Biodiversity Action Plan list for Cornwall.
I.J. Bennallick, S. Board, C.N. French, P.A. Gainey, C. Neil, R. Parslow, A. Spalding and P.E. Tompsett. eds. 2009. Red Data Book for Cornwall and the Isles of Scilly. 2nd Edition.Croceago Press.
The Cornish Red Data Book Project was led by the Cornwall and Isles of Scilly Federation for Biological Recorders (CISFBR). The full text and species accounts (minus the maps) are available on the CISFBR website.