Guidance - Shrew trapping methods

This document sets out which guidelines are to be followed in trapping of shrews to ensure that their mortality is minimised.

No formal training is required to set live capture small mammal traps, although if not adapted with a 12mm hole, their use must be licensed to cover intentional trapping of shrews. Setting them to ensure that shrew mortality is minimised requires certain guidelines to be followed. 

Some live capture traps allow for the sensitivity of the treadle to be adjusted. In practice this is not sufficient to prevent shrew capture.

These methods have been outlined to help prevent the unnecessary death of shrews by freezing, starvation and dehydration and contribute to reducing stress related mortality.

Time between checking 

Shrews are insectivores that need to feed every 3-4 hours. Traps therefore must be checked at least every 4 hours. At each inspection the following should be checked:

• Food Leave food in the nest box. Use blow fly pupae (Calliphora spp.), called “casters” by the fishing fraternity, in sufficient numbers to provide 10g per trap. These can be frozen and used as required.
• Bedding Leave bedding in the nest to provide insulation. Use clean, dry hay, non-absorbent cotton wool or shredded paper (to be changed if damp).
• Cover Traps should be covered with surrounding vegetation or other, to insulate against extremes of temperature.
• Position Traps must be stable and the nest chamber of the Longworth must be sloped to prevent water running into the bedding.
• Adapting traps with 12mm hole A brass washer should be glued around the hole to prevent gnawing by rodents which can soon enlarge the hole. The brass washer should be glued using epoxy resin to the aluminium or plastic of live capture small mammal traps.

For more information: J Gurnell and JR Flowerdew. “Live Trapping Small Mammals – A Practical Guide”. Available from the Mammal Society 

Churchfield, S. 1990. “The Natural History of Shrews” Christopher Help pp161-166 

Little, J & J Gurness. “Shrew Captures and Rodent Field Studies” J. Zool., London (1989) 218, 329-331

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