Notes on trapping shrews
Under Schedule 6 of the Wildlife and Countryside Act 1981, it’s an offence to take shrews using certain methods.
Shrews need to feed every three to four hours on insects, worms, and other invertebrates. Long periods of capture in traps can lead to high mortality rates unless certain precautions take place.
The use of unmodified traps to capture shrews requires a license to cover their intentional trapping. Use of modified traps where there is no intention to capture shrews does not need a license.
We issue licences for scientific, educational, research or conservation purposes. This includes ringing and marking.
General licence 017 - Licence to take shrews for scientific or educational purpose
If you do not need to catch shrews, drill a shrew escape hole 13 millimetres in diameter in the trap nest-box. Glue a brass washer around the hole to prevent gnawing by rodents. Glue the brass washer to the body of the trap. There is a small risk of mortality of animals that are too large to escape through the hole. Small or juvenile rodents will also be able to escape as well as shrews.
Some live capture traps allow for the sensitivity of the treadle to be adjusted. In practice this is not enough to prevent shrew capture. It is not practical to change pitfall traps. When using pitfall traps to catch shrews, you must provide food and bedding.
You should design, set and operate live traps to avoid death or injury. You should provide these traps with a nest-box containing suitable nesting material.
Ensure traps are stable. You should slope the nest chamber of the Longworth traps, to prevent water running into the bedding.
Leave plenty of suitable food in the trap. Blowfly larvae or pupae, also known as ‘casters’, are best. Use in enough sufficient numbers to provide 10 grams per trap. You must replace the food on a regular basis.
Leave dry bedding (clean hay) to provide insulation. Cover Longworth traps with surrounding vegetation or other material. This will help to insulate against extremes of temperatures.
Inspect the trap at frequent intervals. You should carry out 12 hourly inspections (dusk and early morning). This is to ensure there is ample food and bedding.
If food is not provided, shrews are likely to die if left for more than three to four hours. In such situation’s visits must be at least every four hours. Frequent trap visits will cause disturbance to the habitat and this may affect trapping success.
If shrew deaths occur, adjust the amounts of food and bedding or the frequency of inspections, as appropriate. If deaths continue, suspend trapping and seek advice.
Do not trap in very cold or very hot conditions.
Activate the door catch when traps are not in use.
Cover pitfall traps with a board (larger than the diameter of the trap). You should raise this above the ground on stones to keep the rain out.
When using pitfall traps, frequent inspection is the only safeguard against accidental shrew deaths.
Place lids on pitfall traps when traps are not in use.
The Mammal Society Booklet Live Trapping Small Mammals. A Practical Guide by J Gurnell and J R Flowerdew (2006). Available from The Mammal Society, 18 St john’s Church Road, London. E9 6EJ. Tel. 02380 010981, www.mammal.org.uk