The use of small mammal traps is a key method for determining the presence and abundance of small mammals. They have been succesfully used for decades by professional researchers and volunteer surveyors.
All of the traps available from NHBS are live-catch traps which should be checked regularly and food, water and bedding provided where possible.
Some small mammal species are protected by law (e.g. shrews in the UK) and you must obtain a license if you intend to trap any species of shrew. Please ensure that you are aware, and meet the requirements specified, of any relevant laws in the country you are in.