Small Mammal Trapping at Butterfly Park

Mammal trapping had not been carried out here before so it was with great interest that the Longworth traps were collected on a bright autumn morning. Ron and Sarah had put out un-set traps baited with birdseed on two previous nights so that small mammals could get used to them. On the Saturday evening they added slices of apple or carrot, fly pupae (in case insectivorous shrews were trapped) and hay bedding to each trap and set them. Left overnight a small mammal entering one would cause the door to close behind it and it would then spend a cosy night with plenty of food and moisture from the apple.

Half of the traps were sprung and these all contained woodmice (Apodemus sylvaticus). Each individual was carefully shaken out into a bag, removed by holding it gently by the scruff of the neck, sexed, checked for parasites and then weighed. 5 females and 6 males were identified, ten were juveniles weighing 14-18g and one adult male weighing 24g. All the woodmice were carefully returned to their habitat. No shrews or voles were trapped although leaving traps out in the daytime could have produced different results.

Trapping enables the species present to be recorded and if carried out at regular intervals can show population changes. If the animals that are trapped are marked by cutting off a small section of their fur in a particular area they can be identified if they are trapped again. If this is done on several individuals and trapping is repeated this enables the total population numbers to be calculated.

It was lovely to learn about this technique, to see these small mice at close quarters and learn about the value of monitoring their populations.