Finding out about small mammals

Emma Chaplin
, 03 May 2022
Finding out about small mammals
Yellow-necked mouse © Arthur Hoare

By Emma Chaplin

Communications Officer

Ecologist and natural history trainer Laurie Jackson has been running a number of courses for Sussex Wildlife Trust for many years. I went along to her 'Introduction to Small Mammals' course at Woods Mill in April. 

The day-long course covers how to identify small mammals, as well as their habitats, conservation status, surveying and monitoring. The course works for attendees, like me, simply wanting to improve our knowledge and identification skills, as well as those with a more academic or career-oriented interest. 

A number of Longworth traps had been set during the night around Woods Mill nature reserve. They are specially designed to safely trap small mammals for this type of survey. One of the first things we did was to head out to check them.

Trapping is a way of surveying the range and health of small mammals in a given place, and it is, of course, done with great care for the animals. Laurie explained that the traps need to be checked within a few hours of being set, and you need to think about weather conditions, putting them under some vegetation and never in hot sun. 

Traps had been set at regular intervals in areas around the reserve where the small mammals are expected to be found, with a ribbon marker indicating where each one was. In the previous few days, they had been left in place, open with food inside, so the mammals got used to them. Then, during the night before the course (which starts at 9am), they were set so that the door would shut once a mammal was inside. 

Each trap has a bedding chamber, with lots of bedding inside (sawdust and straw), as well as fresh food that includes a water source, chopped apple and carrot, as well as hamster food. Mice and voles are happy feeding on a range of plant material, but shrews are insectivores , so some dry mealworms are also included (live ones would remove themselves!).

If the door was shut when we checked it, it meant there was probably a mammal inside. A 'calling card' (poo) on top was another sign. Laurie showed us how to open the trap carefully, and check on the mammal inside very carefully. One lesson for humans was to always roll your sleeves up (as you don't really want a mouse running up inside). 

We found a number of Bank Voles, one of which we weighed to learn how to do it, and one Yellow-necked Mouse. You always know how many traps you've set, and you 'count them in and count them out' so you don't forget any.

Bank Vole
Dennis Hunt

We then reset all the traps to check them again a few hours later, and headed back to the Mill to learn more about identification (considering, for example the colour of the fur, both on top and underneath, ear size and position, shape and size of snout and tail etc. Some have prehensile tails, some don't).

In terms of behaviour, we'd already learnt in Woods Mill garden that mice are excellent climbers and Yellow-necked Mice are especially feisty! Laurie told us that, although Dormice do still have their moments of being sleepy (when they are in torpor), when they are awake, they are actually super speedy.

We discussed habitats, nests etc and learnt that Harvest Mice and Hazel Dormice weave lovely nests (Harvest Mouse nest below).

Harvest Mouse nest
Laurie Jackson

Laurie talked about looking out for signs of mammals, such as latrines and runs in the grass. For many species a latrine is more than just a pile of droppings, and for species like Water Voles they can be territorial markers. We learnt about field signs of mammals - for example, Dormice have a distinct method of nibbling food, as does the Bank Vole.

She explained that there is still lots we don't know about the social structures of small mammals.

We learnt about conservation status and legislation in relation to mammals. The main threats to small mammals are thought to be habitat loss, pesticides and roads, as well as the added pressure of new predators such as cats and American Mink.

All in all, it was a fascinating day, with a lot of ground clearly explained and/or demonstrated. I'd heartily recommend one of Laurie's courses. It was fascinating, with a good mix of practical and theoretical. We all learnt a lot, and were given a print out of the presentation slides as well.

Laurie is teaching a course of the Ecology of the Hazel Dormouse on 7 September 

For information about adult education and other events we run  - see here 

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