Oct 18, 20215 min read

Small mammals of British gardens

There are four species of mice found in the UK. The wood mouse, also known as the field mouse (Apodemus sylvaticus) is distinctive by its large ears and long tail. They feed on seeds, fruit and nuts as well as invertebrates. The yellow-necked mouse (Apodemus flavicollis) has a yellow band around its chest, is slightly larger and less common. House mice (Mus musculus) are commonly sighted due to their association with buildings. Finally, harvest mice (Micromys minutus) are distinctive as the smallest rodent in the UK with golden fur that is found in reed beds, marshes and verges.

There are three species of vole: bank (Myodes glareolus), field (Microtus agrestis) and water (Arvicola amphibious). The most likely ones you will see are bank and field voles. Compared to mice, voles have much shorter tails, more rounded snouts and smaller eyes and ears in relation to their size. They two common species look very similar, but field voles have tails that are 30% the size of their body and are a more grey-brown colour whereas bank voles are more red brown, and their tails are 50% of their body length. Bank voles tend to eat a wide range of roots, fungi, vegetation, fruits and nuts and sometimes small insects. Field voles eat stems and leaves of grasses and even moss. There are also water voles that are a lot bigger and darker and are found near canals.

There are four species of shrew native to the UK, with the greater white-toothed shrew (Crocidura russula) only found on islands. Shrews have a distinctive look in relation to all the other small mammal species, with their long-pointed nose, rounded head and very small eyes and ears. There is the common shrew (Sorex araneus) which you will most likely find in your garden with three different colour tones and the rarer and smaller pygmy shrew (Sorex minutus) with only two-colour tones. There are also water shrews (Neomys fodiens), but they are more common in wetland and water habitats.

Small mammals are massively important for their role in localised ecosystem functioning but are sadly rarely viewed as useful and only as pests. They are a main food source for a large number of other species such as birds of prey like barn owls, kestrels and buzzards, weasels and foxes. Without the small mammal populations, the other species would struggle to survive. A study has been done on field vole populations and estimated just under 1 million were predated each year. They also have a major impact on plant communities and because of their high reproductive rates, any data collected on their abundance and presence can help show how the wider ecosystem is being impacted by changes in the environment.

Slug pellets are a common tool used in gardens these days, but the chemical used in many called metaldehyde can be disastrous for all wildlife. Small mammals eat the pellets and then larger animals eat them, so the chemical harms them too and impacts the wider ecological area. This can also affect pets that may eat birds or small mammals. Some alternative ideas that may reduce a slug problem are creating habitats and feeding areas for birds as well as ground beetles which are their primary predator. Improving water logging will reduce the habitat that slugs prefer and even encouraging hedgehogs may help. As a last resort, there are more wildlife friendly slug pellets that contain ferric phosphate. We have some on our website called ‘Slug Rid’.

It might be seen as the easiest solution to just kill any problematic small mammals you find in and around your home when in fact it doesn’t have to be this way! It is a very simple process to catch the individual in a similar trap that we use to collect data on them and then release them a distance away will be more than effective. Not only will this mean you aren’t hurting the localised population, but you also get to see them up close and can appreciate how sweet they are! We sell these small mammal traps on our website that can be reused as many times as needed.

Domesticated cats cause serious ecological harm all over the world thanks to their uncontrollable diet of small mammals and birds! This is majorly impacting their populations and has even caused extinctions of species, especially on islands. One of the most famous examples is the on an island near New Zealand where the lighthouse man’s cat Tibbles managed to make the Stephens Island Wren go extinct only a year after its discovery! It’s a tricky situation and one that is not easily solved! Some people now keep their cats as indoors only which is only a viable option if there are plenty of enrichment for them to replace their outdoor freedom. A less stringent action could be to limit the time of day your cat is allowed outside to avoid hunting at dawn and dusk or create a safe area outdoors they can explore. A study has also shown that increasing playing with your cat has a significant reduction is killing wildlife as well as making sure their diet is providing them with all the required nutrients and animal protein. Finally, a collar with a bell or bright colours can help reduce predation of small mammals and songbirds to a certain extent, although a quick release catch on the collar is necessary so that they won’t get caught!

At university, I was involved in small mammal trapping on campus to collect data for ERCCIS (Environmental Records Centre for Cornwall and the Isles of Scilly). It was also a great opportunity to allow other students to get involved and learn how and why we do it. The basic principles are putting out small ‘traps’ filled with bedding and food that shut when something enters that is then released the following morning. First, we record a number of measurements on identification of species, body length, tail length, weight and sex and if we were doing several days of trapping, we would make a small mark by trimming some fur, so we knew we had already trapped that individual. This process is completely safe for the small mammals, with some individuals even getting to like it so much that they keep getting caught which can cause biases in the data! It is also only carried out in fair weather so that they are not at risk from heavy rain or extreme cold.