Small mammals in your garden.

Hello everyone! This week’s garden wildlife blog will focus on some of the smaller, more elusive species that exist in our gardens. Gardens support a range of native UK mammal species, providing a stable habitat and food supplies. Almost all gardens, even small ones and those that reside in the centre of the city will occasionally be visited by a small mammal. Small mammals are ‘small-bodied’ creatures, especially when compared to other mammals, with most weighing under 1kg. Some are truly tiny, such as the Etruscan shrew which weighs on average 1.8 grams. The smallest of mammals that occasionally visit or choose to set up living quarters in our gardens includes the wood mouse (Apodemus sylvaticus), bank vole (Myodes glareolus), short-tailed field vole (Microtus agrestis), common shew (Sorex araneus) and pygmy shrew (Sorex minutus).

The closer you live to parks, green areas, nature reserves and the country side, the more chance you have of seeing small mammals and are more likely to have a variety of species. Most British mammals are nocturnal or crepuscular (active at dusk and dawn) and are therefore active during the hours when we like to snooze. Those that are busy during the day will likely hide in the undergrowth of hedges and scrubs, and your presence, if you are not careful, will flush them. They don’t become docile around humans the same as some birds do, they will however take to feeding stations, if they can access them without the risk of predation. Many of these species are nocturnal naturally, and not as a direct consequence of humans being active in the day, although it might contribute to those in gardens. To survive, it makes sense to be more active while those around you are not, especially if they want to eat you, although this isn’t always the reason why some animals take on the nocturnal lifestyle. Sometimes competition for food can drive animals to seek alternative options, such as nocturnal insects, like some nocturnal birds do. However, for most there are predators at large in the day that small mammals fear, such as birds of prey, carnivorous birds and other larger mammals. Even weasels and stoats, whom you might think could be an exception when you see their optimistic prey choices, often being a mammal much larger than themselves, they can also be picked up by birds of prey and larger mammals.

The smallest of mammals you are likely to see in your garden fall into three categories: shrews, voles and mice. They occasionally all get lumped into one group, that being rodents. However, shrews along with hedgehogs and moles are classified as insectivores, while mice and voles are rodents. Shrews are easily distinguishable with their pointed snout, which is helpful if you only get a glimpse of it scurrying past. The common shrew (Sorex araneus) lives a short busy life, feeding every 2-3 hours and living for only 1-2 years. They weigh between 5 – 15g, have tiny eyes, very small ears and are brown on top and grey or silver below. Then there is the pygmy shrew (Sorex minutus) (image below), weighing in at only 2 – 6g. Like the common shrew, it has tiny eyes, small ears and a pointed snout. If you haven’t seen either of these species before, you might find it difficult to tell them apart, but there is a way to tell; pygmy shrews are much smaller, and their tails are two-thirds the length of their bodies (common shrew tails are half the length of their bodies). Both species spend their whole lives hungry the entire time, as they need to eat 80 - 90% (common) and up to 125% (pygmy) of their own body weight. So, they spend most of their time hunting and eating, like a lot of us currently are in lockdown, hunting for products on the shelves and eating way too much. Both species like dense vegetation, and their nests are made of woven grass.

Pygmy shrew 

The wood mouse (Apodemus sylvaticus), or long-tailed field mouse as it is otherwise known, are also common visitors to gardens (image below). They are our most common species of mouse. Noticeably larger than shrews, they can weigh up to 25g and have a distinctively long tail (wood mice tails are between 7 – 9.5 cm in length), as the name suggests. They have an orange-brown body, with large eyes and very large ears. They too have a pointed snout, which along with a hairless tail and large ears and eyes, is what classifies them as ‘true mice’. Fury-tailed mice like the tiny hazel dormouse are not classed as true mice. Wood mice are hard to see, they are mostly nocturnal and prefer to stick to dense cover. If you are lucky enough to spot one in the day, be as quiet and as still as possible, and you just might get a good look. They don’t live very long; few adults survive from one summer to the next. However, how they remain common is by breeding successive litters of 4 - 7 young between March to October. They may even breed over the winter if there is a good food supply.

Wood mouse

Next, we have voles - mouse-sized, blunt-nosed, short-tailed rodents. The two species you are likely to see in your garden is the field vole and bank vole. Both species naturally live in grassland, farmland, woodland, heathland and moorland, but have taken refuge in our towns and gardens also. The field vole is grey-brown on top, and grey underneath. Both species have small ears and eyes and short tails. The bank vole is a chestnut brown on top and white underneath (image below), allowing you distinguish the two. Another way of telling the two apart is by checking the length of their tail; the bank vole has a short tail, under half the length of its body, while the tail of the field vole is around a third of its body length. They have dissimilar diets, with the bank vole preferring fruits, nuts and small insects, and the field vole eating seeds, roots and leaves. Field voles are more prolific breeders, having up to 3 – 6 litters a year with up to seven young. Bank voles have between 3 – 4 litters, with 3 – 5 young.

There are a couple of techniques you can use to see these mini cryptic creatures; their shy nature requires us to use more elaborate methods. One of the first things you can do is build a ‘small mammal footprint tunnel’. Commonly used to observe hedgehogs, these tunnels are great for smaller mammals too. They are a simple plastic tunnel with food to tempt animals in and with inkpads and paper, it means when the mammals enter the tunnel to take the food, they leave inky footprints. You can then use the footprints to identify the species. Click on the link below to learn more.

Another method you can use is camera trapping. Create a safe space for small mammals to feed, such as in a box or at a feeding stations that is adjacent to grass or scrub, so that they feel like there is somewhere safe to run to if needed. For example, see the post on our Facebook page advertising this blog, it contains footage of small mammals caught on camera using small mammal camera trap box. This is simply a wooden box, with a feeding area and a camera attached at one end. I created this to observe the small mammals in the office garden, see if you can guess what species they are!

I used the link below for inspiration, but if you don’t want to build one you can simply buy one. Camera traps are easy to use, and you can order them from amazon while in lockdown. If you want to learn more about camera traps and which ones to buy, feel free to email me at Paige.Donnelly@RSPB.ORG.UK.

Now I hope you have fun small mammal hunting!