Conservation & Ecology
Small mammals
The importance of small mammals
When discussing the UK’s small mammals, it is difficult to know where to stop but, for the purposes of this article, I will concentrate on voles, mice and shrews; those above ground species that play an important role in the middle of the food chain. Compiled by Peter Britton
P
ut in its simplest terms, the food chain is: grass > invertebrates > small mammals > carnivores and raptors, with the latter decomposing on death, in the
process returning nutrients to the grass. It is this third rung on the ladder that I will concentrate on in this article. Small mammals include mice, voles, shrews, moles, bats, hedgehogs and rats, with some of these having already featured in their own right within the pages of this magazine. A quick search of the Pitchcare website will find them easily enough. So, I am going to focus on the smaller species that scurry about our wild areas and, on occasions, through domestic environs.
In a domestic environment they can cause damage to property and spread disease. For example, a house mouse will happily chew through electric cables, whilst pooing on a basis that is well beyond ‘regular’! Compared to mainland Europe, the number of species resident in the UK is considerably less, comprising those that made it to our lands ahead of the creation of the English Channel (native), plus a handful of introduced species, such as the Edible dormouse and black and brown rats. The rodents, i.e. those with prolonged front incisors, are the harvest mouse (the UK’s smallest species), wood mouse or long‐ tailed field mouse, yellow‐knecked mouse, house mouse, dormouse, bank vole, field vole and water vole. Two sub‐species of vole live on the islands of Orkney and Guernsey. The three introduced species complete the small rodent line‐up.
Although its external appearance is generally that of a long‐nosed mouse, shrews are not rodents. They are, in fact, more closely related to moles and hedgehogs, being related to rodents only in that both belong to the Boreoeutheria Magnorder which comprises all placental mammals, including humans.
Shrews have sharp, spike‐like teeth, not the familiar gnawing front incisor teeth of rodents.
MICE
Leaving aside the house mouse which, as its name implies, lives almost exclusively in buildings feeding on scraps, insects and spiders, the dietary requirements of mice is varied.
Mice are primarily seed eaters, particularly those of oak, beech, ash, lime, hawthorn and sycamore. They also eat small invertebrates such as snails and insects, particularly in late spring and early summer when seeds are less plentiful. They also consume berries, fruits, and roots and, if seeds or stones are plentiful on the ground, they carry them back to their nests/burrows for storage. The gestation period of mice is around twenty to twenty‐six days, and they give birth to a litter of up to fourteen young (average six to eight). One female can have up to ten litters per year, with the young often becoming pregnant once weaned. Females can remate whilst still feeding the previous litter, so it is clear that the mouse population can increase very quickly. Breeding occurs throughout the year for the wood mouse and between February and October in the Yellow‐knecked mouse. These mice do not hibernate, but can go into a state of torpor should the winter prove excessively harsh.
The dormouse is a different animal altogether. Not only is it strictly nocturnal, it
114 I PC DECEMBER/JANUARY 2018
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