Mice and voles

Mice and voles are small rodents that sometimes cause problems in gardens and greenhouses.

Strawberry fruits picked by field mice

Quick facts

Common name Mice and voles
Scientific names Apodemus, Myodes and Microtus species
Plants affected Many, including pea seedlings, apple and strawberry fruits, crocus corms
Main causes Mice and voles eat the foliage, seeds and fruits of many plants, and also gnaw bark from woody plants
Timing All year round

What are mice and voles?

Four species of mice and voles sometimes cause damage in gardens. The wood mouse, Apodemus sylvestris, the short-tailed vole, Microtus agrestis, and the bank vole, Myodes glareolus, are widely distributed in the UK. The yellow-necked field mouse, Apodemus flavicollis, mainly occurs in southern England and Wales. These mainly nocturnal small rodents are active all year round. Most of the time the population levels are relatively low and little damage is seen but mice and voles can reproduce rapidly under good conditions, leading to population explosions and damage to plants. 

Symptoms

Mice differ from voles in having tails that are longer than their bodies. The head of a vole, when viewed from the side, has a rounded appearance, whereas a mouse's head is extended forwards. Both mice and voles can feed on a wide range of plants.

Paired grooves may be seen on stems, crocus corms and stored apples, where the rodents' incisor teeth have gnawed at the food item. Holes may be seen in the soil where mice or voles have dug down to feed on bulbs, corms or germinating seeds. Remnants of seedlings may be scattered on the soil surface. Field mice sometimes bite off strawberry and other fruits before they are ripe and leave the berries in small heaps among the plants. Soft areas in a lawn with small heaps of soil on the surface are likely to be due to voles (as opposed to moles) tunnelling just beneath the surface.

Mice and voles can eat the recently sown seeds of peas, beans and sweet corn and kill seedling plants by grazing on the foliage. In cold weather field mice often enter greenhouses and cold frames, where they can destroy many seedlings overnight. They can also enter sheds and feed on stored fruits, such as apples.

Voles sometimes eat the bark of a wide range of woody plants, particularly in winter when vegetation is frozen and less palatable. If bark is lost from all or most of the circumference of a stem, then growth beyond that point dies. On evergreen plants, such as yew and ivy, the dieback may not be noticeable until later in the spring or summer.

Voles make a network of shallow tunnels in the soil and this can give lawns an uneven and soft surface.

Crocus corms and tulip bulbs are often eaten, especially in the first autumn-winter after planting. Established bulbs and corms are less susceptible.

Control

Non-chemical control

Trapping can be effective for mice in a garden situation, although voles can be harder to control. Break-back traps of the type used against house mice can be effective when set in places where damage is occurring. Pieces of carrot or dessert apple are effective baits for voles, and peanut butter for mice. When using traps or baits out of doors, they should be placed under covers to reduce the risk of other animals interfering with them. Birds are particularly vulnerable to accidental trapping.

Non-lethal traps are available but these must be checked at least twice a day, to comply with animal welfare legislation, and the rodent released some distance (several miles is usually recommended) from the trapping site.

At times when mice or vole populations are high, it can be difficult to make much impression on their numbers. Fortunately these rodents do not sustain high populations for long and their numbers will drop back to normal low levels.

Fitting young or newly planted trees with tree spirals (biodegradable spirals based on potato starch are available) can help reduce damage to bark.

Chemical control

Poison baits can be used against field mice and voles but may not be very effective during spring-autumn when there are plenty of alternative food items available. Only baits approved for outdoor use can be used in gardens, and every care (by following the manufacturer's instructions closely) must be taken to avoid non-target species consuming the bait. Baits approved for indoor use can be used in sheds and greenhouses, but again great care should be taken. Accidental poisoning of non-target animals is illegal.

Dead animals should be disposed of by burying them or placing the corpses in a polythene bag in the dustbin. Always wear rubber gloves when handling traps, bait or dead rodents.

Biology

Mice and voles remain active all year round. The breeding season is between spring and autumn, when field mice and voles can produce up to five litters of four to six young. The young are born underground in nests made of dry grass. These rodents are heavily predated by cats, foxes, stoats, weasels, owls and other birds of prey. 

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