Environment A to Z of Canal Wildlife
A to Z of Canal Wildlife: V - Z

Vole *

The water vole, sometimes incorrectly called the water rat, was once common along the banks of canals, rivers, ditches and lakes. Its correct name is the Northern Water vole Arvicola terrestris, and as it is about the same size as the brown rat is often confused with it. Both are good swimmers and are usually spotted when they are surprised and dive into the water to make a quick getaway, but the Water vole maVolekes a distinctive ‘plop’ and invariably paddles away under the water using all four legs, whereas the rat swims on the surface. Unlike rats, Water voles require clean, unpolluted water where they feed on aquatic plants and vegetation close to the water’s edge. Water voles have long dark brown glossy fur, a rounded face with a blunt nose, small eyes and furry ears, and a short tail. Ratty in Kenneth Grahame’s enchanting book ‘Wind in the Willows’ was a Water vole.

The endearing Water vole was once a familiar sight on waterways throughout the country but sadly is now in catastrophic decline with only about a tenth of the original numbers remaining and their survival must be in doubt. The reasons for this decline are not fully understood, but the loss of bankside habitat, pollution, and altered riparian management could be to blame. However the arch culprit is thought by many to be the mink. The escape, or release, of farmed mink, an extremely effective predator of the Water vole, and its spread into the natural environment is believed by many to have devastated the vole population.

Although Water voles are rarely seen, the clues to their existence are more easily spotted than the animals themselves, but once they are found, watching them is easy; just sit quietly, still and below the skyline on the bank opposite their burrows and runs and wait with binoculars ready. Although they do not hibernate, they are not active in the winter so between March and October is the best time. Their territories can be quite long, sometimes well over 100 metres of bankside, and are based around a burrow system. Runways, up to 10 cm (4 in.) wide and within a metre of the water can easily be seen through the bankside vegetation. Also bare flattened areas form where they regularly enter and leave the water. The burrows can be extensive with entrance holes about 8 cm (3 inches) across, slightly wider than high, above and below the water line.

Water vole holes have been blamed on many occasions for leaks in canal embankments, sometimes leading to catastrophic collapses, flooding and de-watering lengths of canal. So much so, that it used to be part of a lengthsman’s duties to control the voles on his section! (Now highly illegal, see note below). Immediately around the holes the vegetation is closely grazed to form a ‘voles lawn’. They also have feeding stations at favoured places, close to the waters edge. They fetch pieces of cut vegetation which they heap up on bare patches of soil, prominent stones or tussocks of vegetation which they then eat at their leisure, leaving neat piles of leftovers. Favoured feeding sites often have a latrine close by where large numbers of droppings are deposited. A flattened mass of old droppings is topped up with fresh ones. The faeces are cylindrical and blunt-ended 8 to 12 mm long and 4 to 5 mm wide and are also used to mark the boundaries of their territories.

Water voles usually produce between 2 and 4 litters of 4 to 6 young each year. They have many enemies such as weasels, cats, foxes, owls, other birds of prey and pike and, as explained above, their numbers are declining. Hopefully the continuing restoration of our derelict and dried-up canals will provide suitable environments for them and arrest the decline of this enchanting creature

Warning - Important note. The Water vole has legal protection under the Wildlife and Countryside Act 1981 (as amended). It is an offence to intentionally damage or destroy or obstruct access to any structure or place which they use for shelter or protection, or to disturb them. Severe fines and forfeiture of vehicles and equipment can be imposed. Further information can be obtained from English Nature, Environment Agency, British Waterways or W&BCAT Environment Advisor.


Widespread throughout Britain, weasels are our smallest and probably most numerous carnivores. They are found in a wide range of habitats which include urban areas, lowland pasture and woodland, marshes and moors. Weasels are less common where their small mammal prey are scarce, such as at higher altitudes and in dense woodland with sparse ground cover.

Weasels specialise in hunting small rodents and their numbers depend on the abundance of their prey. The weasel's small size enables it to search through tunnels and runways of mice and voles. Access to tunnels means weasels can hunt at any time of the day or year. They do not hibernate and can hunt even under deep snow. Additional prey such as birds, eggs and young rabbits may be taken, particularly if rodents are scarce.

Dens are usually nests of former prey taken over by weasels, and may contain the remains of food from several days meals. In cold climates the nests are often lined with fur from prey. A weasel's home range usually contains several dens and resting places that are visited at intervals.

Only one in 80-90 weasels survives to over 2 years old. They are small enough to be regarded as or confused with prey by almost all other predators; hawks, owls, foxes, cats and mink have been known to eat them.


WillowThe willows of Britain have many different names including osier, withy, sallies, palm, sallow or in Scotland, saugh and come in many sizes from ground hugging shrubs to tall, stately trees. They are fast growing but not long lived trees, 50 years being old. Each tree is either male or female, and can be reproduced from cuttings which will be the same sex. They all produce flowers in oval fluffy catkins, hence pussy-willow.

Male and female catkins are similar and emerge in March before the leaves; both produce nectar, which attracts insects for pollination, although some pollen is carried by the wind. Female catkins hold many seedpods, which quickly ripen, to split and release many tiny winged seeds which are short lived and will only sprout on damp soil. So willows are generally only found near water and, thus, are common along our waterways.

Particularly common along the canal is our tallest willow, the Crack Willow Salix fragilis which can reach 90 feet high. It gets the name because its small yellow barked twigs easily break away at the joints with a sharp crack. It has long, slender, silver green leaves and will grow rapidly. Often it grows branches that are too large for the trunk to support and they split away. Where these stranded branches touch the ground or fall into the water they will easily take root, as will fallen twigs and smaller branches. The wood is pale yellow and not very durable but when young is tough, pliant and light. Thus Crack willows are often pollarded to reduce the chances of splitting and to quickly provide more timber. Logged branches soon dry to provide good firewood, which burns well but is liable to spit. Thin young poles can be used to make woven products.

Walking the towpath you may have noticed long lines of evenly spaced willows growing alongside the canal, or on derelict drying canals along the bed, and wondered how Mother Nature could be so precise! The answer lies with the pollarded Crack willows natural ability to provide ‘free, standard sized fence posts’. After just a few years a pollarded tree will grow numerous reasonably equally sized straight branches, a virtue exploited by the farmer wishing to fence his stock. These soft poles were easy to cut from the tree, cut to length and drive into the soft damp canal to carry the barbed wire. But these free posts soon sprouted roots and the evenly spaced fence posts soon became an evenly spaced row of trees!

Water Boatman


Where the water near the canal’s edge is reasonably clean and clear of weeds it should be easy to spot the common water boatman.

There are four very similar species of which the most common is notonecta glauca. This aggressive bug swims, with jerky movements, upside down just beneath the surface waiting to attack it’s prey, which it catches with it’s piercing mouthparts injecting a poisonous saliva. Few small creatures escape it and, although only about 15mm (? inch) long, it will even catch small fish and tadpoles.

The slightest movement in the water is detected by the brown and yellow predator whose body resembles a tiny boat. The wings form the hull and the oars are the long third pair of legs. It’s habit of swimming upside down gives it it’s other name of backswimmer. When it dives it carries a store of air with it trapped by a coat of bristles on it’s body, this bubble of air gives it a silvery appearance. The female lays individual eggs on the stems of water plants, which hatch out after two months into larvae that resemble the adults but are wingless. However they soon grow wings with which to fly from water to water inhabiting any still water, including canals, ditches, ponds, cattle troughs, even puddles and the occasional water butt. So beware, these aggressive little creatures have been known to bite!