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A brief natural history of the water vole
The water vole (Arvicola terrestris) is a rodent; it is considerably larger than our other British vole species - bank vole (Clethrionomys glareolus), field vole (Microtus agrestis)and Orkney vole (Microtus arvalis).
As their name suggests water voles live by waterways throughout mainland Britain preferring slow flowing rivers and streams. The water vole uses it’s large incisors to burrow into the banks of streams or ditches to create a system of tunnels and chambers. They use the water as a natural defence system ‘“plopping” from the bank into the water when danger threatens before kicking up a mud screen in the water to blind any following predator.
Underwater burrow entrance
The entrance to their burrow is generally on or just below the water level helping to protect them from some of their natural predators - weasels (Mustelia nivalis), stoats (Mustelia erminea), foxes (Vulpes vulpes) and grey herons (Ardea cinerea).
Water voles are mainly vegetarian – they have been recorded feeding on around 227 different plant species -although they may consume insects, molluscs and occasionally dead fish. Water voles are sometimes mistaken for brown rats (Rattus norvegicus) which commonly also live in river banks and are excellent swimmers. They can be distinguished by their shorter, more rounded bodies, blunt muzzles, bright orange incisor teeth, small ears and short, lightly-haired tails.
Young water voles bred in captivity
Water voles are typically a rich brown in colour with black guard hairs and a greyish-ochre belly. Coat colour does vary between populations and in northwest Scotland some populations are predominantly black. Other coat colours include albino, cinnamon, bright buff and pied, although rare, have been recorded, while small white markings – e.g. on tail tip, forehead, chest, back or paws – are common.
Adult female water voles occupy territories of around 70 metres of banking during the breeding season of March-September, during which time they can produce up to four litters of between 3 to 9 young. These are born naked and blind in an underground nest of dried vegetation gathered by their mother. Antagonistic behaviour between females at this time may involve teeth chattering, flank scratching and tail biting.
Young vole bred in captivity, approximately 2 weeks of age
Male animals patrol a territory - usually about 170 metres of banking - containing multiple female territories. When the young are fully weaned at approximately 4 weeks, they disperse to find their own territories a factor which can be a problem in isolated water bodies. Water voles mark their territories with faecal latrines, which are clearly visible in the summer months.
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Water voles in history
Some interesting quotes from historical texts that refer to water voles:
“ex sergeant parker who stayed on at Isington mill as an odd job man during the last years of the Field Marshall………was said to have been attacked by a horde of infuriated water-rats when clearing weed out of the mill race – and died as a result of his injuries. ‘Most unfortunate’ was supposed to have been Monty’s callous comment”
Monty the lonely leader
"The black water vole……. feeds on frogs fish and insects and in some countries is eaten on fasting days“
Goldsmiths animated nature 1855
“When a boy at Winchester I used often to hunt rats. Having marked them to their holes sharp stakes were then thrust into the grassy banks which generally dislodged the quarry. ……The great art was at this moment to slip over his head as he swam a thin loop of brass wire tied to the end of a long stick and whisk him out of his native element to become a prey to the scholars on the bank, by some of whom, water rats skins were collected on account of their beauty and silk-like softness”.
Frank Buckland’s Curiosities of Natural History 1860.
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Water vole conservation
The water vole, once common throughout mainland Britain, has over the last few decades suffered a catastrophic decline in its British range. Without conservation action now the water vole could face a future akin to the red squirrel, becoming nothing more than a cute picture on a calendar or a walk-on character in a Victorian novelette. The factors outlined below are critical to future vole survival as a result of contemporary population fragmentation.
Insensitive management of waterside vegetation can make some sites untenable. Mowing and clearing banks can leave voles at greater risk from predators, while high densities of domestic livestock have overgrazed riparian vegetation and trample banks and burrows. Natural floodplains have been lost as result of agricultural intensification and insensitive river engineering techniques such as sheet piling reinforcements have also compromised vole habitat. Lack of river management can additionally lead to silting up, drying out or scrubbing over while both flooding and drought can have catastrophic effects.
Water voles are particularly vulnerable to predation by introduced North American mink (Mustela vison). Owing to its natural swimming ability this species can hunt voles underwater. Female mink are small enough to access water vole burrows and when nursing kits in the spring can destroy entire colonies. This predation on already fragmented populations can be devastating and as a result effective mink control is critical to water vole conservation.
More research is required on the health problems of and diseases carried by water voles. It is not yet known whether diseases such as leptospirosis, recorded in brown rats (Rattus norvegicus), can be transmitted to water voles. External parasites - ticks, mites or ringworm - can be studied by examination and testing. Faecal screening can identify internal parasites - worms and protozoa - and bacterial cultures grown for campylobacter or salmonella spp.
The effect pollution has on water vole populations is as yet unknown. Water is an essential part of their lifestyle, and when contaminated by organo-chlorine insecticides or heavy metals it is possible that this could impact on vole populations. One group of animals moved from a site polluted by heavy metals as part of a mitigation, failed to breed in captivity where there was a 95% breeding success with animals from elsewhere. This could be coincidence but further study is required in the long term to clarify this issue.
Poisoning of voles as an accidental subsiduary of legitimate rat control programmes has also been a cause of population loss. This may have been especially acute for urban vole populations.
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Water voles, development and mitigation
Water voles are currently protected under schedule 5 of the Wildlife and Countryside Act in respect of their abode. In practice this commits developers to mitigate for the results of any action they undertake, which may compromise the existence of this species. Sites likely to be inhabited by water voles must be surveyed and mitigation actions can only occur after they have been licensed.
It is a principal recommendation of the species working group that any planned mitigation should seek to retain the vole population on site and that translocations should be a final option. In order to effect this objective new habitat may have to be created to both compensate for that destroyed during development and to accommodate any displaced animals. Consideration during this process should be given to the creation of a vegetation structure which provides a suitable tapestry of seasonal food and cover in order to ensure a high quality of receptor habitat. This may entail the addition of some plant species from specialist nurseries. Other habitat features such as rough grassland retention near the water’s edge, the creation of friable burrowing banks and the likely requirement for a vole proof fence in order to prevent animals setting up territories in the newly created area prior to the movement of the target population should also be considered.
To date displacements of voles have generally relied on a process of mechanical ground scraping or strimming. Although these options may be seasonally viable on a small scale, where vole populations are low, recent studies suggest that water voles exhibit a high degree of territorial fidelity. They do not move readily in response to these strategies preferring rather to remain where they are or to try and return to their original territory if released in the near vicinity. Fencing voles out – excluding - from development areas by erecting an enclosure from weatherboard sheets may also prove fallible due to the same criteria. Water voles are excellent diggers and captive trials suggest that voles can rapidly undermine even a 2ft deep underground fence.
Riverbank development
A more promising option for displacement employing a natural behavioural response might be to retain standing vegetation and drain the available water body. Although this course of action will not be appropriate in every instance and could have implications for other scheduled species water voles will rapidly desert territories when a water supply disappears.
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Fencing water voles out and in
Water vole fencing has historically been used to either retain or exclude from a development footprint. There is little proof to support the contention that styles commonly in current use are actually effective. Fencing barriers along the side of watercourses should be of strong construction ideally sunk in sheet metal piling to a depth of 4ft. This material can be pressed in by a digger and used again or hired. It will present an un-climbable fence, which will stand water wash/pressure and deter burrowing.
Fencing on land must be sunk into the ground to a depth of 1ft for stability. The existing pattern of 8ft by 4ft plywood boards must be rendered secure by positioning half round supporting posts on the inside to prevent climbing. The fence should be at a 90-degree angle to the ground and must have no inwards slant. It must be proof against livestock – especially cattle – rubbing the outside by a removed retaining stock fence.
This style of fencing – ply boards – must have a wire mesh out-turn attached along the bottom with builders band and pegged in a curtain 1.5ft out from its perimeter into the ground. This type of fence is absolutely zoo standard for small burrowing animals and would keep voles out much more effectively than the existing pattern. The whole structure must be checked for obvious holes.
Wild captured water voles should not be retained in small fenced areas communally as this will lead directly to severe aggression, injury and death.
Fencing through a water channel is more complex and must be strong to account for water wash. Ideally sheets of heavy gauge 1inch square weld mesh – 8ft by 4ft – should be sunk to a depth of 3ft across the channel and topped with boards to prevent climbing. This design would allow for water flow through and deter effectively recolonisation. This design could also be copied for steep bankings where an alternative would be to set ply boards on end to a depth of 4ft. If practicable the best option is to temporarily bund the channel piping the water through and erecting an exclusion fence along the top of the bund.
Water vole exclusion fence
Retaining voles on site by translocating directly into new habitat where such fences have been utilised to deter re-colonisation must take into account that the habitat area for introduction must be mature from a vegetation perspective with sufficient channel convolution to ensure that animals can avoid each other. The mesh collar should be also incorporated on the inside to prevent animals quickly digging out and returning to where they came from.
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Trapping water voles
Water vole in a trap
Trapping water voles is a physically straightforward process as the species is relatively naive and can be easily captured. When water voles are fully protected under the Wildlife and Countryside Act trapping will however require a licence from the statutory authority. This will require an onus of proven competence with this species for potential applicants. Traps should be set on features such as latrines, fresh feeding piles or obviously well tracked runs. They must be checked twice daily, contain fresh straw - hay quickly becomes damp and mouldy - and a quarter chopped sweet apple – they will not eat cooking apples – for both moisture and food. It is a good idea to scatter tiny pieces of chipped apple at both the trap entrance and up the trap barrel as an inducement for animals to enter.
Traps should be set at a 45 degree angle to the potential trapping site to allow for any fluctuations in water level and secured with tent pegs to prevent predator disturbance. Trapping during the summer months should be avoided as it risks compromising the welfare of dependent juveniles underground. Female water voles have a strong maternal bond and will generally remove their offspring to a place of safety if disturbed. This behaviour has been recorded in the wild during flood conditions and is particularly common in captivity when nests of tiny juveniles are unearthed. For this reason trapping of water voles is best effected between mid September and mid April with the best times being September/October and March/April when the weather is milder. Out with this time water voles become less active as their territories contract and they become more reliant on underground caches of stored food.
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Water vole trap types
Water vole trap
The trap type employed by our consultancy has been constructed to an in-house standard based on a design used for edible dormice and red squirrels. It is constructed from half inch galvanised weld mesh with a fitted aluminium box on the back. The trap operates through the release of a door held up by a treadle arm connected to a treadle plate. This simple mechanism is unsprung to ensure that a relatively light touch will release the door. A loose clip fitted to the door bottom fits into the floor mesh when the door falls locking the trap door shut on capture. These traps are light to carry and are extremely cost effective compared to other designs currently on the market.
Other trap types, which have been commonly employed to capture water voles are the fold up American Sherman traps and the Albi trap design supplied by Alana ecology. Sherman traps are very easy to use and highly portable as they fold flat for carrying in pockets or rucksacks. They are however cramped for bedding space behind their treadles and can be quite “cold” for captured animals. The “Albi” traps most admirable feature is its detachable front barrel, which allows any captured animals to be transported virtually stress free in a dark wooden box. Most water voles captured in these traps will settle quickly and make a round ball nest. These traps are however fiddly to set; have boxes which tend to fall apart when wet and have treadle arms which are inclined to corrosion rendering the spring loaded treadle unreliable.
Our trap design is available for purchase - price on enquiry
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Mink rafts
Mink raft
The Game Conservancy Trust’s mink raft is an excellent tool, which exploits the natural curiosity of this introduced predator to identify its presence. The basic principal of the raft is that it is used initially as a monitoring tool to ascertain the presence of mink in riparian systems and their potential home ranges.
The raft retains evidence of mink presence via tracks in their central clay pad and has proven highly successful as a trapping point. At the culmination of a trapping period the rafts revert to a monitoring role. The Game Conservancy Trust has published details of precise raft use coupled with constructional details which are available on their website.
Mink raft clay pad showing signs of use by water voles
We have a local supplier who has built a number for us and can supply any required quantity fully complete and ready for use. These can be modified to incorporate otter guards as desired and have been only slightly modified by the replacement of folding hinges and split pins to retain the pad covers.
Mink raft secured at edge of slow flowing watercourse
Price on enquiry. For every raft purchased a £2.00 donation is made to Game Conservancy Trust.
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Water vole translocation
Animals should be released singly and slowly to ensure they stay put from holding cages. Release cage designs which focus on an open base allowing the animals to dig to freedom must be set into banking to a total depth of 12 inches. This leaves the lid accessible for food provision whilst securing a good digging depth for voles burrowing out. In order to delay instantaneous escape a cardboard sheet can be set in the bottom through which they will gnaw before burrowing to freedom. These cages have worked well for groups of captive bred juveniles and a recent trial at East Malling where they were fed for a month following release saw water voles coming and going from these refugia for food and using them as latrine sites. They must be filled with straw and any available old bedding, which can act as a scent drawback whilst they establish themselves.
Water voles are not easy creatures to handle. They can bite severely and if stressed for long periods on a hot day can easily die. For convenience of operation it is best to take a handling tub – fold up - round a trap site when checking traps and then to release any animals into this for further work. If removal from a site is required the best option is to move the animals in traps – after giving them apple for food and water – and then replace the trap at the capture site with another trap from a site reserve.
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The development of a captive breeding programme for water voles
In 1962 Stephanie Ryder kept and bred water voles in captivity and recounted her experiences of doing so in a delightful book published as one of a series on British mammals by the Sunday Times. In 1982 a laboratory based breeding programme for was developed by Dr Barbara Blake at Queen Mary College, London. This project contained water voles in large indoor pens constructed from aluminium. Of the 21 study pairs of animals held for this project 14 bred but infant mortality due to human disturbance was extremely high.
A conservation breeding programme for this species was not developed until 1995 at the New Forest Nature Quest by Derek Gow and Mike Jordan. This project was a response to the dramatic national decline of this species as identified from the national surveys undertaken by the Vincent Wildlife Trust in 1989/90. The aim was to create a system of captive breeding ideally capable of producing juveniles consistently in significant numbers; of holding distinct blood-lines; of catering effectively in captivity for the species needs and of replication on a cost effective basis.
Founder individuals for this programme were captured from fish farms on the river Itchen using scaled down red squirrel traps and others were added as they became available from elsewhere. The captured water voles were contained in large outdoor pens, which were landscaped to incorporate burrowing banks, concrete pools and food plant species. Their husbandry at this time was virtually unknown and attempts to maintain more than a single initial breeding pair in each pen resulted in adult females fighting severely with each other to the point of either death or disability. It became apparent that these facilities could not yield large numbers of juveniles and as a result of a grant from the Environment Agency in 1996 a redesigned breeding facility was developed.
Water vole captive breeding pen - showing swimming tray, straw bale for nesting, and fold down front
This consisted of a series of 10 pens constructed in a line utilising sheet tin again as a walling. They measured 4ft by 8ft and were entirely under-wired with heavy gauge half-inch weld-mesh. Small drainable inset troughs were fitted into the ends of each and halfway up each pen a planked barrier was constructed to retain a small bank of soil - 2ft deep by 4ft square. They were over-meshed to prevent avian or terrestrial predation and straw bedding was provided on top of the bank under the cover of a sheet of corrugated iron. Although water voles bred much more successfully in this facility significant operational flaws again emerged. The washing troughs clogged easily with soil moved around by the voles and this factor coupled with the natural tendency of this species to defecate in water meant that they were laborious to maintain. As a result of the forgoing a different design of more flexible, cheaper, mobile pens were developed.
The pens now currently employed to breed water voles are constructed from inch and a half timber over wired with half-inch pet mesh. Their dimensions are 4ft wide by 6ft long by 4ft high with the front section together with the roof being a half lid structure to enable easy access. The floors are constructed from half inch boarding or ply over meshed again with half-inch weld to prevent gnawing. When in use these cages are floored with wood bark and a straw bale covered with bitumen soaked roofing card is provided as a nesting facility. Shallow water trays are set into the front of the enclosure and these are changed daily depending on the seasonal stocking density. Water voles thrive on a standard alfalfa based rabbit mix coupled with a daily provision of fruits (apples, pears, melon) and vegetables (brussel sprouts, cabbage, carrot, broccoli, kale, parsnip and sweet corn).
Captive bred young voles
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Water vole future
The future survival of the water vole in Britain is closely linked to the re-creation of well-vegetated wetland ecosystems, which have been commonly destroyed in the past by agricultural or land drainage activity. Recent research suggests that large non-linear wetlands provide water voles with such ideal living conditions that they can - even in the presence of mink – consistently produce a population surplus sufficient to re-colonise adjacent waterways to a length of several kilometres. A conservation process similar to that already underway in Holland which seeks to create wetlands from existing agricultural land could well have a significant role to play in securing the future of the water vole in Britain.
It is for this reason that the personnel of the Derek Gow Consultancy have encouraged through media campaign and practical activity the reintroduction of the European beaver (Castor fiber) to Britain for their excellent wetland creation abilities. Derek has imported over 30 European beaver to date from Poland, Germany and Norway to form a captive breeding population in the UK. As a result of this activity an effective protocol has been developed to cater for the statutory 6-month rabies quarantine this species must undergo and continental techniques for gland-secretion sexing, handling, transport and trapping have been perfected. Derek project-led the import/quarantine of Norwegian beavers for Kent Wildlife Trust’s ‘Ham Fen’ project and has recently imported beavers for two private landowners in Scotland and the Cotswolds.
European Beaver
European beaver were hunted to virtual extinction throughout Europe for their pelts, casotreum – a secretion in their anal glands - and occasionally for meat. Although once widespread in Britain this same process of persecution rendered beaver extinct in England by the early middle Ages. It is possible that they survived in Scotland until the 16th century.
European Beaver are generally larger than their Canadian (Castor Canadensis) counterparts but both species are excellent wetland engineers whose damming abilities are legendary. Beavers are extremely good swimmers and commonly build dams on narrow water-courses to provide an easy means of access to bank-side vegetation and a moated security system for their lodges. The variety of pools and waterways created as a by-product of this “Keystone” activity provides a wealth of habitat for a host of associated wildlife. Otters for example will readily utilise abandoned beaver lodges as holts and extensive research demonstrates clearly that beaver created wetlands are much richer in associated life - amphibians, aquatic plants, fish, invertebrates and birds – than riparian systems with no beavers.
It is for this prime reason that European beaver have been restored to every other European nation in Western Europe barring Britain and Liechtenstein.
Although the possibility of restoring beaver to Scotland has been seriously considered be Scottish Natural Heritage there is no good reason why the reintroduction of this species should not be advanced for England and Wales.
Beaver & Young
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