Species Biodiversity Action Plans (Summaries)

Species Biodiversity Action Plan - Otter

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Common name: European otter
Scientific name: Lutra lutra

Description

The European (or Eurasian) otter is the only species of otter native to the UK, and is one of our largest animals, living in both fresh and salt water environments.

They generally have brown fur with a pale underside, a long slender body, small ears, a long thick tail, webbed feet and a flattened head. The head and body length is around 60 to 120cm, with a tail length 40 to 45cm, and the average weight is about 10.1kg for the male and 7kg for the female. They are a carnivorous species, the adults of which consume around 1km of food per day, over 80% if which is fish (the type of fish being dependent on availability) although they will also eat amphibians, birds, molluscs, crustaceans and small mammals.

A typical range will encompass a river, side streams and ponds together with the adjacent woods and wetlands. However, the size of the range can vary from 1.1km on coasts with a rich food supply to 40km on rivers (dependent on the quality of the habitat, food supply and social interactions with neighbouring animals). A range will also generally contain a number of holts or dens (although otters will also lie up above ground), which can take several forms including cavities in the roots of bankside trees, piles of logs or flood debris and caves in rock falls, the most secure sites being used for breeding. Otters commonly deposit faeces (known as spraints) in prominent positions within their territory in order to mark the extent of their range, and help heighbouring animals keep in contact with each other.

Breeding can occur at any time of year, but the majority of cubs are born (in litters of between one and four cubs) in the spring or summer when there is a greater chance of survival. Cubs take their first swim at about three months old, but don't become independent until about one year old; consequently females are restricted to breeding every one or two years.

Legal Protection

  • The otter appears in Appendix II of the Berne Convention (Convention on the Conservation of European Wildlife and Natural Habitats). This requires that they be strictly protected against deliberate killing, capture, damage/destruction of breeding and nesting sites, disturbance, trading (including parts and derivatives), etc.
  • They are also protected under Appendix 1 of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) which is enforced in Britain by the Control of Trade in Endangered Species (Enforcement) Regulations 1997. This is intended to protect species considered to be in danger of extinction, and (in the main) prohibits trade in them (together with any recognisable part or derivative).
  • Under Annex II and Annex IV of the European Communities Council Directive on the Conservation of Natural Habitats and Wild Fauna and Flora, which covers species of community interest that are in need of strict protection. Damage or destruction of breeding sites or resting places is prohibited, and all life stages are protected against deliberate capture, killing, disturbance or destruction in the wild; and keeping, transport, sale/exchange and offering for sale/exchange of specimens, and scope is provided for the designation of Special Areas of Conservation (SACs).
  • Under domestic legislation, otters are covered by the Wildlife and Countryside Act 1981 (as amended). Under Schedule 5, the deliberate killing, injuring, taking, possessing, disturbing and selling (including parts and derivatives) as well as damaging, destroying or obstructing any structure or place of refuge etc are prohibited. Under Schedule 6, certain methods of killing or taking animals are specifically prohibited, and even humane trapping for research requires a licence.

Current Status

The otter was formally considered to be widespread and common throughout the UK, but between the 1950s and 1970s, it underwent a rapid decline in numbers, effectively being lost from much of central and south-eastern England by the 1980s. However, populations remain in Wales, south-west England and much of Scotland, where sea loch and coastal colonies comprise one of the largest populations in Europe. There is also a sizeable population in Northern Ireland. In recent years the decline in numbers would appear to have been halted, and the species is now making a recovery, moving into some of its previous habitats.

Threats and Issues

  • Pollution of watercourses - particularly in the form of organochlorine pesticides (especially PCBs), that bio-accumulate in the fish eaten by otters; and more recently the synthetic pyrethoids present in sheep dips. Small populations are particularly vulnerable to isolated pollution events.
  • Drought - either natural or induced by over abstraction.
  • Reduced prey - this can also associated with poor water quality, although a parasite problem in the eel population and eel harvesting also contribute to the problem.
  • Poor bankside habitat - a lack of the habitat features required for breeding.
  • Incidental mortality - mainly in the form of road deaths and drowning in eel traps.
  • Hunting and trapping of mink - may inadvertently kill otters instead.
  • Fishing - there is a perceived conflict with angling/fishing that can result in the deliberate killing of otters.
  • Developmental pressures - otters often require a large range, something that is not consistent with the pressure for urban expansion (which can result in the fragmentation of habitats).
  • Disturbance - by recreational users of the countryside.

Objectives (as pertinent to agriculture)

The national species action plan specifies two objectives:

  • To maintain and expand existing otter populations.
  • By 2010, to restore breeding otters to all catchments and coastal areas where they have been recorded since 1960.

Conservation Advice

1) Habitat management

  • Habitat type - otters require a habitat consisting of unpolluted watercourses, bankside trees (with exposed horizontal root systems) and vegetation to provide cover, they also require a plentiful supply of food (such as eels) if the population is to be self-sustaining. Hollow trees, piles of logs, dead wood and brashings are also useful as resting places and holts; and scrub and tall bankside vegetation, reed and sedge beds, small watercourses, lakes, ponds oxbows and mid-channel islands all provide valuable habitats.
  • Grazing and mowing - these processes remove cover and are therefore damaging to otter habitats. If grazing is to occur allow only one bank to be grazed and where possible fence off short sections of river bank to allow vegetation growth. When mowing is to be carried out, areas of uncut vegetation should be left or alternatively one bank should be left uncut. The cutting regime can be varied annually to prevent the growth of woody scrub, whilst still providing cover for otters.
  • Channel management - Dredging should be carried out from one bank only, and only 2/3 or less of the channel width should be dredged. Particular care should be taken when dredging small watercourses or ditches, since these are of great importance to breeding females, which are highly susceptible to disturbance.
  • Bank maintenance - if bank regrading is essential, it should be restricted to small sections of watercourse, and the new profile should maximise the width of marginal vegetation that can re-establish itself. If reinforcement is required, the use of small scale repairs based on living willow withies, coir fibre bundles or other natural materials is encouraged. Tree planting will also help to bind bank material together, due to their root structure.
  • Tree and scrub maintenance - the cover provided by trees and scrub should be maintained or restored, but if scrub clearance is necessary it should be carried out as late as possible in the year and only one bank should be cut in any one year in order to maintain a continuity of suitable habitat. Similarly, coppicing of woodland in blocks on a rotational basis is also good practice; and the coppicing or pollarding of trees adjacent to watercourses is preferable to removal.
  • Tree and scrub planting - Planting trees on or near a watercourse may require land drainage consent, so the Environment Agency should be consulted at an early stage. In general however, planting native species such as hawthorn, blackthorn, dog rose and bramble can provide good cover for otters, and oak and ash can provide good holt sites once mature. Better cover is provided if clumps of trees (perhaps in field corners) are planted.
  • Wetlands - these should be managed in order to retain high water levels and sufficient cover vegetation.
  • Fencing - this can be used to prevent over grazing by livestock, allowing vegetation to regenerate. Fencing off meanders is an effective way of providing valuable otter habitats with the minimum use of fencing.
  • Holts - building log pile and pipe and chamber holts can supplement natural holts in areas of suitable habitat. They should be situated within large complexes of waterside and wetland habitat, where they are fairly safe from flooding and disturbance.
  • Bridges and culverts - otters are often forced to cross roads when routes under bridges and culverts are blocked at times of high flow, the provision of 'underpasses' for otters to use can significantly reduce road casualties.

2) Re-introductions

The re-introduction of otters to their past range is a difficult process, although it has been successful in some cases. Captive breeding programmes have been set-up by the Otter Trust and various other sanctuaries and parks, and can be used to supply stock, but because of the protected nature of the species and the difficulties involved, no re-introduction programme should be established without the involvement of a suitable body (English Nature, Countryside Council for Wales or Scottish Natural Heritage ).

References and Further Information

Andrews, J. and Rebane, M. (1994). Farming & Wildlife: A Practical Management Handbook. The Royal Society for the Protection of Birds, Sandy, UK.

Betts, C.J. (1998). Checklist of Protected British Species. Christopher Betts Environmental Biology, Worcester, UK.

Flowerdew, J.R. (1997). Mammal Biodiversity in Agricultural Habitats. In: Biodiversity and Conservation in Agriculture: Proceedings of a Symposium held at The Stakis Brighton Metropole Hotel 17 November 1997, (Ed. Kirkwood, R.C.), pp. 25-40. British Crop Protection Council, Farnham, UK.

National Rivers Authority. (1993). Conservation Technical Handbook 3: Otters and Habitat Management. National Rivers Authority, Bristol.

The Mammal Society. (1997). Fact Sheet No. 6: The Otter Lutra lutra. The Mammal Society, London.

UK Steering Group. (1995). Biodiversity: The UK Steering Group Report, Volume 2: Action Plans. HMSO, London.

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