Chapter 14 Practical techniques

Practical techniques: Otters

Practical techniques: Otter

UK and Ireland

The otter (Lutra lutra) is found throughout the UK and Ireland and is associated with streams, rivers and coastal areas. Otters prey mainly on fish and have large home ranges, extending over tens of kilometres. The breeding and resting places used by otters (known respectively as holts and couches) can be anywhere the otter is unlikely to be directly disturbed, such as in dense vegetation, under tree roots, or amongst rocks. Otter numbers declined rapidly during the 1960s and 1970s, and they became extinct in many areas of the UK. Pollution was the most likely cause of this decline. In recent years otter numbers have begun to recover, as river water quality has improved and otters have been recorded in every region of England, and every county.

Protection and its implications

The otter is listed under Annex II of the Habitats Directive and therefore EU member states are required to designate Special Areas of Conservation to protect important populations of this species. These sites are protected under the regulations derived from the Habitats Directive, as described earlier in the Handbook.

Even outside of designated sites, otters and their holts are fully protected. As a result of their full protection under the regulations derived from the Habitats Directive, mitigation for otters on development sites is governed by a strict licensing procedure administered by the appropriate statutory agency. A licence will be required whenever disturbance of otters or damage to their holts is likely to occur.

In all the devolved administrations of the UK, the otter is listed as a priority species. Government policy is that local planning authorities should consider such species when determining planning applications.

In common with most protected species, the presence of otters can lead to planning permission being refused unless the applicant can clearly demonstrate that they will be adequately protected during the development process, that disturbance is kept to a minimum, and adequate alternative habitat is provided to sustain at least the existing population. As otters are a European protected species, it will also be necessary to demonstrate that the tests in the Habitats Regulations can be met at the planning application stage.

Otters are present on waterways throughout the UK and Ireland and so any development that affects a watercourse or is alongside a water course could affect them. However, otters are not confined to the watercourse and its banks but may shelter several hundred metres away. If it is possible that otters are using a site, then care must be taken when planning any activities that could have an impact on otters themselves or places where they shelter.

Mitigation techniques

Protection of individual otters

As otters are wide-ranging and highly mobile they may be simply passing through a development site close to water from time to time. For this reason a few modifications to site practice and layout may be sufficient mitigation: for example, locating site compounds away from potential otter habitat (such as wooded stream and river banks), avoiding night working involving flood lights and noisy machinery, excluding construction workers from sensitive areas, and using fencing to delineate a safe route for otters through the construction site. Particular care must be taken to avoid encouraging otters on to roads, as traffic mortality is a significant threat to otter populations.

If the destruction of an otter holt or potential otter holt is necessary, it must be carried out when the otters are not present. The area surrounding the holt or potential holt should be fenced to discourage otters from returning and the holt cleared cautiously and under the supervision of an ecologist. If the holt is used for breeding, then it may be necessary to wait for 10 weeks or more until the cubs are able to leave.

The construction of new roads which cross rivers and streams is a particular problem for otters. Poorly designed culverts and bridges can force an otter to cross the new road and risk being killed. To combat this, new watercourse crossings should be designed to allow safe passage for otters underneath the road. An open span bridge is the ideal solution, however oversized culverts with ledges above the water level or parallel otter tunnels can also help prevent road deaths. These measures should be combined with otter-proof fencing alongside the road.


Maintaining habitats for otters

Ideally, the planning of a new development would include a zone of undeveloped land alongside the river to allow safe otter passage and protection of areas of dense cover, such as reed beds, tall grasses, woodland, scrub and natural or artificial rock piles within 500m of a watercourse, which may be used by otters for shelter.

If holts or potential holts are affected by the development, it is possible to replace these with artificial holts made from logs or rocks. The creation of undisturbed dense cover such as reed bed and scrub may also benefit otters. Maintaining good environmental site practice following the Environment Agency’s (UK) Pollution Prevention Guidelines (now officially withdrawn) or advice from the Environmental Protection Agency (Ireland) should ensure that there are no significant impacts on otters as a result of pollution during construction. Measures designed to protect and enhance the aquatic environment should generally also benefit otters.


Monitoring of otter signs may be required after the development, with the length of the monitoring period being appropriately related to the size of the development and the disturbance caused. Monitoring of river water quality may also be appropriate in some situations. Fish surveys could be considered if management practices aim to increase fish stocks for otters.

Timing of works

Works affecting otter habitat are not seasonally constrained by the presence of otters since they do not hibernate and they breed throughout the year. Construction activities may have to wait until otters have finished breeding if this occurs on or near the development site.

Further reading

Chanin, P. (2003) Monitoring the Otter (Lutra lutra). Conserving Natura 2000. Rivers Monitoring Series No 10, English Nature, Peterborough.

Liles, G (2003) Otter Breeding Sites, Conservation and Management. Conserving Natura 2000 Rivers Conservation Techniques Series No. 5. English Nature, Peterborough.

Natural England, Forest Research and Forestry Commission (2013) Guidance on managing woodlands with otter in England.

Northern Ireland Environment Agency (2011) Otters and Development, NEIA.

Natural England (2015) Otters: surveys and mitigation for development projects.

Chapter 14 Practical techniques
Thomson Handbook Chapter 14 Practical techniques Practical techniques: Otters