Otters at Colyford Common (Photo from Ian McLean)
Otters at Colyford Common (Photo from Ian McLean)

 

Common names

European otter, Eurasian river otter, common otter, old world otter

Scientific name and classification

Order Carnivora
Family Mustelidae
Sub-family Lutrinae
Genus and species Lutra lutra

Otters are members of the Family Mustelidae, carnivorous mammals including badgers, weasels, martens, polecats, stoats, and mink. All mustelids have well-developed musk glands at the base of the tail. The Mustelidae has five sub-families including the Lutrinae, to which otters belong. Of 13 known species of otter worldwide only one is native to Britain – the European otter (Lutra lutra).

The word otter derives from the Old English word otr or otor and the Middle English word oter. It stems from the same root as the words water, wet and winter. Cognate words include the Old High German ottar “otter” and the Greek hydor “water”. Lutra derives from the Latin for otter.

Conservation/protected status

  • International: IUCN status: 2008 classification as Near Threatened
  • European: a European Protected Species under Appendix II of the Bern Convention, incorporated into UK national legislation as the Habitat Regulations 1994 Schedule 2 (and under the subsequent Habitat Regulations 2010) 2010 and the Directive on the Conservation of Natural Habitats and of Wild Fauna and Flora (Habitats & Species Directive) Annex IIa and IIIa
  • National:
    • Schedule 5 species listed under the Wildlife Countryside Act 1981 (as amended)
    • A Species of Principal Importance under the NERC Act 2006
    • Biodiversity Action Plan priority species: in the national, regional, Devon BAP, and also in Local BAPs in Dartmoor, Exeter, Teignbridge and others

In 1978 the connection was made between the decline in otter populations and the widespread use of organochlorine pesticides in farming. As a result, otters were given full legal protection under Schedule 5 of the Wildlife and Countryside Act 1981 (as amended by the Countryside and Rights of Way Act 2000). It is an offence to intentionally kill, injure or take an otter from the wild; possess live or dead animals or any parts thereof; damage, destroy or obstruct access to any place used for shelter or protection by an otter or to disturb an otter whilst it is using such a place; sell, possess or transport for the purpose of sale any live or dead animal or part thereof.

The otter is a European Protected Species under the Convention on the Conservation of European Wildlife and Natural Habitats (Bern Convention) Appendix II (special protection for listed animal species and their habitats) and the Directive on the Conservation of Natural Habitats and of Wild Fauna and Flora (Habitats & Species Directive) Annex IIa and IIIa (designation of protected areas for animal and plant species listed).

The otter is listed as a Species of Principal Importance under the NERC Act 2006 and on the UK Biodiversity Action Plan as a priority species (one that is globally threatened and rapidly declining in the UK) and has a Species Action Plan. It has also been identified as a species of key conservation concern in Devon and has a Devon Biodiversity Action Plan.

Current and local status

Devon has always been a stronghold for otters, but during the 1950s and 60s populations crashed. By the 1970s, otter numbers had fallen by 75% in Devon and by 90% in other parts of England, with complete populations wiped out in some areas. In the 1970s and 1980s it seemed a realistic prospect that otters could become extinct in this country. The cause of the devastation was found to be mainly due to water contamination by chemicals used for intensive farming and industry. Organochlorines and other chemicals were leaching into rivers and streams, poisoning fish, killing some otters outright and causing others to become infertile.

Fortunately, this massive decline in the otter population was noticed in time, significantly by otter hunters, and steps were taken to reverse it. Many pesticides were phased out and, gradually, water quality improved and fish stocks increased. Otter hunting was banned in 1979 in Wales and England and in 1982 in Scotland, and the otter was afforded full legal protection.

Since then, otters have made a remarkable comeback and today are found in good numbers throughout Cumbria and the West Country. Up to the 1980s re-introductions were carried out in other parts of England, but this is not current policy; current conservation action would be to improve riparian habitat so that otter recovery and expansion occurs more naturally. Re-introduction in the south west, where a native population persisted throughout the period of decline, would not be advocated.

Otter populations have recovered to the extent that the last National Otter Survey 2009-10 found signs of otters in nearly all of the sites looked at in Devon. Otters are considered to be present on each of the county’s main watercourses with most if not all available territories occupied. Results from the 2009-10 national survey suggested that Devon and Cornwall were the only counties in England where populations had recovered to close to pre-decline levels.

General description

BODY Long, lithe and streamlined with a long neck.

HEAD Flat, with a broad muzzle. The muzzle of the dog otter is broader and thicker than that of the bitch. Ears are small and rounded. Eyes and nostrils set high on the head enable the otter to see and breathe when the rest of its body is under water. When the otter submerges, valves close to protect its ears and nose.

The eyes are forward-facing and an adjustable curvature of the lens allows the otter to see clearly underwater in bright light. When an otter submerges, its ears and nose are protected by valves and it is able to drink with its head completely underwater.

The muzzle is surrounded by long, stiff, sensitive whiskers, or vibrissae, which help the otter locate prey in the dark or in murky waters.

The otter has sharp teeth for biting and chewing. Long, backwardly curved canine teeth are used to impale and grip prey and large back teeth are used to crush bones and chew flesh.

LEGS Short legs with webbed feet. Each foot has five toes and blunted, curved claws.

TAIL Thick, muscular rudder that is slightly flattened at the base and tapered towards the tip. The otter uses its tail to help it move and steer in water.

COAT Medium to dark brown in colour above, lighter underneath, and sometimes pale at the throat. The otter’s coat has two types of hair; a dense undercoat of fur that trap an insulating layer of air and remain dry when the otter is swimming, and a waterproof outer coat of longer, coarser guard hairs. When wet, the coat looks darker; and as the otter leaves the water, its guard hairs aggregate into small tapering bunches, giving the animal a spiky appearance.

SIZE Adults one metre long from nose to tail. Dog otters are distinctly larger than bitch otters.

MOVEMENT On land, otters bound and appear heavy footed, but can run quickly, if required. Over short distances they can run as fast as a man. In water, the streamlined otter is an agile and graceful swimmer. When swimming slowly or at the surface, the otter uses all four paws in dog-paddle fashion. When accelerating or swimming underwater, it tucks its forelegs against its body and moves its hind legs in powerful strokes, flexing its hind end up and down to propel itself through the water at high speeds.

SENSES Well-developed vision, excellent hearing and an acute sense of smell. These keen senses, together with the otter’s natural curiosity and sharp instincts, help to make it an expert hunter.

SCENT GLANDS Both dog and bitch otters have two scent glands in the muscle of the anal region. These glands produce small quantities of liquid which the otter uses to mark its territory as part of its communication system.

Habitat

Otters are solitary, territorial animals, nearly always found beside water. They mainly live along rivers, but are also found in and around canals, marshes, ponds, lakes, ditches, streams, and estuaries and along coasts.

TERRITORIES Although otters travel large distances, most adults stay in a well-defined territory in which they feed, rest, and reproduce. Otter territories are measured as lengths of river bank or coast. The sizes of individual territories depend on the quality of habitat, amount of food and number of holt sites available. Dog otters have much larger territories than bitches. A dog otter may cover about 18km (12 miles) of the main river whereas a bitch may use about 11km (7 miles). Significant lengths of this territory range may be covered in one night’s travelling. One male otter’s territory generally overlaps those of several females. Otters patrol their beats constantly and defend their territory by fighting. In Devon, the otter population is close to carrying capacity so competition for new territories is fierce. Dog otters are known to kill and eat other young males. Territorial behaviour in otters helps to control population density by spacing out individuals. It also avoids over-exploitation of food resources.

HOLTS Otters rest in underground dens, called holts, under waterside trees or in old rabbit burrows or in cavities in bank-side rocks. They can be up to 10 meters underground and may have underwater entrances. Mature trees, particularly those with well-developed root systems, leaning trunks and overhanging branches provide ideal holt sites. Ash trees and sycamore trees are important sites for otter holts as both have shallow spreading roots which make ideal roofs for holts.

COUCHES Otters also use above-ground resting places, called couches, built on the banks of a river, stream or lake, and occasionally further inland, often in thick vegetation or reed beds. Rolling places, where the otter dries and grooms its fur after leaving the water, may also be used as couches.

General behaviour

ACTIVITY Otters are largely nocturnal and seldom active during the day. Much of their time is spent hunting, travelling and patrolling their territory.

HUNTING AND FEEDING The otter is an active and opportunistic hunter. It searches and explores weed beds and tree roots along the water’s edge, taking whatever is easiest to catch or most abundant. Its diet consists primarily of fish, but may also include frogs, crustaceans, molluscs, birds and even small mammals. Eels are a favourite food and, wherever they are plentiful, form a substantial part of the otter’s daily food.

The otter’s diet varies according to the time of year and place and depends on what species are available. In winter, as the water in streams, rivers and lakes cools, cold-blooded fish slow down and become easier to catch; eels bury themselves in mud, and are dug out and caught. In spring, as the waters warm and fish become more active and difficult to catch, the otter hunts for frogs, crustaceans, and young waterfowl in unguarded nests. Analysis of fish bones in spraints suggests eels are a main component of diet. Otters may seasonally move to headwaters and upland marshes to hunt for spawning frogs and may follow runs of salmon and sea-trout upstream. Coarse fish such as roach, perch, pike, bream, rudd, and tench are also taken, and otters living near the sea hunt for crabs and for bottom-dwelling fish such as flounder, butterfish, and pollack.

GROOMING Regular grooming keeps the otter’s coat in good condition, essential for water proofing and heat regulation. After swimming, it dries itself by rolling on the ground and rubbing against logs or vegetation. It uses its teeth and claws to remove dirt and debris from its fur and smears oil from sebaceous glands onto the fur to retain the waterproof barrier of its outer coat. Grooming may also remove parasites. Coat maintenance is such an important factor that coastal dwelling otters must have a source of freshwater nearby; this may then influence habitat selection and distribution.

BREEDING Otters are largely solitary with males and females having close contact only for courting and mating, the male playing no part in rearing the resultant cubs. From captive breeding and zoo animals, breeding can occur throughout the year but it is not known if this is generally the case in the wild. There would be an advantage in timing birth to the start of the most productive seasons of the year.

It is thought otter bitches can breed once every two years. After nine weeks of gestation, the bitch gives birth in a secure holt lined with grass, reeds, twigs and other vegetation. Litter size ranges from one to five cubs, but two or three are the norm. The cubs are born blind and helpless but fully furred.  At four to five weeks, the cubs’ eyes open and at 10 weeks they emerge above ground with their mother. At seven weeks the cubs begin to take solid food and by three months they are weaned but still dependent on their mother to catch their food. From four months of age, the cubs accompany their mother on hunting expeditions and learn fish. They stay with her for about a year, during which time contact is very close. Eventually, at around 12 months, the family splits up and the bitch begins her reproductive cycle again. The cubs are now on their own but stay in their mother’s territory for another few months until they gain confidence to travel further afield in search of a territory of their own.

SOCIAL BEHAVIOUR The otter is territorial and solitary with an inbuilt wanderlust. It feeds and moves on. This urge to wander prevents overcrowding and overfishing in any particular pool or stretch of the river. Dog otters and bitches with cubs keep to their own separate territories which they defend aggressively. Adults have close contact only when courting and mating.

COMMUNICATION An otter’s spraints, impregnated with scent and left at conspicuous places along its territory, are an important form of communication with other otters and help avoid aggressive encounters. When fresh spraints of a territory-holding otter are encountered by an intruder, they serve as a warning: “Go away or risk being attacked”.

Being solitary animals and stealth hunters, otters tend not to vocal communications and are generally silent. Nevertheless, several different calls are used for short-distance communication. Vocalisations include a high-pitched, one-second ‘whistle’ usually between a bitch and her cubs; bird-like twittering noises by young cubs, and squeaks and cat-like noises during play-fights. Other calls include a greeting ‘whicker’, a threatening ‘chitter’, and a loud ‘hah’ uttered when the otter is startled.

Life history traits

POPULATION PROFILE A population of otters comprises territory-holding solitary adult males, family groups led by adult females, plus individuals with no home base. Otters without a territory include yearling cubs who have recently separated from their mothers, and unmated adolescent males and females of two to three years. These homeless individuals live a transient existence, often in sub-optimal habitats. Otter spraint is sometimes found on the high moors which otters may use to get from one river catchment to another; Cranmere Pool on Dartmoor is close to the watersheds of three main rivers, the Dart, the Taw and the Okement. During their wanderings, young otters gain strength and experience, search for and explore new habitats, check scent marks, test territory boundaries and eventually, if they survive, establish their own territory. For otters to spread into new areas, it is suggested that males are highly itinerant, and it is only after females have set up home ranges that breeding takes place and a population becomes established.

AGE AT MATURITY Both male and female otters normally reach maturity by the time that they are two years old.

LIFE EXPECTANCY Otters can live to be ten years old, though few survive more than four or five years in the wild. Otters are not able to breed until they are around two years old and cubs stay with their mother for up to 18 months, so a bitch is unlikely to rear more than two litters in her lifetime. When cubs leave their mother they are at their most vulnerable and the mortality rate is highest at this time.

The short life expectancy of wild otters combined with late sexual maturity result in slow population growth. Whilst many threats facing otter populations are well known, the full explanation for this short lifespan is not fully understood.

Post mortem studies (which necessarily have analysed only those carcasses recovered, so to some extent represent a biased sample) suggested traffic deaths are a key mortality factor, and that there are peak periods for these, namely winter, when river levels are high, forcing otters to cross over, instead of under, bridges. An additional mortality factor appeared to be injuries from direct aggression between individuals, which might be associated with territorial behaviour.

Where to see otters in Devon

Distribution of otters in Devon
Distribution of otters in Devon

Otters are found on all of Devon’s major rivers.

The River Axe rises in Dorset and flows round the edge of Somerset before reaching Devon. Regular recent surveys suggest that from eight to eleven otters customarily live in the Axe catchment.

The River Culm rises in the Blackdown Hills and flows southwest across Devon to join the River Exe near to Exeter. Like other Exe tributaries, the Culm’s otter population is increasing.

The River Dart winds its way down from Dartmoor to Dartmouth on the South Devon coast. The Dart is an otter stronghold, with territories believed to cover its entire length.

The River Exe flows for more than 50 miles, through Tiverton and Exeter and into the sea at Exmouth. Otters are found along the main river and on its tributaries. In summer 1999, Devon Mammal Group and Devon Wildlife Trust surveyed the city of Exeter and found more than 100 otter signs right through the heart of the city along the River Exe and the canals. This survey was repeated by DMG in 2010 through a partnership with Exeter City Council and Ambios. Otter signs were found along  the main River Exe corridor as previously, with further consolidated use of smaller tributaries such as the Alphin Brook and the North Brook.

The River Otter starts its south-westerly journey to the sea from across the county border in Somerset. After decades of decline, otters have made a good comeback on the river. The settlements Ottery St Mary and Otterton may be named after the river rather than the mammal, though the etymologies are probably linked, a factor not overlooked by the local Otter Brewery.

The River Plym rises on Dartmoor and flows south to Plymouth. Previously isolated otter populations are now breeding successfully on the Plym.

The River Tamar is 50 miles long and is a natural boundary between Devon and Cornwall. Otters frequent the whole length of the river.

The River Taw flows from Dartmoor to Barnstaple on the North Devon. The Taw, together with the River Torridge, featured in Henry Williamson’s Tarka the Otter and is once again home to a population of otters. The Museum of Barnstaple and North Devon has a special room devoted to Tarka, which is well worth a visit.

The River Teign winds its way down from Dartmoor to Teignmouth on the South Devon coast. Otter numbers are increasing along this beautiful river. Otter signs are infrequently found around the urban areas of Newton Abbot, where the river is joined by the rivers Lemon, Bovey, and Aller, emptying into the Teign Estuary.

The River Torridge rises at Baxworthy Cross and travels in a loop before joining the River Taw at Appledore and flowing into the Bristol Channel. The Torridge catchment supports one of the best otter populations in England.

Otters are present on all of Devon’s rivers but are notoriously elusive and difficult to glimpse. Scientists who spend years studying the otter seldom see one in the wild. Otters are nocturnal, nomadic, semi-aquatic and secretive. Their finely tuned senses mean that they almost certainly will be aware of your presence before you see them, and they will be gone.

You may not be lucky enough to see a wild otter but the following accessible areas, where otters are known to visit, are good places to look for field signs of otter activity.

BEAM WEIR, near Great Torrington

Made famous in Henry Williamson’s book Tarka the Otter, the riverbank near Beam Weir was described as Tarka’s birthplace, and much of the BBC film On The Trail of Tarka was made at this location. Beam Weir is frequently visited by otters. Above the weir, a footpath and cycle trail crosses the River Torridge three times in less than half a mile, each bridge giving good views of typical otter habitat.

OS map reference: SS474205

HALSDON NATURE RESERVE, near Dolton

Devon Wildlife Trust’s nature reserve at Halsdon is a significant site for otters. Buried in a steep-sided, wooded valley, the reserve overlooks the River Torridge. It is a Site of Special Scientific Interest comprising 57 hectares of deciduous river valley woodland, riverside meadows, marsh and river. Otters are sometimes seen from a hide overlooking the river.

OS map reference: SS554131

TOTNES WEIR

Totnes Weir on the River Dart separates the freshwater from the tidal stretch of the river that winds down to the sea at Dartmouth. The sandbank below the weir is a gathering place for gulls, geese and wildfowl. Alongside the weir is a salmon ladder, fished by heron, and the weir pool is visited by migrating sea trout. Otters have been spotted along the banks of the river and spraints can often be found.

OS map reference: SX800612

SLAPTON LEY

Slapton Ley, which includes a large natural lake separated from the sea by a narrow shingle bar, is a National Nature Reserve and Site of Special Scientific Interest. The reserve’s marshes, reed-beds and woodland provide a variety of habitats for the birds, fish, eels, dormice and badgers. Otters are found here, and tend to stay at the back of the ley, away from human contact. The Field Studies Council Field Centre at Slapton village has maps and information about the area and a circular nature trail walk provides good wildlife viewing areas.

OS map reference: SX823441

AXE ESTUARY

The River Axe traces the Somerset and Dorset borders in the east of the county. Axe estuary is a nature reserve managed by East Devon District Council between Seaton and Axmouth on the coast by the Devon-Dorset border. The reserve is important for shore birds so there is no access to sensitive open tidal areas. However with this protection from disturbance, resident otters have become used to being openly active during day time, first seen in 2009. They can sometimes be viewed from the reserve’s bird hide and have also been spotted from trams travelling along the Seaton – Kingsdon tramway, which passes between Seaton Marshes and Axe Estuary nature reserves.

OS map reference: SY252905

EXETER, Countess Wear and Double Locks

The River Exe passes through a pinch point at Exe bridges, a canalised stretch under the central roundabout in the city with no vegetation cover. Interestingly otter signs are sometimes found alongside the smaller brooks and leats that connect to the main river. There have been rare sitings of otters from the Mill on the Exe pub garden, near the Millennium bridge. Since 2009 otters signs have been found, and otters regularly filmed, by cameras placed under Devon Wildlife Trust’s Cricklepit Mill, near Exeter quay. Signs can sometimes be found around Riverside Valley Park south of the city centre, and an otter has been spotted visiting the allotments by the river.

OS map reference: SX916921

Downstream. the ancient Countess Wear bridge is the lowest crossing place on the tidal River Exe. An easy two-hour circular walk on good, flat paths, starts from the wharf at Exeter and crosses wetlands, canal and river bridges, leats and woodlands. Grey mullet can be seen from Ducks Marsh Bridge and snipe, heron and dragonflies around wet grasslands near Double Locks. Otters are known to frequent this area and have been seen on rare occasions from the canal path.

OS map reference: SX939899

Common survey techniques

Because otters are largely nocturnal and elusive, direct observations are difficult and surveys are based principally on the observation and recording of spraints. Finding spraint is the most commonly used survey technique. This can be used mainly to reveal presence, though not finding any spraint need not denote absence of otters. Tracks, when clear, can also provide definitive evidence of presence.

SPRAINTS Otter droppings, or ‘spraints’, consist almost entirely of undigested fish bones, scales, feathers, small animal bones and insect particles, held together by black, tarry mucous. Spraints vary in size from a tiny blob or smear of tar to a compact, tubular dropping up to 6 cm long. Fresh spraints have a characteristic sweet-musky smell, often said to be like jasmine tea. This smell is the most reliable diagnostic feature for identifying otter droppings. As spraints age, they dry out, turn grey and crumbly, and gradually lose their scent, though old spraints can retain some of the distinctive smell for over a year. Mink droppings (or ‘scats’) smell very unpleasant. Another deposit very occasionally found is anal jelly, a clear – translucent gel, which does not contain bone fragments, and which also bears the characteristic ottery smell. A very rare find would be milky spraint produced by cubs.

Because spraints are a form of communication, they are left in prominent places where they can easily be found by other otters. Look for spraints by rivers and streams on rocks and boulders, fallen tree trunks, logs, on concrete ledges under bridges, and on otter paths especially where the animal leaves and enters the water. Spraints are often left where a side tributary joins the main river.  Where there are no such obvious locations, a trick might be to provide a strategically-positioned rock, brick or other suitable object for otters to use (obtain landowner permission for this, as appropriate).

TRACKS An otter’s footprint has five toes arched around the front of a large pad which has a long heel. It is usually 5 to 7 cm wide. In soft ground, claw marks and webs may be seen and print impressions can be deeper and look larger; the tail may also leave a mark. Male, female and cub prints might be distinguished by comparative size: adult male otter prints will be larger, and the prints of mother and cub(s), for example, might be found together. Sometimes not all five toes are visible and, depending on gait, prints can overlap, making tracks more difficult to separate from those of other mammals, particularly those of domestic dogs. Mink tracks are considerably smaller at only 2 to 4 cm wide, and the toes are more pointed than those of the otter; mink, stoat, and otter cub tracks may be very difficult to tell apart. Badger tracks are similar in size to otter tracks, but all five toes point forwards and are in front of the heel pad. Foxes and dogs have only four toes; domestic dog prints are most commonly misidentified as otter tracks, though the four toes of the dog print (compared to the otter’s five) are a ready diagnostic distinction.

Other signs – slides and castles

A site along a river bank used by otters to enter the water may be worn smooth to form a ‘slide’. On sandy substrates without prominent features, the otter may scrape up sand and stones into a small heap to spraint upon; this heap is sometimes called a ‘castle’. Where a bankside sprainting site is repeatedly used, the resulting increased fertility can lead to formation of a lushly growing and raised ‘spraint heap’ tussock protruding above the normal ground level. Some feeding signs are said to be typical of otter predation e.g. fish with the most energy-rich vital organs bitten away, with the rest of the carcass discarded otherwise intact on the river bank; it would be very difficult however to attribute this sort of finding conclusively to otters. The way otters handle frogs and toads is also said to be distinctive: the otter consumes the meaty parts but leaves the loose empty skins behind. Holts and couches comprise other field signs: please note it is illegal to disturb an otter’s breeding or resting place.

In some situations it may be possible to try to obtain tracks by creating a ‘sand trap’, an even covering of sand or other loose material over a solid surface such as a board left out overnight in the path that an otter might take. The technique would be viable only in certain circumstances, but has been used successfully at Devon Wildlife Trust’s Cricklepit Mill.

With rapid evolution of camera technology, relatively inexpensive motion-activated filming apparatus is becoming another useful method to survey for otters, in certain places.

For repeated surveys, such as regular monitoring of the same spraint sites, comparisons of activity over time are possible. Some further inferences about population size from quantity and freshness of spraint might be made, but the accuracy of this method is not universally accepted.

For monitoring otter presence, the standard survey protocols and a discussion of these are set out in Chanin, P. (2003) Monitoring of the Otter Lutra lutra. Conserving Natura 2000 Rivers Monitoring Series No.10 English Nature, Peterborough.

A survey might involve:

  • Checking 600m length of riverbank habitat for otter spraints and signs. For large scale surveys, 600m sections should be spaced at intervals of 5-8 km and there should be 80-100 survey sites covering the catchment. Likely sprainting sites, such as underneath bridges, within the 600m transect, can usefully be prioritised as the starting point.
  • Alternatively search for spraints in the immediate area (~50m) of the bridge / other monitored feature. This is sometimes referred to as a ‘spot check’ site survey.
  • Record the number of spraints and categorise each according to age: Not fully dry, Dried intact, Dried fragmented
  • Record any other otter signs (e.g. tracks)
  • Record relevant habitat features and draw a map (there is a standard form for this)
  • For repeat visits, record any changes to the habitat since the last visit
  • Carry out repeat visits. Some spot check surveys are repeated quarterly, others six-monthly

TIPS FROM THE EXPERTS

James Williams, Chairman of the Somerset Otter Group and author of The Otter (2010) and The Otter Among Us: An Understanding of the Otter in Britain (2000), offers the following advice for novice otter spotters.

  • Look early in the morning rather than late at night.
  • Give the otter some space. If you’re slap bang on the water’s edge you put stress on the otter. Try to get back a little, away from the river. At Beam Weir, for example, you look down onto the river from a railway viaduct; the otters probably know you’re there but you can’t harm them and they can go about their business without worrying about you.
  • Take up fishing. Otters don’t mind fishermen wading. When you’re fishing at night or standing in the river at dusk, quietly doing nothing, the otters know you’re there but they are in control of the situation. They can dive under and swim past you without you knowing they’ve swum past you. You can’t do much about them. But if you get out onto the bank to get your camera, they’ve lost control and will disappear. So fishermen wading sometimes see them, surprisingly.
  • Get downwind of the river. Don’t have your scent blowing across the otter.
  • Expect to be disappointed. If you find fresh spraints one morning and go back at night to look for the otter, it probably won’t be there. It could be five miles away. It will come back – within a fortnight. Paul Chanin, who wrote The Natural History of Otters, said that it’s easy to see an otter in Devon. If you sit on a bridge for a fortnight, you’re bound to see one for ten minutes. That’s as long as it takes the otter to go under a bridge, and every bridge in Devon has an otter under it about once a fortnight.

Tim Cox, Head Keeper at the Dartmoor Otter Sanctuary at Buckfastleigh suggests:

  • Leave your dog at home.
  • Don’t wear perfume – an otter’s keen nose will pick up any scent.
  • Stay downwind from the river – if an otter catches wind of you it will go in the other direction.
  • Waterfalls are good places to look because oxygenated waters attract fish which, in turn, attract otters.
  • Look for holts in upturned waterside trees. An otter may have up to five holts in a ten mile radius so keep walking and looking. You may find thin twigs outside a holt – they are an otter’s calling card.
  • Narrow tracks or chutes from the river to the bank are important escape routes for otters. You may see many such chutes along riverbanks frequented by otters.
  • Be patient. Otters appear in unexpected places. When you expect to see them you don’t, and when you’re not prepared, that’s when you’ll probably see one.

A close encounter

When asked about his best otter moment, James Williams, Chairman of the Somerset Otter Group, told this remarkable story:

“I was fishing in the Taw and an otter came down the far bank and swam across and started to work up the river. There were reeds on the left hand bank, and I had a rip in my waders so I couldn’t go out very deep, so I was standing close to the reeds, fishing, when I saw the otter. He was getting things out of the base of the reeds, pulling little fish out of the base of the roots as he came up, and as he passed me he kicked off against my leg. He didn’t know I was there. I think he thought I was a post or a rock or something, he carried on doing it. They’re all good otter moments, aren’t they?”

Verification of records

Records can be validated by DBRC through

  • Spraint
  • Photograph of tracks
  • Spraint or track record from a reliable recorder

Local and national studies

OPERATION OTTER Devon Wildlife Trust’s Operation Otter comprises regular surveys, monitoring and mapping the distribution of otters in the county’s streams and rivers with the help of trained volunteers. Each volunteer is allocated a stretch of river. He or she selects several sites within the allocated stretch where a passing otter would be likely to leave signs. The volunteer visits the river four times a year and records signs, spraints and tracks at each of the survey sites. The survey records are sent to the Devon Biodiversity Records Centre for inclusion in their database of species records. Information obtained from the surveys is used by the Devon Wildlife Trust to help target conservation efforts.

AXE OTTER SURVEY The River Axe flows through three counties: Somerset, Dorset, and Devon. Twice per year on the same weekends in April and October, members from all three county otter groups carry out spot check surveys of the same locations each year, covering the River Axe and tributaries such as the Coly, Yarty, and the Umborne. Presence / absence of spraints and signs, and number and freshness of spraints, are recorded. This regular snapshot survey gives an idea of current otter activity and comparisons between years. In Devon the contact for the Axe otter survey is Devon Biodiversity Records Centre.

HIGHWAYS AGENCY and ENVIRONMENT AGENCY post mortem studies

Otters killed by vehicles have been collected by The Environment Agency and sent to Vic Simpson, and independent veterinarian working in Cornwall, for post mortem. With the higher populations of otters in Devon and Cornwall, many of the samples obtained for this study came from Devon’s roads, including the main trunk roads A38 and A30. Many aspects of otter health were recorded. Findings are published in: Simpson VR (1997) Health status of otters (Lutra lutra) in south-west England based on postmortem findings Veterinary Record 141: 191-197

University of Exeter School of Biosciences

Otter Project—Population genetics and ecotoxicology

  • Population genetics. This project aims to improve established techniques for using DNA extracted from spraint to census otter populations. The technique will be used to count and determine the genetic diversity of otter populations using the River Camel catchment in Cornwall and the River Itchen catchment in Hampshire.
  • Ecotoxicology. In collaboration with Cardiff University Otter Project, this project studies levels of polybrominated diphenyl ethers PBDEs in otter livers.

CARDIFF UNIVERSITY OTTER PROJECT

The Environment Agency funds researchers to conduct post-mortem examinations of dead otters. Cardiff University Otter Project (CUOP) has examined over a thousand otters, mostly killed in road traffic accidents, following work pioneered in Cornwall by Vic Simpson. These otters’ deaths, while regrettable, provide the opportunity to take observations, measurements, biological specimens or samples that can be of great benefit to ecological research. In addition, the location of mortality incidents has been used to put in place mitigation on roads to reduce the number of future casualties.

CUOP also collaborates with other universities and organisations, including Swansea University, the Wildlife Veterinary Investigation Centre in Cornwall, University of Exeter, the Natural Environment Research Council’s Stable Isotope Facility at East Kilbride, and the National Museums of Scotland to carry out a wide range of research.

  • Landscape genetics. This study uses otter specific microsatellite primers to analyse muscle samples and aims to examine sub-structuring within otter populations, determine source populations involved in the re-colonisation of England, and assess the contribution made by reintroduced animals to population recovery.
  • Diet. Cardiff and Swansea universities are collaborating to examine otters’ diet, specifically prey remains in the stomach and gastrointestinal tract.
  • Ectoparasites. In searching for ectoparasites in otters, CUOP has identified several species of ticks. Future analysis should determine seasonal and spatial patterns of infestation.
  • Endoparasites. During examination of the digestive tract, endoparasites are removed for identification. In addition, animals are screened for Angiostrongylus vasorum (canine heart worm), a parasite capable of causing severe respiratory and heart problems to dogs and occasionally members of the mustelid family. A recent concern has been the finding of bile fluke infestation in otter populations
    • Pseudamphistomum truncatum: In light of the recent finding of the bile fluke P. truncatum in the gall bladders of otters and mink from Somerset, gall bladders are now also retained for further examination. Research is being undertaken to genotype the fluke and assess routes of spread, and to develop a DNA screening method that can be applied to spraint.
    • Toxoplasma gondi is a common parasite which causes the infection known as Toxoplasmosis. T. gondii is a major cause of death of the southern sea otter, but levels in Eurasian otters have not previously been assessed.
  • Lead levels. CUOP is collaborating with the Wildlife Veterinary Investigation Centre in Cornwall to examine lead levels in otter bone.
  • Cranial morphometrics. Examination of otter skulls to reveal sexual dimorphism in size and shape.
  • Age. During analysis of cranial morphometrics (above) the degree of closure of cranial sutures is examined in relation to other indicators of age. This will be useful in assessing population structures and bioaccumulation of chemical pollutants.
  • Polybrominated diphenyl ethers (PBDEs). CUOP is collaborating with the University of Exeter to analyse the presence of PBDEs in otter livers.
  • Polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCs). Analysis of PCB and OC levels in otter livers has been completed for all samples collected 1992-2003.
  • Marine derived nutrients (MDNs). A pilot study in collaboration with the NERC Life Sciences Mass Spectrometry Facility has generated promising results, and further analysis is underway to examine nutrient cycling within welsh catchments using otter muscle and bone.
  • Scent Analysis. This study aims to assess variation in the chemical profile of material from otter scent glands. Variations will be analysed to test for differences between individuals and between groups. It is hoped that this can be used as a monitoring tool to identify individuals from the scent signature in field collected spraint.

References

  • Allen, D. (2010) Otter Reaktion Books Ltd, London
  • Chanin, P. (2003) Monitoring of the Otter Lutra lutra Conserving Natura 2000 Rivers Monitoring Series No.10 English Nature Peteborough
  • Chanin, P. (2003) Ecology of the European Otter Conserving Natura 2000 Rivers Ecology Series No.10 English Nature Peteborough
  • Chanin, P. (1993) Otters Whittet Books Ltd, London
  • Chanin, P. (1985) The Natural History of Otters Croom Helm, London
  • Kruuk, H. (2006) Otters ecology behaviour and conservation Oxford University Press, Oxford
  • Kruuk, H. (1995) Wild otters predation and populations Oxford University Press, Oxford
  • Laidler, L. (1982) Otters in Britain David & Charles, Newton Abbot
  • Liles, G. (2003) Otter breeding sites Conservation and management. Conserving Natura 2000 Rivers Conservation Techniques Series No. 5 English Nature, Peterborough
  • Mason, C.F. & Macdonald, S.M. (1986) Otters: Ecology and Conservation Cambridge University Press, Cambridge
  • Ruiz-Olmo, J., Loy, A., Cianfrani, C., Yoxon, P., Yoxon, G., de Silva, P.K., Roos, A., Bisther, M., Hajkova, P. & Zemanova, B. (2008) Lutra lutra. In: IUCN 2010. IUCN Red List of Threatened Species. Version 2010.4. <www.iucnredlist.org>. Downloaded on 04 May 2011
  • Williams, J. (2010) The Otter Merlin Unwin Books, Ludlow
  • Williams, J. (2000) The Otter Among Us: An Understanding of the Otter in Britain Tiercel Publishing, Wheathampstead
  • Woodroffe, G. (2001) The Otter The Mammal Society, London
  • World Conservation Union, The (1992) Otters Switzerland
  • Williamson, H. ([1927], 1995) Tarka The Otter Puffin Classics, London

Links