Otter Lutra lutra

The otter is an European protected species, protected under Schedule 5 Sections 9(1) and 9(4) of the Wildlife & Countryside Act 1981 and the Conservation (Natural habitats &c.) Regulations 1994. The latter regulations (usually referred to as the Habitat Regulations 1994) implement the European Habitats Directive in the UK.

Under the legislation it is an offence to: deliberately kill, injure or take an otter from the wild without a licence; deliberately disturb an otter in its resting place or damage or destroy an otter’s breeding or resting site.

A licence issued by Natural England is required to carry out certain activities that could adversely affect otters if these activities fall within 50 metres of an otter’s holt or resting up site.

Otters will mainly feed on fish (40-90% of their diet)and will take a variety of species depending on the time of year, species such as carp, stickleback and eels. During the spring months amphibians form a large part of their diet. Occasionally otters will take small mammals and water birds such as coots. Manmade,domestic materials have also been found inside otters.

Generally they are opportunistic and catch their food whilst travelling throughout their range; their ranges are surprisingly large and in adult males these are likely to be in tens of kilometres.

Since the start of the reintroductions of otters in 1983, they have spread well and now have a presence on most of the rivers in Norfolk as well as on parts of the coast. It isn’t always the main channels of the rivers they use, they will also take advantage of the streams, ditches, fens and reed beds.

Otters mainly sleep and rest during daylight hours in dense cover or in cavities in trees and below ground – the latter are known as holts and these are also used for breeding. Within its range, an otter will use a number of resting and holt sites.

It is important to remember that otters are protected by law as well as their habitats and it is an offence to disturb and otter or its habitat.

The most distinctive and easiest way to find otter signs are their droppings which are called spraints. Distinguishing between mink and otter droppings is relatively easy with mink scats being long and twisted in shape with a very unpleasant smell when fresh.

Otter spraints are left in prominent places such as on ledges under bridges and on rocks. They vary in shape, colour and consistency but always have a very distinctive musky, fishy smell, reminiscent of jasmine tea or newly mown hay.

The spraints have a unique, signature scent that is unique to each individual otter and this is the way of conveying information to one another.

Another way of revealing if otters are on site is looking out for their footprints. The footprints of otters are asymmetric and normally only show four toes even though they have five, although this depends on the surface they have been walking over. The webbing between the toes doesn’t normally show. Print sizes range between 40-80mm across. The prints of mink are much smaller across and the toes more spread out.

Both species are agile swimmers and catch fish by chasing them underwater. The otter needs to eat 20 per cent of its body weight in food every day - about 2.5kg and will be able to tackle larger prey items than mink. Otters will usually eat the fishes head first and will quite often leave the tail. The mink has a wider diet but will take smaller fish. A feeding station will contain lots of fish scales and fins especially in the winter months.

To ascertain which species is involved you should firstly look for any footprints the animal may have left in the mud around the feeding area:

Otters are much bigger than mink and have 5 toes on each foot connected by webbing (although this is not always obvious and the print marks left usually only show four toes). The overall footprint shape resembles that of a kite with a footprint approx 7cm long and 6cm across. The hind print is generally bigger and can be up to 9cm in length. The claw marks are represented as slight indentations.

Mink also have 5 toes on each foot but the prints are much smaller with fore prints approx 3.5cm long and up to 4cm wide. The hind print is up to 4.5cm long. The prints are roughly oval in shape with clearly defined claw marks

Your next piece of detective work would be to see if the animal may have left some droppings nearby:

Otter droppings (called Spraints) are black and slimy when first deposited and have a strong oily smell. Over time however they become light grey and lose their thick consistency. The droppings are made up almost exclusively of fish bones, scales and the hard shell fragments of crustaceans. Otters use droppings as scent markings and they are quite often left in exposed places (raised banks or vegetation, stones etc).

Mink droppings are generally 6-8cm long and approx 6-9mm wide. They are often twisted and pointed at one end. Close examination is likely to show a much wider range of prey remains including the fur and bone fragments of small rodents, bird feathers and also the husks and pips of fruit and berries. If the mink has been eating fish the droppings are likely to resemble thin otter spraint but with a faintly acrid smell. The droppings are often used as scent markings, although some will be inconspicuously placed.

The otter is a protected species and it is illegal to trap or harm it in anyway. The mink however is a relatively recent introduction to Great Britain, and represents a threat to some native animals, in particular the water vole. Mink are categorised as a pest species and are widely trapped.

The non-native American mink is in the same mammal family as the otter, stoat and weasel, and resembles all of these species in general body shape. It is quite commonly confused with the otter, especially in wetland habitats, but there are several important differences. It has a long, slim body, short legs and a round, fluffy tail that is about a third of its body length. The otter’s tail is broad-based, flat and tapers towards the tip and is about half the body length. In size American mink are larger than stoats and weasels but smaller than a domestic cat and about half the size of an otter. The average body length is 60cm for males and 50cm for females. The tail adds an extra 14 – 21cm. The fur is rich, glossy and generally dark brown or black, with a white or pale patch on the chin only. The pale markings on an otter extend from the chin to the chest. The muzzle of a mink is pointed and ferret-like whereas the otter has a flattened head shape and a broad dog-like muzzle. The mink swims high in the water with the head and body visible but the otter swims low in the water with only the head and part of the tail on show.

It is not possible to trap and/or move otters anywhere within the UK. Otters are protected under the UK Wildlife & Countryside Act and also under European legislation.

Otters are mainly a river dwelling species and it is in their nature to eat fish, eels and crustaceans. About 40-80% of an Otters diet consists of fish with them eating around 1kg a day. An enclosed fishery or pond simply offers a very tempting feeding opportunity for them.

It should be remembered that most still waters stocked with fish are artificial, manipulated environments that support high densities of small fish or small concentrations of very large fish (usually carp) which, from the perspective of the otter, constitute part of its range and provide foraging opportunities. The onus for protecting a fishery against predation falls with the owner, or the club/syndicate using the fishery and in relation to otters this can only effectively be achieved by fencing of a specific design.  Fisheries that are used by the public may be eligible for a grant from the Environment Agency but otherwise the cost is the responsibility of the fishery owner, club or syndicate.

Information on appropriate/effective fencing specifications is available from a number of sources including the Angling Trust, Specialist Anglers Conservation Group, the Environment Agency and Norfolk Wildlife Trust

For smaller garden ponds it may be possible to cover the pond in a mesh or grid to stop the Otter being able to dive down to the fish.

Otter populations crashed to near extinction across most of lowland England by the mid 1970’s as a result of pesticide poisoning, loss of habitat and hunting. Otters were released by the Otter Trust in Norfolk between 1984 and 1997 with the approval of the statutory conservation bodies existing at the time; there have been no releases since then (other than orphaned otters which are released by the RSPCA as close as possible to the location that they came from).  It is worth pointing out that since the 1970s, otters have also spread naturally from western lowland England back across the Midlands into eastern England, so the release programme simply speeded up their natural re-colonisation of Norfolk.