About Otters on the river worth

Picture courtesy of Rob Withey. Unfortunately not photographed on the Worth.

Everybody loves otters, except perhaps for anglers and pond owners! We have otters visiting the River Worth, here's a little information about otters in general and in more specifically about their life on the Worth.
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Back from extinction.
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​In the 1970’s the otter was close to extinction in England, only being found on 6% of surveyed sites. The steady decline earlier in the 20th century was largely due to water pollution with agricultural pesticides, other factors were illegal hunting and habitat loss.
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Following new regulations to control damaging pesticides, such as dieldrin and aldrin, instituted in the late 1970s, and the passing of the Wildlife and Countryside Act of 1981 which lead to habitat restoration, otter numbers have steady increased. This has been partly by natural territory spread but also due to managed re-introduction in areas such as east Anglia where they were previously completely absent. The increase has been remarkable, in 2018 otters were found at 96% of surveyed sites in England.
 

Otters on the Worth.
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​River Worth Friends are pleased to say that the Worth is no exception, otters or signs of their presence have been seen at a number of locations on the river.
Otter range over a wide territory, a female may cover 20-30 km or river, a male territory may include a number of female territories. So we suspect that the otters on the Worth are not actually resident but visitors from the Aire, we are hoping that an upcoming survey will be able to get more detail on this.
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Is it an otter or a mink?

It is easy to mistake a mink for an otter and vice verse. Here are a few features to distinguish them:

• ​Size. Otter are much bigger than mink, an adult otters body is about 95cm plus a tail of about 40cm, females are shorter. They weight between 7 to 17kg (15 to 37 lb), about the size of a medium sized terrier. While an adult mink is about 30-50 cm body length plus a tail about 20cm and weighs around 0.7-1.6 kg (1.5-3.5lb), about the size of a ferret, to which they are closely related. Otters have a much stouter tail which they use for swimming whilst mink tails are much thinner and less muscular.
• Colour. Mink are much darker, almost black, otters are a grey/brown colour.
• Swimming style. They have different swimming styles. Otters swim in a more submerged position with only their head and tail showing while the mink will have it's back showing. Also the heads are quite different, the otters being quite broad with a rounded face while the mink is weasel faced, narrow and pointed. Mink tend to be more terrestial than otters. The otter is more at home in the water than mink, it's body shape and webbed feet mean it's a more aquatic animal than the mink which is more often seen on the bank than in the water.​

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There are brief videos of a an otter and a mink on the Worth later in the blog. They show the different confirmation of the mink to the otter.
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Otter spotting.
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​English otters are elusive creatures! They are mainly crepuscular, emerging at dawn and dusk, so they are usually out in the dark. The best way to find out if otters are present is to look for their spraints, posh name for droppings, or for their prints. You could also try filming with a trail camera.
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Otter spraint found on river in Keighley. Dried out a bit so light coloured

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Otter spraints.

​Otters use their spraint to mark territory so it is often left on the top of large stones where it is evident. Often one stone will have a number of spraints. The spraints are cylindrical, about 2cm wide, a bit squishy and dark green in colour, getting lighter as it dries out. It will obviously contain bits of what it last ate, ie fish scales and bones, bits of insect and sometimes aquatic bird. On the Worth they will most likely have bits of crayfish (eating crayfish may also colour the spraint orange). Otter spraints can be confused with mink, however mink droppings are usually smaller but the best way to tell the difference is to have a good sniff! 

​Otter spraint usually has a sweet, fishy, some even say jasmine tea-like scent, while mink scats smell like shit, or some say burnt rubber .

​RWF members have spotted otter spraints by the river at Pitt St. and under the bridge at Dalton Lane, both close to the centre of Keighley, we didn’t need to sniff them.
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Otter tracks.
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​These may be found in wet sand or mud along the river bank. Otter prints usually show five toes whilst a dogs has four. They can be confused with other mustelids such as weasel, mink and stoat but otters are much bigger, 9cm compared with 1-4cm We have seen otter tracks by the river near Pitt St.

Otter foot prints.

Trail camera.

If you really want to get into otter spotting you could set up a trail camera along the riverside. You obviously need to find a secluded location and camouflage the camera well, we understand there might be some dishonest people in Keighley who may steal it. Try to find somewhere with a gentle sloping bank, possibly under a bridge. We have filmed an otter in the river near Pitt Street.

​Clearly Pitt Street is a favourite otter hangout.

Help River Worth Friends. If you have any luck otter spotting we would love to hear from you. Any information will help us build up a picture of otters on the Worth. Report any signs or sightings via our contact page,
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Brief shot of otter filmed on trail camera at Pitt Street.

Brief video of mink filmed on the same day and location as the otter

Otter facts.
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​The otter family:       Otters are part of the mustelid family, so related to weasels, stoats, mink and badgers

 Size:                           A full grown male otter can be up to 95cm plus a tail of about 40cm females are                                                     shorter.  They weight between 7 to 17kg (15 to 37 lb).

Lifespan:                      ​Up to ten years though many die well before that. Nowadays the main cause of death                                           is road accidents.

Diet:                              ​Mainly fish such as trout, grayling, eels and carp (on the Worth it would be trout and                                            grayling) but also amphibians, crustaceans (lots of crayfish on the Worth), and                                                       waterbirds like moorhens and ducks. They also hunt on land, occasionally consuming                                          small mammals, birds, and insects. 

       
Offspring:                    Young otters, known as pups or cubs, are born from May to August, they are blind,                                               weighing about 100g (3.5oz). Female otters can delay implant of the embryo meaning                                          they can mate at any time but delay implantation to give birth when conditions are                                               right.

A pair of young otters, not on the Worth, these photgraphs were taken at the Strid on the Wharfe by RWF member Malcolm Eldon.