50 surveyors, 300 sites - but how many otters are in Cambridgeshire?

A snub broad nose breaks the water’s surface, darting dark eyes scan the riverbank, in a flash a sleek sinuous furry body slinks effortlessly onto the bank, water droplets falling from the thick fur.

Watching otters in real life - or on webcams, the option for most of us to see these elusive mammals - is always a captivating joy.

Playful by nature, quick and deft in movement there's a compelling, mercurial quality that captures the imagination and makes you smile at the sight.

Otters can now be found in almost every county in the country - along rivers, streams, in fens and reedbeds - anywhere watery with good ground cover to keep hidden.

Back in the 1950s otter populations were in steep decline and by the 1970s many waterways had no otter life. While population numbers have risen since then the otter still faces new and varied threats from habitat destruction (road building, new developments), persecution by fishery owners and gamekeepers (perceived as threats to fish and game birds), to the use of pesticides in farming - pesticides and pollutants can affect their reproductive system.

An otter survey is currently taking place across Cambridgeshire - as you read this, up to 50 surveyors, clipboards and cameras in hand, will be foraging under bridges, along riverbanks and streams in a total of 300 sites looking for clues and signs along the way.

Taking place every five years, the survey has been running for 30 years, starting in 1992, this year's being the seventh survey conducted in the county.

So where to find an otter and what are the clues to look for? One of the first places to look is under bridges – canny otters communicate and convey messages in their droppings, known as spraint.

They have worked out that this lasts longer under cover, so bridges provide a good place for this calling card. With a distinctive smell (apparently similar to jasmine tea) every spraint tells a story with a specific signature scent unique to each individual which contains and conveys information - whether male or female, if in season, etc.

Prominent places generally are ideal places for spraint: on ledges or rocks, and sometimes they will scrape up earth to create their own platform.

Another clue is tracks - otter footprints are asymmetric, ranging in size between 40-80mm and normally showing only four toes even though they have five, and the webbing between the toes also doesn’t usually show. Those lucky enough to see them may also hear the distinctive series of squeaks and whistles they make, though these are more normally heard at night.

Otters nest in riverbanks holes called holts, which will have a few different entrances to protect against flooding, with at least one entrance being above water level.

They may have several for different purposes - natal holts, where a female otter gives birth and raises her pups for the first three months, and nursery holts for raising older pups.

Females will raise two to three pups per season who will each stay with and remain dependent on their parents for over a year, leaving at 14 to 15 months old, and starting to breed at between 17 and 20 months old - breeding chances are slim in a lifetime as wild otters only live to around four years old. They feed on fish eating a variety of species depending on the time of year - carp, stickleback, eels, and during spring amphibians form a large part of their diet.

Have fired the imagination of Henry Williamson in the 1920s Tarka the Otter, and of Gavin Maxwell in the 1960s Ring of Bright Water, more recently Robert Macfarlane's Spell Song (illustrated by artist Jackie Morris) catches their magical fluidity:

“Otter enters water without falter -

what a supple slider out of holt and into water

This shape-shifter’s a sheer breath-taker, a sure heart-stopper,

but you’ll only ever spot a shadow-flutter, bubble-skein, and never (almost never) actual otter.”

The 2022 survey, conducted by staff and volunteers of the Wildlife Trust, along with members of the Cambridgeshire Mammal Group, will be completed at the end of February, with results towards the end of March.

Another element of this year‘s survey is the DNA testing of otter spraint by the Wellcome Trust; samples are being collected and frozen to then be analysed – watch this space . . .

Find out more at https://www.wildlifebcn.org/sites/default/files/2018-05/otter_survey_report_2017.pdf.

Read more from Caroline Fitton and the Wildlife Trust

Removal of the old guard at Trumpington Meadows

Giving peat a chance: The Wildlife Trust’s paludiculture project at Great Fen

The Wildlife Trust in Cambridgeshire introduces a Young People’s Forum