When the coypu was Public Enemy No. 1 in Norfolk

Feeding the coypu at the East Carleton fur farm in this EDP cutting from October 1938. The previous year some of the 300 animals had escaped, and soon began to spread into the region's waterways. (Image: Archant)

It all began with a dodgy fence, and a would-be fur magnate with a name straight out of P G Wodehouse.

But there was nothing comical about the aftermath of the accidental release of a group of animals from farmland at East Carleton in 1937. For the descendants of those creatures – and other 'escapees' – would go on to cost us millions and take more than half a century to eradicate.

They were known at first as South American swamp beavers. But soon everyone was calling them by their more familiar name: coypu.

Their story is a fascinating one which encompasses sometimes bitter rows between farmers and conservationists, landowners and politicians, a generous helping of cutting-edge science – and, at times, more than a hint of Ealing-style farce too.

Ted Ellis - Naturalist at the forefront of the debate. (Image: Submitted)

Looking back on my memories of the 1960s and 1970s, it seemed to me that almost every edition of About Anglia or Look East had a coypu story on it. Of course, it could not really have been that way - but what was certain was this was definitely a story which ran and ran and ran...

The roots of the tale go back more than 80 years to 1929, when would-be enterpreneurs in this country began to import a species of large rodent from Argentina. The adult swamp beaver is around two feet (60mm) long – not counting the rather rat-like tail – and weighs around 20lb (9kg).

With its combination of walrus whiskers, stumpy body, webbed hind feet and large orange front teeth it was never going to feature on the list of the most elegant animals in nature.

In fact, with a bit of poetic licence, it could be presented as something rather fearsome, which explains why it was exhibited at the Great Yarmouth Easter Fair in 1935 as the 'giant sewer rat', accompanied by a rather lurid painting of two sewer workers fending it off with shovels.

Spread of coypus in Norfolk. (Image: Archant)

The farmers weren't, of course, interested in its looks: it was its fur which was the big attraction. Its belly yielded a fine, soft undercoat of fur known as 'nutria', with 22 of the animals producing enough pelts to make one fur coat.

And among those hoping to make a lucrative sideline was the delightfully-named landowner Philip Tindal-Carill-Worsley, who had bought the East Carleton Manor estate in 1924. He set up a coypu farm on his 120-acre land – he also had silver foxes for the same reason – and was one of three Norfolk landowners to dabble in the nutria trade.

But then in 1937 heavy rain caused a few sheets of galvanised iron to collapse, and some of the coypu immediately seized their chance to escape and head for the nearest watercourse. All of the country's nutria farms had closed by 1940, but the consequences lingered on for decades. A year after their escape coypu were noticed near Cringleford; within a few years they had reach Oulton Broad and the lower Yare and Waveney.

At first, they were rarely spotted at all. Naturally very timid, they tended to vanish at the first sign of danger. Their presence was only betrayed by tell-tale fast moving bubbles, and that distinctive whiskery snout.

With a war on, people had much more on their plates to deal with that this additional to the local fauna, although the animals' 'voracious vegetarianism' was being noted by 1943. The following year came the first complaints about them: that they were damaging reed beds.

For their numbers were increasing – fast. Like herbivores the world over, their principal survival mechanism is to out-breed their predators. Maturing after eight months, coypu can breed five times in two years, with up to nine young in each litter.

This, of course, had made them very popular with the fur farmers, as one pair of coypu could produce 60 descendants over their three-year lifetime. All very lucrative, at least in theory. But once they were out in open country, that fecundity was another matter entirely.

Soon people were harking back to the case of the musk rat. Introduced into Europe in the first years of the 20th century for its fur, it too had (inevitably) escaped. Five animals which wriggled out of an estate near Prague in 1905 had become – according to one fanciful and suspiciously exact estimate – 100,000,000 by 1932. In this country the musk rats were eliminated by 1928 only after a long and expensive eradication campaign.

And yet here we were, just one year later, importing another voracious non-native herbivore. Would we ever learn? You have to say: apparently not.

In mainland Europe the musk rat was blamed for burrowing into, and weakening, river banks – the reason why they are still tightly controlled in the Netherlands to this day – and this charge was soon being levelled at the coypu. This claim would be made again and again over the years but of this, at least, the coypu may have been unfairly pilloried.

By 1945 Mr H W Palmer, Pests Officer to Norfolk War Agricultural Executive Committee, was saying: 'We have trapped and killed hundreds, especially in the Cringleford and Broads areas. They have become a feature of our fauna.'

He also went on to say that in his opinion they were 'harmless and purely vegetarian, living largely on the shoots of young rushes, and I do not think they do much real damage.' He said there was 'no evidence' that they damaged river banks. It was clear that it was its large increase in numbers that some people found unsettling.

The bitter winter of 1947 did for many of the coypu, and population crashes were to be a feature of every sharp winter from then on. In wintertime, too, they were easy to spot, and therefore easy to kill, as they tended to huddle together for warmth. But as soon as spring came, numbers rapidly grew once more.

Not everyone bought into the 'giant rat' image. In fact they were so popular in the 1940s with children in Cringleford – one of their early strongholds – that they would deliberately spring the traps to free them.

While the population spread (by 1948 they had reached the mouths of the Nar at King's Lynn and the Yare at Gorleston) there was still much debate about their impact.

Ted Ellis, that doyen of Norfolk naturalists, would be closely involved over the years. At this time, he was pointing out that the coypus were mainly eating reeds, and said they only 'very occasionally' damaged sugar beet crops. 'I have watched coypus at close range often enough and found it hard to wish them ill,' he said. But at the same time he recognised that they were affecting rare plants on Surlingham Broad, and reluctantly concluded that 'their increase must be checked by man'.

Later than year the Great Ouse Catchment Board reportedly made – and quickly withdrew – a £5 reward offer for each coypu skin handed in. Someone, it seems, had had a gentle word in the ear of officials and pointed out that if they offered that much (worth £160 in today's money) then very soon the fly ol' country boys would be busy catching coypus, all right. For breeding.

The trouble was no-one could really agree how damaging the coypu were. The GOCB's official position was that it was a 'potential menace' on its artificially banked waterways, but the East Norfolk Rivers Catchment Board chief engineer said he had not seen a single case of coypu damage in ten years.

Anthony Buxton of Horsey Hall wrote to EDP about his fears of tunnelling, fearing a 'major disaster'. 'I loathe these South American rats...' he said. But fellow landowner Henry Cator, of Woodbastwick, countered that the coypu were keeping the Broads waterways open 'free, gratis and for nothing...' by clearing out the bullrushes.

It didn't help the debate that there were just so many myths and half-truths floating around. The coypus' habit of growling when cornered (plus those orange incisors) led to some people fearing they would soon 'attack' Broads boating parties. J M Last of Corpusty had to write in in 1960 - you can almost hear him sighing as he put pen to paper – to point out that 'coypus do not lurk in banks and hedges to leap upon passing cyclists.'

But the knack of the animals in suddenly appearing in unexpected places such as suburban gardens, beaches and even Great Yarmouth Fire Station did not exactly endear them to local people.

In one startling 1961 incident a coypu even turned up in an outside loo at Litcham.

'What puzzles us,' wondered Mrs L G Hudson, of Front Street, 'is how it got there in the first place and managed to lock itself in.'

Well, you would, wouldn't you?

• Coming next week: A war declared - and won. But what if it happened today?