In 1981, Britain wanted to eradicate the invasive coypus which escaped from fur farms and grew to roughly 200,000 in population and damaged crops and wetlands; after years of trapping Britain made them disappear from the country

Britain once had an estimated 200,000 coypus living across its wetlands and waterways. The large rodents had not always been part of the country's wildlife. People brought them to Britain for fur farming, but some escaped and established themselves in the wild.

By the 1950s, the animals had become a serious problem in parts of East Anglia. They fed on crops and wetland vegetation and became difficult to control. Earlier attempts to reduce their numbers had failed, with the population recovering after large-scale killing campaigns.

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In 1981, Britain took a more scientific approach. Instead of simply trying to kill as many coypus as possible, officials used research, trapping data, weather records and mathematical models to work out how to eliminate the population. After six years of intensive trapping, the invasive rodents had almost disappeared from the country.

How coypus came to Britain

Britain introduced coypus in the late 1920s for the fur trade. More than 50 farms were established, particularly in southern and eastern England.

The animals were difficult to contain. Escapes from farms helped establish wild populations, particularly around the Rivers Yare and Wensum in East Anglia.

The coypus found the region's waterways and wetlands suitable for survival. Their numbers gradually increased, and by the following decades they had spread through parts of the countryside.

The population eventually reached an estimated 200,000, although researchers later noted that this figure may have been an overestimate.

Why Britain wanted them gone

Coypus were not simply an unusual addition to Britain's wildlife. Their feeding habits caused problems for both farmers and wetlands.

The rodents ate sugar beet, cereals, brassicas and root crops. They also fed heavily on wetland vegetation, including plants growing in the Norfolk Broads.

Their feeding could destroy plants rather than simply removing parts of them. Large areas of reedswamp disappeared during the 1950s, while some wetland species became increasingly scarce.

Britain had already tried to control the animals. During 1961 and 1962, around 100,000 coypus were killed, but the population recovered.

The problem was that killing large numbers was not enough to guarantee eradication.

Britain changed its strategy in 1981

Britain launched its decisive eradication campaign in April 1981 with 24 trappers.

This time, scientists helped determine where the animals were concentrated and how much trapping would be needed to drive the population down. Researchers also studied reproduction, capture rates and the effect of winter weather on coypu numbers.

The campaign continued year after year. Between 1981 and 1986, trappers carried out hundreds of thousands of trap-nights annually.

Officials also faced an unusual problem. If the campaign succeeded, there would eventually be no coypus left for the trappers to catch. The programme therefore included an incentive bonus designed to encourage the trappers to complete the eradication rather than simply keep the population low.

Coypu numbers collapsed

The campaign produced a dramatic decline.

When the programme began in 1981, researchers estimated that around 3,000 adult female coypus remained. By April 1986, that figure had fallen to about 20.

Several cold winters helped accelerate the decline, but researchers found that weather alone could not explain the disappearance. Sustained trapping played the central role.

By 1987, officials believed that no breeding population remained.

Britain did not immediately declare victory. Authorities continued checking for surviving animals because even a small number of coypus could potentially restart the population.

In January 1989, the government finally announced that the trapping programme had succeeded and was being wound up.

More than 10,000 coypus had been eradicated during the campaign. Officials still warned that isolated animals could survive and asked people to report sightings.

How Britain almost wiped out an invasive species

The coypu campaign became an example of how a country can tackle an invasive species through sustained, targeted action rather than repeated attempts at mass removal.

The earlier campaigns had killed large numbers but failed to eliminate the population. The 1981 programme combined trapping with biological research and population modelling, allowing officials to concentrate efforts where they were most effective.

The approach also showed why eradication can become harder as an invasive population recovers. Britain had to maintain pressure for years until the number of breeding animals became too small for the population to sustain itself.

By the end of the campaign, the coypu that had once numbered in the hundreds of thousands had been reduced to almost nothing.

What began with animals brought to Britain for their fur had eventually turned into a major wildlife and agricultural problem. Decades later, intensive trapping finally brought the country's wild coypu population to an end.