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Britain once had an estimated 200,000 coypus roaming its wetlands, a population that had grown from animals imported for the fur trade decades earlier. In 1981, a carefully planned eradication campaign began, combining intensive trapping with population research, weather data and mathematical modelling to work out where and how hard the animals needed to be targeted. Officials kept checking for survivors, and in 1989 the government finally brought the campaign to an end. More than 50 farms were established, particularly in southern and eastern England, but keeping the animals contained proved difficult. The estimated number of adult females fell from roughly 3,000 when the campaign began in 1981 to about 20 by April 1986.
Because killing animals was not the same as stopping the population from recovering, the early control campaigns had difficulty keeping the population down. Because there was not enough biological information to plan them properly, gosling and Baker later described the earlier attempts as inadequate in part. An incentive bonus was therefore incorporated into the scheme to encourage them to finish the job rather than simply maintain a low population.
Escapes were common, and some of the animals released into the countryside found conditions in East Anglia particularly suitable. Large areas of reedswamp were lost during the 1950s, while some individual wetland species became extremely scarce.
Titled ‘ The eradication of muskrats and coypus from Britain ’, a population associated with farms near the Rivers Yare and Wensum became established around the late 1930s and spread into adjoining waterways, according to the study published in ResearchGate. The large South American rodents escaped from farms and found the waterways of East Anglia well suited to them, spreading through rivers, marshes and surrounding farmland. Then Britain changed tack. Within six years, the once-large population had been reduced to almost nothing. The campaign became one of Britain’s most ambitious efforts to eliminate an established invasive mammal. Its success depended on sustained monitoring and cooperation between scientists, trappers and government agencies, demonstrating how detailed population data could turn a difficult wildlife problem into a manageable conservation programme. Coypu were brought to Britain in the late 1920s to be farmed for their fur. Coypu were not merely living alongside Britain’s wetlands. They were feeding heavily on vegetation, including plants growing in the Norfolk Broads, and their feeding could destroy the plant rather than simply remove leaves. Sugar beet was among the crops they favoured, but cereals, brassicas and other root crops were also eaten. A particularly cold winter could cause a sharp decline, but numbers could rise again afterwards. The scientific work that eventually led to eradication was based on a much closer examination of population size, reproduction, trapping pressure and the effect of winter weather. The campaign also dealt with an unusual practical problem. If the trappers succeeded, they would eventually eliminate the population they depended on for work. The research programme also improved equipment and trapping methods, while field staff monitored progress and used capture rates to decide where effort was most needed. The change in numbers was substantial. The combination of sustained trapping and several cold winters accelerated the decline, although the researchers stressed that cold weather alone could not have removed coypu from Britain.
By the 1950s, they were damaging crops and eating away at wetland vegetation, while earlier attempts to control their numbers had failed to stop the population recovering.
