Coypu and muskrat-introduced and exterminated

 

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Ondatra zibethica = Muskrat

The Muskrat...

	weighs between 1 and 2kg
	is a seasonal breeder
	has a 22 day gestation period
	has a 30 day lactation period
	young are born naked
	builds nests/lodges out in the water where the young are protected from many predators

Ref : Gosling and Baker, 1989, Biol. J;38:39-59

The Muskrat was introduced from North America to Austria and Hungary in 1905. 5 pairs were released.

By 1926 there was 100 million muskrat which had also spread to neighbouring countries.

Muskrat cause great agricultural damage and dig up river banks.

MAC Hinton argued for the Destruction of Imported Animals Act of 1932 and a licence was required to import and keep Muskrat.

By 1932, the Muskrat had established itself near Shrewsbury and a total of 700 square miles was infested. 935 were trapped by October of that year.

Trapping...

In 1933 there was considerable concern that attempts to control Muskrat were not working.

By 1934, it was clear that the authorities were getting on top of things.

By February 1934, a team of 15 professional trappers had managed to reduce the number of Muskrat.

They used leg-hold traps fixed onto river banks which, once a trap had caught a Muskrat, would cause the animal to fall into the water and drown.

In Scotland 6500 non-target species were killed to remove just 1000 Muskrat (mostly Moorhens and Water Voles).

Muskrat burrow through banks and interfere with drainage. There was great relief when they were removed within 3 years.

Myocastor coypus = Coypu

The Coypu...

	much more susceptible to cold than the Muskrat, and also has a lower reproduction rate
	introduced to fur farms from South America in 1930s, there were early escapes, mainly in south-east England
	one place where the Coypu established was East Anglia, but a severe winter in 1946/47 killed off a lot of them
	by the 1950s there were concerns as they were established in the Norfolk Broads as well as East Anglia, and by the mid 1950s they were spreading out of the Broads expanding their distribution
	Coypu dig large holes in banks and dykes and also damage root crops
	in 1964, the Ministry of Agriculture, Fisheries and Food (MAFF) started a campaign to limit Coypu to the Norfolk Broads in the 'heartland' of their habitat-restricted range
	in 1963 however, there was the worst winter Britain had seen, and the Norfolk Broads were completely frozen over - the Coypu didn't do well as over 90% died
	by the end of 1965 the campaign was deemed a success as over 40,000 Coypu were caught
	cage traps were used and when a Coypu was caught it was shot, any other animal was released
	however after a run of mild winters in the  early 1970s, the Coypu started spreading again

The MAFF decided to eradicate the Coypu...

They calculated that 24 professional trappers would keep the population down, and 34 trappers would remove the coypu in 6 years. Salaries for the trappers were set at 3 times their usual salary if the Coypu was eradicated in 6 years, declining if the eradication took any longer than this. The eradication campaign began in 1981 with 48 traps/day/trapper set. Initially the ratio of caught females to caught males was 0.92, which then decreased to 0.163. This was because males are more likely to encounter a trap as they wander around much more than females. The last Coypu was caught in 1986 and a total of 35,000 Coypu were caught.

The Coypu and Muskrat were successful eradications because action was taken early in comparison to the case with the Mink. Political will (=finance), scientific expertise, the promise of success, and adequate trapping effort maintained well past the last trap successes, were a part of this.