Trapped muskrats

Muskrat numbers have increased greatly since the 1960s, but in the last 10 years they have been falling as a result of trapping and killing.

Trends

After the first muskrat was captured in the Netherlands in 1941 (in Valkenswaard), muskrat numbers rose sharply, peaking in 1991, when over 400 000 animals were exterminated (see graph). Since then, not only the number of animals trapped but also the number of animals trapped per field hour has fallen: in 1991 1.12 animals were trapped per field hour, but in 2000 the number was 0.63 per field hour. In 2001 both the number of animals trapped and the number trapped per field hour were higher than in 2000, suggesting that the muskrat population is increasing again. One reason for the recovery is that in 2001 the extermination campaign was hampered by the foot and mouth crisis.

The muskrat, which originates from North America, was imported into Europe for fur farms. Escapees have allowed the species to spread throughout Europe. Muskrats burrow into banks, and the resulting damage to the dikes and bunds in the Netherlands is very expensive to repair. For this reason the animal is treated as a pest. It has been suggested that the increase in nature areas and the creation of more natural banks benefits the species.

Technical note

The campaign to exterminate the muskrat involves hundreds of rat catchers every year. The graph shows the number of animals trapped and killed per year. This number depends not only on the population size, but also on the effort made to control the animals, which is why it is important to look at the number of animals trapped per field hour.

As a result of an improvement in the recording of kills in 1987, the figures after this date are not exactly comparable with those from preceding years.

References

• Landelijke Coördinatie Commissie Muskusrattenbestrijding (2002). Landelijk Jaarverslag 2001 Muskusrattenbestrijding. LCCM. Den Bosch.