The Cheshire Dormouse Re-introduction
As part of an English Nature program to restore the dormouse to a part of its former range they have been re-introduced to woods in several counties where they had become extinct. Cheshire Wildlife Trust was delighted to be a partner in the return of the dormouse to Cheshire. In 1996, 29 captive-bred dormice were released, followed by 24 more in 1997. Using captive bred animals minimises the number of dormice which have to be removed from existing wild populations.
The dormice were placed in specially designed release cages and left to settle in. After a few days the cages were opened so the dormice could come out and explore. During this time food was supplied in the release cages and this was continued for several weeks. This provision of food is very important as it takes the dormice some time to explore their new home and discover the natural food sources; they need a reliable food supply during this time.
At the same time as the release, CWT put up a large number of specially designed dormouse nest-boxes around the release site. Dormice spend the day in snug nests which they weave out of strips of bark, dry grass and leaves. They build these nests in tree holes or in dense vegetation, but they will readily use purpose built nest-boxes. They seem to like our nest-boxes and females will happily use them to raise families in.
As well as providing secure nest sites, the boxes make it much easier for us to find the dormice. Dormouse nests are normally very well hidden and the animal itself is nocturnal and very hard to spot, so without the nest-boxes it would be almost impossible to find out how well our dormice are doing.
Releasing animals into the wild is never guaranteed to succeed, so it is important that the dormice are monitored, so that we know whether the population is thriving. Monitoring is carried out 4 times during the summer and early autumn (i.e. whenever the dormice are active). Each time all the nest-boxes are checked and any dormice found are weighed and sexed, and then returned to their nests. They seem to cope very well with this disturbance and sometimes we find the same dormouse in the same nest in several consecutive months. Weighing the dormice gives a good indication of their state of health.
So far, the results have been very encouraging. In 1996, the newly released dormice bred for the first time in their new home. In 1997, there were several more litters of babies, including one litter born to a female who was herself born in the wood the year before. Successful breeding is important, as unless the dormice can reproduce themselves the population will quickly disappear. Since then the dormice have continued to do well, with new litters of young being born every year. They did particularly well in 1999, when the weather was very favourable for them and the population almost doubled. In 2000 we found one female who had reached 3 years old; this was quite a landmark as she was the oldest animal known in the population. In the wild dormice can live for 5 years or more, although most will not reach this age. This particular female turned up frequently during monitoring. She remained in a fairly small area and has raised four litters of young over the 3 year period.
The area of woodland occupied by the dormice has increased slowly with time. When young dormice leave their mothers, they spend some time travelling and exploring before they settle down; this is when new areas of woodland are colonised. We have put nest-boxes in the areas we think are most likely to be colonised in the near future in order that we can determine how far they have spread and are spreading. By 2001 the dormice had colonised a patch of woodland about 500 meters from the main release site.
2002 was a very good year for dormice. The hazel produced a bumper crop of nuts, and trees such as hawthorn and crab apple also fruited well. This meant there was an enormous amount of food for dormice. They responded by having larger families than usual. In the autumn monitoring we found several females with 6 babies and one with 7 – they usually have only 4 or 5.
We are eager to see how our dormice progress in future years.
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