Like many of our mammals the Edible Dormouse is a non-native species. It colonised an area of the Chilterns around Tring in Hertfordshire having escaped from the collection of Lionel Rothschild in 1902. Since then the species has failed to spread any considerable distance and populations in Hampshire and Essex are the result of deliberate releases.
Edible Dormouse, Tring
In the Chilterns the population has been monitored for some 20 years or so and the survey work is currently headed by Roger Trout. On 20/09 I travelled to Tring with members of the Warwickshire Mammal Group to give Roger a hand with checking the nest boxes. This is done twice a month between April and October and is a considerable task as over 700 animals can be found during a single round of checks. The size of the Chilterns population varies and 2015 has been a poor year. At the survey site the Dormice have not bred due to a shortage of food caused by a failure of the Beech mast crop. There are few Oaks here so acorns, the other principal food source, are not available in sufficient number.
They hibernate underground and only use the nest boxes as summer nesting sites. We caught around 20 animals and it appears many of them have gone in to hibernation early. The nest boxes are of an excellent design but have to be opened in to a large bag or the super agile occupants will easily evade capture. An awful lot of hard work can now be avoided by checking inside the box with an endoscope to see if it is (or may be) occupied.
Ben Wood of Warwickshire Mammal Group checking an Edible Dormouse nest box at Tring
If occupied the hole is bunged, the box taken down, the animal removed and the weight, sex and location are recorded along with the presence or absence of young and reproductive condition of females. Dormice and nest material are then returned to the box which is replaced on its tree.
Edible Dormouse being removed from a bag for processing
This was the first time I have seen the species and I have a feeling it will not be the last but I have to confess I am glad I got my first experience on a day when there were not 2-3 (sometimes as many as six) animals in virtually every box.