Endangered dormouse thriving in Yorkshire Dales wood

Dormouse in a state of torpor, photographed in Freeholders' Wood in October 2016. Photo: Ian Court, Yorkshire Dales National Park Authority.  

The population of one of Britain’s most endangered mammals, the dormouse, has been found to be stable in the Yorkshire Dales National Park.

The monitoring report for 2016, just published, suggests that numbers are up on the previous year.

Dormice were reintroduced into the 12-acre Freeholders’ Wood in Aysgarth in 2008.

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Licensed fieldworkers check each of the 255 nest boxes in the wood once a month from May to October.

Despite unsettled weather conditions last summer, there were no prolonged periods of rain, resulting in a reasonable breeding season.

Three litters were located in June, two in July, three in August, two in September and three in October.

There was a major surprise in May, when a box was found to be occupied by a dormouse as well as a pair of blue tits looking after a clutch of seven eggs.

On a subsequent visit, the box was found to be empty, with no evidence of broken shells or dead chicks, indicating successful fledging.

This is the first instance at Freeholders’ Wood of nesting birds and dormice occupying the same nest box.

Fieldworkers recorded the sex, weight and breeding condition of the dormice they found.  They recorded the dormice as adults if they had orange-brown fur, or as juveniles if the fur was greyer.

Research indicates that juveniles need to reach a minimum weight of 15g by late October in order to survive their long hibernation.

The average weight of a juvenile dormouse at Freeholders’ Wood in October was 16.9g, indicating that there was a good autumn supply of nuts and berries in the wood.

This means that the young dormice were in the best possible condition for hibernation.

The report was written by the wildlife conservation officer at the Yorkshire Dales National Park Authority (YDNPA), Ian Court, and Ian White of the People’s Trust for Endangered Species

Ian Court said:  “Freeholders’ Wood is one of two sites in the National Park where Dormice are present, and overall it’s been another good year.  The spring and autumn records compare very favourably with the national data and suggest the population is doing well.

“The management of Freeholders’ Wood, which includes a hazel coppicing programme, will ensure that in the long-term the habitat remains suitable for dormice.

The monitoring work suggests that the wood continues to support a viable population.”

The full report can be seen at the YDNPA’s Nature In The Dales website: http://www.natureinthedales.org.uk/species/mammals/dormouse