Number of dormouse found per 50 boxes checked, Surrey, 2014

How was 2014 for dormice in Surrey?

This article is adapted from one that I wrote for the spring/summer issue of the Surrey Dormouse Group (SDG) newsletter, and is reproduced here with their kind permission. It's based on data collected by dozens of volunteers across the county. If you would like to find out more about the work of SDG, visit their website

Last year SDG members checked a total of 7076 boxes from 18 sites. Data from each SDG box check gets reported to the National Dormouse Monitoring Programme, to feed into their national analyses – you can read about how 2014 was for dormice nationally in the Dormouse Monitor.  Here’s a summary of the data from Surrey.

How many dormice?

We saw a total of 487 dormice over 2014. That works out at a mean average of 3 dormice per 50 boxes checked, but there was quite a range of numbers seen at box checks: from 0 per 50 boxes to 27 per 50 boxes. At a third of box checks no dormice were found. The median number of dormice found per 50 boxes checked was 1, which is probably a representative average, given that a few large numbers are skewing the mean. Some sites that had quiet starts to the season saw large numbers later on. On average, we also found 2 empty dormouse nests per 50 boxes (ranging from 0 to 18).

Number of dormouse found per 50 boxes checked, Surrey, 2014
Number of dormouse found per 50 boxes checked, Surrey, 2014

When did we see them?

The earliest dormouse was a 20g torpid male, found on the 6th March, and the latest ones were 3 found at the beginning of December (that’s not to say others weren’t around earlier or later – just we weren’t checking so didn’t find them). As you can see from the graph above, average numbers were highest in August to October, and lowest in March and April.

How much did they weigh?

Females weighed slightly more on average than males (19g vs 18.7g), but this changed considerably over the course of the year, as you can see from the graph, with weights at their highest just before hibernation. The heaviest dormouse recorded was a 33g female found in October.

Average weight of dormouse found in Surrey, 2014
Average weight of dormouse found in Surrey, 2014

Other interesting features

Dormice with white tail tips were reported 36 times over the year, including a family of juveniles, all with white tail tips. There were 9 dormice with stubby tails.

Youngsters

The earliest pinkies were found on 20th July. (Pinky is a technical term describing baby dormice before they grow fur). On that same box check the earliest greys (babies that have their first coat of fur, which is much greyer than an adult) were also found. The latest pinkies were found on 25th September, and the latest greys were found on 20th October. Dormice born later in the year have more of a struggle to fatten up in time for hibernation, but those born too early in the year may struggle with their mother not being able to find enough food for herself.

The largest number of dormice found in one box was 8 (mother with young): boxes with 8 dormice were found at two sites.

Other box occupants

Apart from birds (which seem to take over a large number of boxes in spring at some sites) and invertebrates, the most common other occupant were wood mice (162 were seen, 21 of which were found in dormice nests) and yellow necked mice (29 were seen, only one of which was in a dormouse nest). There were also 12 unidentified apodemus mice (wood mice or yellow-necked mice). The rarest other box occupant was the pigmy shrew, with only 7 reported over the whole year (2 of which were in one box).

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