NHBS Guide to Dormouse Survey Equipment

Dormice are a distinctive family of rodents, found widely across Eurasia and Africa. The Hazel Dormouse (Muscardinus avellanarius) is a native British species which resides primarily in deciduous woodland. They are protected by EU law because of their rapidly declining numbers – studies suggest they have suffered a 72% population reduction in the last 22 years. Dormice are an important bioindicator as they are particularly sensitive to habitat and population fragmentation, so their presence is an indication of habitat integrity.

To enforce legal protection and ensure the success of conservation projects, current data about the distribution of Hazel Dormice is very important. A variety of survey equipment and methods can be used by licenced dormouse handlers and wildlife enthusiasts.

Nest Boxes

Perhaps the simplest survey technique to determine dormouse presence is searching for the nest box residents. Dormouse nest boxes are largely similar to standard bird boxes, but with the entrance hole facing the tree. Nest boxes can be important conservation tools as they can boost the local dormouse population density and aid re-introduction schemes.

The Standard Dormouse Nest Box is built from FSC softwood and has a removable lid with a wire closure for monitoring. This box can also come with a perspex inner screen allowing  surveyors to check the boxes inhabitants, without the risk of escape or  injury.

The more resilient Heavy Duty Dormouse Box is made from thicker  ¾” FSC marine plywood and is ideal for long-term monitoring projects. 

Dormouse Tubes

Dormouse nest tubes are a cheap, easy and popular method of determining the presence of dormice within a habitat. They can be an effective alternative to using wooden nest boxes.

The tubes consist of a wooden tray and a nesting tube. Dormice make their nests in the tubes and it is these that are used as indicators of their presence in the habitat. Nest tubes can be set up and checked without a licence until the first evidence of dormouse activity is found. After that, only a licensed handler can check them. For attaching to a tree, Hook and Loop Strapping is a more environmentally friendly alternative to plastic cable ties, as they are reusable, reducing plastic waste.

Dormouse Footprint Tunnels

The latest dormouse surveying technique uses footprint tunnels. This technique was created by Suffolk Wildlife Trust with PTES funding and has since been recommended in the CIEEM magazine In Practice in September 2018.

It is a non-invasive survey technique, which does not require a licence as the chance of disturbing dormice is very low. The 40cm tube, houses a wooden platform which contains the charcoal ink and paper on which footprints are left. Compared with nest tube surveys, footprint tunnels can reduce the survey period required and provide an indication of the presence or likely absence of dormice at a site.

Dormouse Nut Hunting

Dormice leave very characteristic marks when they eat Hazel nuts. They gnaw a round hole in the shell leaving a smooth edge with very few teeth marks, unlike mice or voles. Systematic nut searches under Hazel trees are still regarded as one of the best survey techniques, only hand lenses and a keen eye are required.

Accessories and books

Below are some accessories and books that are commonly used for dormouse surveys and monitoring:

Small Mammal Holding Bag
£3.60
Pesola Light-Line Spring Scales
From £35.00

Pesola PTS3000 Electronic Scale

£126

Heavy Duty Extra-Large Polythene Sample Bags
£0.70 per bag

Animal Handling Gloves
£5.69 5.99

LED Telescopic Inspection Mirror
£11.99 

How to Find and Identify Mammals
£11.99

Britain’s Mammals: A field guide to the mammals of Britain and Ireland
£12.99

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Dormouse Nest Tubes – fast, secure placement

How have we improved our dormouse nest tubes?

dormouse tubeWe have just released a new and improved model of the dormouse nest tube. What’s different? Well, we have tried to tackle two of the most frequently encountered problems with setting up dormouse nest tubes. (1) It can be tricky to attach them securely to a branch and (2) once ‘securely attached’ they are prone to slipping. To reduce these issues we have added retaining loops to the base of the nest tube to stop slippage and to enable faster placement.

We also supply 71cm cable ties for fast set-up. If you prefer using garden wire to secure your nest tubes then this method will also be easier using the new loops.

Dormouse survey – best practice

hazel dormouseFor the non- (or new) professionals out there a few quick pointers on best practice for a survey using dormouse nest tubes.

  1. Surveys should not be limited to habitat perceived as ‘optimal’ but should be undertaken in any areas of affected woody habitat (including adjacent areas if the impact of development is likely to extend beyond the site footprint).
  2. Normally at least 50 nest tubes should be placed at roughly 15-20m intervals and these should be left in place (and checked monthly) for the majority of the active season.
  3. In order to have any chance of obtaining a license to carry out work affecting dormouse habitat you must first conduct a survey with a probability of 20 or above of finding dormice if they are present (although please remember that an absence of evidence is not evidence of absence). To calculate the probability score for your survey you add together the scores (Table 1) for the months during which the survey was conducted (for surveys conducted using 50 dormouse nest tubes and following the advice given in points 1 and 2 above).

dormouse survey results

 

 

 

 

 

Taken at face value this means that all dormouse surveys should begin by June at the latest; however, it is possible to start a survey later than this under certain conditions. For example, you can increase survey effort by increasing the number of dormouse nest tubes deployed (if you use 100 tubes you can double the scores in Table 1). Note though that surveys conducted using a large number of tubes for a short period are not good practice and nor are surveys where tubes are crowded together at intervals of less than 15-20m (although 10m intervals may be acceptable in very small sites).

For further details we recommend you consult the latest guidance from Natural England in England or your national licensing authority (e.g. Countryside Council for Wales, Scottish Natural Heritage, etc.).

Dormouse resources:

The Mammal Society

Dormice: A Tale of Two Species jacket imageDormice: A Tale of Two Species
Pat Morris

 

 

 

Living with Dormice jacket imageLiving with Dormice
Sue Eden

 

 

Dormouse survey products:

dormouse nest tubeDormouse nest tubes

 

 

Standard Dormouse BoxDormouse box