Natural hazel dormouse nests
Where hazel is absent, other signs of dormice must be sought, such as nests. They may weave their own nests, which are up to the size of a large grapefruit and usually sited in low growing shrubs. A survey undertaken by Hurrell between 1975- 1979 showed that natural nests were most likely to be constructed using grass and leaves but honeysuckle bark was also a frequent component. Bramble was by far the most important shrub as a nest supporting plant with a total of 42% of nests recorded in bramble.
These are often collected fresh and are either green or faded to grey. The nests are spherical and lack an obvious entrance hole. Searching for nests is time consuming and often unsuccessful – even where dormice are known to be present – as they mainly use other places to rest (for example, tree holes) and do not often construct nests of their own. Thus, failure to find woven nests should not be used as evidence of absence.
This survey below was before dormouse nest boxes started to be erected in woodlands but bird nest boxes were the next most frequent dormouse nest support.
The average height of nests recorded above the ground was found to be just over one metre but the majority of nest recorded in bird boxes were between 3-5 metres high.
While looking for natural nests can be a very useful way to detect dormouse presence, there is no quantifiable method linking the time spent searching to the likelihood of find a nest.
Nest boxes are a particularly attractive substitute for natural tree holes and, where boxes are provided, a high proportion of the dormouse population may use them. Dormice can make a range of nest within nest boxes and the key features that suggest dormouse activity, are the presence of a number of green leaves in the box that have been brought in from afar, and/or the presence of a tightly woven vest.
Dormice will also make nests in nest tubes and due to their smaller internal space, these can sometime be quite hard to identify. However, the key features remain the same.
Dormice usually spend the winter alone in a small tightly woven nest. They hibernate under logs, under moss and leaves or among the dead leaves at the base of coppice stools and thick hedges. Dormice choose a moist place to hibernate, where the temperature will remain cool and stable and the humidity high. Damp, cool conditions are vital as metabolic processes are slowed at lower temperatures and fat reserves will then last longer. Water vapour is lost during the animal’s breathing and so damp conditions are necessary. Hibernating in a moist place will ensure the animals do not desiccate during the winter, as they do not wake up and drink regularly
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