Dormice

During October, visitors to Norsey Wood may have seen me thrashing through the undergrowth, locating and checking the numerous dormouse boxes installed around the reserve. Of the 112 boxes installed across the Wood since 1998, I managed to find 100. Six contained a dormouse nest, all but one with animals present. Two nests contained lone males, and the other three a female with young. Across the whole Wood the occupancy rate of 6% seems fairly low, but on an area-by-area basis those areas where dormice were found had occupancy rates of 20% and higher.

The dormouse (Muscardinus avellanarius) is one of our most elusive native mammals. Also known as 'the seven sleeper', it is perhaps best known for the amount of time it spends asleep. As days become shorter and the weather colder, the dormouse makes a nest at ground level, where it will hibernate through the winter. Dormice emerge around April, when the weather is warmer and food is abundant.

Historically it was thought that the dormouse relied on hazel as a main food source. This does not appear to be the case, however: dormice have been found in habitats with little or no hazel present. For example, one thriving colony has been identified in a coniferous plantation! The dormouse will eat a wide range of things - flowers, nuts and berries - and its reliance on insects has been realized as being more significant.

It is during the summer months that dormice use the boxes we have put up for their breeding nests. They can weave their own nests in bushes and shrubs, but they prefer nesting places such as hollow tree branches. Since they are mainly nocturnal and tend not to come to ground level, our best chance of assessing their presence is by offering an attractive summer residence (a dormouse box) in preference to a natural nesting site. In areas where dormice are known to be present, this also enables us to monitor populations more closely. The optimum month for monitoring dormice is October, when the adults have bred and the young are fattening up for their winter sleep.

ln the UK the dormouse is restricted mainly to England. However, it is an animal under threat. In the past 100 years it has become extinct in seven counties (half its former range). Dormice live at a very low population density and are slow to adapt to change. The main factor in their decline appears to be loss and fragmentation of suitable habitat. Dormice prefer woodland with a good understorey of shrubs and bushes to provide food and shelter, and arboreal links are vital to allow the animals to move around their territory. Although coppicing provides a good habitat, it takes about five years from cutting until it is suitable for these mammals.

The low occupancy rate in some areas of Norsey Wood may be attributed to a number of factors. In the areas chosen, the habitat is generally good but the boxes are very exposed, making the trip from foraging areas to the box hazardous.

Due to its rarity, the dormouse is protected by a number of national and international laws, and to monitor dormice it is necessary to be licensed by English Nature. The dormouse has been identified as one of Basildon's Biodiversity Action Plan species. A series of measures are being taken to conserve those populations present and identify other populations across the District, as well as maintaining the desirable habitat. The survey work at Norsey Wood forms part of this. It is a condition of the licence that all survey information is collated and sent to the national recording office, so this work helps build the national picture of remaining populations.

During the early part of 2002 I shall be going out with volunteers from the work party, cleaning and maintaining the boxes around Norsey Wood, in good time for the emergence of the dormice from their winter sleep. So if you would like to help on the conservation of this rare mammal, come along to a work party and lend a hand.