Monday 5 September 2016

Dormouse Project, 1982-1994 and the first release of captive-bred dormice in the UK

A Talk by Dot Eaton to the Berkshire Mammal Group
3 March 2016

Over thirty years ago Dot was an animal keeper near Loch Lomond, when she formulated an ambition to build a captive-bred stock of British animals and reintroduce them to the countryside, but was warned there would be significant difficulties. Each animal would have to be vet-checked, landowners’ permission would be required, and some animals simply couldn’t be bred in captivity. However, she took heart from Gerald Durrell’s private assistant John Hartley and settled on dormice as her preferred species. At the time there was only one book on the subject, Common Dormouse by Elaine Hurrell, the daughter of Harry Hurrell. Eventually Owen Newman, a BBC cameraman, was recommended to her as someone with relevant expertise; someone who recently had even filmed a dormouse giving birth. It was Owen who trapped her first dormice at a location in Wiltshire, giving Dot three while retaining two for his own use. Dot had, by this time, qualified for a licence and Owen give her other dormice on subsequent occasions.

Dot’s first breeding colony
In 1982 she moved to Chessington Zoo and started breeding her first colony, and when she relocated to Windsor Safari Park in 1988 she moved her dormice with her. She had a small shed, divided into four and fitted with a central red light, but something larger scale was required and Dot designed a new breeding unit. The journal Robin Page visited and wrote a very supportive article in Country Life, helpfully ending with an appeal for funds. A cheque for £2,500 duly arrived from Mrs T. Hesketh of the Valerie White Trust, and the new building was erected. It had eight enclosures divided by Perspex to prevent the transmission of disease. In each enclosure was paced one male and one or two females – 16 animals in all – and Dot filled them with fresh branches twice a week: Hazel, honeysuckle and rosebay willowherb. She had red lights fitted to allow her to observe the dormice from a adjoining corridor and thus improve her understanding of their behaviour and ecology.

Observations of dormice
Their first reaction on Dot entering the enclosure was to freeze stock-still. They weren’t particularly sociable and didn’t feed together. Rather, if the encountered each other, the dominant individual would maintain its place and the other would run away (and surprisingly fast). Consequently Dot realised that food supplies had to be distributed widely throughout the breeding unit. Having said that, several dormice would share a nest box; perhaps three or four together. Sadly she never saw the process of nest building – presumably as they were inside the nest-boxes – but she did see dormice stripping branches in preparation and stuffing soft honeysuckle bark into their mouths before taking it to a box. There are several nest types: two or three-leaf nests made by juveniles; round nests full of bedding as breeding nests; and semi-subterranean grapefruit-sized nests in which to hibernate. The latter are at ground level and built partly into scrapes to achieve as stable a temperature in winter as possible. The adult dormice emerge in May in time to breed. They run and chase each other for three nights before finally mating. Then, if pregnant, the female will retire to a nest after 30 days to give birth. After a further 30 days the juveniles appear. (If not pregnant the chasing resumes after about 10 days, but most litters are early.) When the juveniles emerge it is fascinating to observe their varied personalities and the mistakes they make. They don’t know to freeze and they miss branches when climbing; Dot realised they are very vulnerable in the early days of life. Indeed if the temperature falls to blow 10 oC for several concurrent nights, then – assuming the juveniles are not fully developed – the mother will go torpid and the youngsters will die. As a result there may be second litters to replace the losses. In mid August the adults fatten up to hibernate; the youngsters take longer to prepare for the winter sleep.

The reintroduction team
Dot realised that a number of skills were necessary for success, many of which she personally didn’t have, and so assembled a team of experts to help.
  • Martin Hicks
Ecologist in Hertfordshire
  • Dr John Lewis
Vetinary surgeon
  • Julian Ford-Robinson
Senior Science Master, Haileybury College
  • Prof John Gurnell
Behaviourologist at QMC, London
  • Steve Whitbread
Tracking specialist, Southampton University
  • Dot Eaton
Dormouse breeder

IUNC Guidelines
These govern captive breeding for reintroduction projects worldwide and are founded on several fundamental principles:

  • There should be evidence of former occurrence
  • The causes of previous loss should be understood and a result of human action
  • The factors causing extinction are to have been rectified
  • The proposed habitat should be suitable and of sufficient extent

All of these were met at the proposed site at Haileybury in Hertfordshire, as though the site was small (7 hectares), two substantial hedgerows linked it to extensive woodland nearby.

1992: The Reintroduction
On 18 August the dormice were placed in a cage and observed until 23 September when the hatch was raised. One dormouse ventured out along a branch and returned. Within half an hour the colony had moved into the wild. There were two family groups: a male, two females and two young in one, and one female and five young in the other. One juvenile was radio tracked and was found to have ranged 35m and back. Three others ranged by a similar amount that first month. (Perhaps the rest did too, but only some individuals were monitored.) Five more juvenile males were added the following year, and more the year after.

Further observations
It was apparent that the dormice liked to explore and spent little time on the ground. Their squeaking is much like that of a mouse

1994: Burnham Beeches
In 1994 Windsor Safari Park went into receivership and despite efforts to sell it as a going concern, it was finally sold for development as the new Legoland. Employees, including Dot and her husband, were evicted from their tied cottages. As well as the loss of her home, Dot had 97 animals to care for. Initially the dormice were taken to St Tiggywinkle’s, and then to Burnham Beeches were they and the breeding unit were offered a home by Mark Frater and Helen Reed, the keeper and ecologist there. Indeed, as well as feeding and looking after the dormice, Mark and Helen even built a second breeding unit. Eventually Dot arranged for a contract to assign ownership jointly with the Corporation of London (owner of Burnham Beeches). With others expressing an interest in the project, a Common Dormouse Captive Breeders’ Group was formed and continues to function to this day. Since 2000 the reintroduction programme has been administered by the People’s Trust for Endangered Species, which has now run as many as 25 such projects (involving partners such as London and Paignton zoos). Meanwhile Dot has been invited to speak at international conferences in Denmark and the USA, though without her own facilities, she is no longer been active in breeding dormice.

To which Martin Hicks, present in the audience, contributed.

Taxonomy – dormice are a group of their own, with two species in the UK: Common and Edible.

Breeding – litters of 2-6 juveniles. They remain in family groups for a while, both parents looking after the youngsters. Pairings are temporary, however, as dormice are quite promiscuous.

Physical characteristics – include a semi-prehensile tail and forward facing eyes

Behaviour – they are arboreal and nocturnal, but particularly active at dusk and dawn. They hibernate throughout the long winter months, though in Mediterranean countries the higher temperatures require much less hibernation. When torpid or hibernating, they are vulnerable to ground predators, such as badgers and wild boar, though dense vegetation protects them from the attention of owls. Their food supply, however, is adversely affected by the presence of the more vigorous grey squirrel.

Habitat – not just coppiced hazel, although that is most characteristic and 2-3 year old coppice is ideal, they will even be found at the edge of pine forests and where there is dense vegetation. However, it is habitat loss that has been the biggest cause of their decline; the loss of managed woods with lots of new growth, and the ripping out of hedges has isolated and exposed them. There has been massive change in the British countryside over the past century.
Edwin A.R. Trout
Berkshire Mammal Group

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