Grimly the natterjack has hung on in duneland and heath on the west coast of England, in Norfolk and in Hampshire. Now Dr Trevor Beebee, of Sussex University, has come to the rescue and is breeding natterjacks in his back garden near Brighton.
'The heath and duneland that used to be occupied by the natterjack has changed. It is no longer being grazed by cows and sheep,' Dr Beebee said. 'As a result the vegetation is thicker and common toads are able to invade and compete.'
The natterjack toad, Bufo calamita, can be recognised by a bright green or yellow stripe running down its back. It is also distinguished by its habit of burrowing into sand until it reaches a moist layer where it may stay for weeks in hot weather. By contrast the common toad, Bufo bufo, which does not know how to dig holes, dries up and dies in warm air if it can find no moist shade.
The natterjack has disappeared from 70 to 80 per cent of sites where it was known at the beginning of the century. It is now known at only 40 sites in England. Dr Beebee hopes to persuade landowners to reintroduce grazing to produce the conditions that favour the natterjack. 'They need shallow ponds which dry out between seasons. Then water beetles that would otherwise eat the tadpoles do not survive in the pond.' He has built a small pond in his garden where the toads are protected by netting from birds. Some six or eight adults produce hundreds of eggs each year but even in this sheltered environment less than a dozen toads reach maturity.
'There was a severe early cold spell last year and none of the tadpoles survived in the pond in my garden,' Dr Beebee said. 'The natterjack is at the edge of its natural range in England. It is also under threat in Belgium and France but is surviving well in Spain and Portugal.'
Dr Beebee has a contract from English Nature under its species recovery programme to find ways of establishing new colonies of the toads by returning spawn, tadpoles or tiny toadlets back to the wild. In 1980 one new colony was established in Sandy, Bedfordshire, and now he is establishing others in Surrey and has plans for Dorset.
'The best way to reintroduce them seems to be to take spawn strings to the new site. Then it takes three years for the toads to grow to adult size and for us to assess how well it has worked,' Dr Beebee said. 'We are getting indications that one of the populations is beginning to take off.'