TWO of Britain鈥檚 native crickets have been rescued from almost certain extinction through a captive breeding programme at London Zoo. The programme has been so successful that the cricket team has established several self-sustaining colonies in the insects鈥� former haunts.
In 1991, the field cricket (Gryllus campestris) survived at just two places in Sussex. There were only 30 breeding females left in the wild. The wartbiter cricket (Decticus verrucivorus) was found at only three British sites.
In 1992, six male and six female field crickets were captured as part of a species recovery programme run jointly by conservation specialists from English Nature and invertebrate experts from London Zoo. Most of the 4000 crickets bred from the original 12 have now been released at carefully chosen spots in Sussex, Surrey and Hampshire. There are now six self-sustaining colonies, says Patricia Croft of the zoo鈥檚 invertebrate house.
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Two batches of captive-bred wartbiters have been released at one site in the south of England, and the species is now on the road to recovery.
The field cricket likes rough, acid grassland. It digs a burrow in the turf, making a distinctive platform at the entrance where the male stands to 鈥渟ing鈥� and bask in sunshine. Field workers keep track of the crickets by counting their burrows and listening for the male鈥檚 song, says Dave Shepherd of English Nature, who runs the cricket recovery project. 鈥淚t鈥檚 not the most reliable method,鈥� he says, 鈥淏ut it鈥檚 the best we can do.鈥�
Croft and her colleagues at London Zoo are now planning a captive breeding programme for the even rarer mole cricket, Gryllotalpa gryllotalpa. They are experimenting with mole crickets collected in Guernsey to find the best way of rearing them before they release any into the wild. But the cricket team could be stumped before it starts: so far, it has failed to find a single mole cricket on the mainland.
All three species are on display in London Zoo鈥檚 Native Insect Exhibit, which opened last week.