Table Of ContentMemoirs ofthe Museum ofVictoria 56(2):587-589 (1997)
AN EXSITU BREEDING PROGRAMME FOR THE ENDANGERED UK POPULATION
OF THE FIELD CRICKET GRYLLUS CAMPESTRIS
Paul Pearce-Kelly, Pat Croft, Paul Atkin and Dave Clarke
Invertebrate Conservation Centre, Zoological Society ofLondon, Regent's Park, London NW1 4RY. UK
Abstract
Pearce-Kelly, P., Croft, P., Atkin, P. and Clarke, D., 1997. An exsitubreedingprogramme
for the endangered UK population ofthe field cricket Gryllus campe&tris. Memoirs oftin-
Museum ofVictoria 56(2): 587-589.
In 1991 the British population ofthe field cricket Grylluscampcsinswasclose toextinc-
tion with fewerthan a hundred individualsremainingin thesinglesurvivingcolony. A key
componentofEnglish Nature'srecoveryprogrammeforthespeciesinvolvedthecreationol
six new colonies in areas ofthe cricket's former UK range. This objective required the
establishment of a captive-breeding programme to provide the large number ofanimals
needed to found the new colonies. Between 1992 and 1995 >4000 captive-bred nymphs
were released into five new sites. Monitoring confirmed that the release populations are
becoming successfully established.
Introduction Nature has placed the field cricket onto its
Species Recovery Programme. This conser-
By virtue oftheir small size, modest accommo- vation initiative is directed at recreating the
dation requirements and often substantial cricket's habitat requirements over areas of its
reproductive potential, many invertebrate formerrangeandidentifyingexistingalternative
species can be maintained as large captive sites that already provide suitable habitat.
populations retaininglevelsofgenetic variation In autumn 1991 English Nature (EN) and the
necessary to achieve successful field re- Zoological Society ofLondon (ZSL)agreed on a
introduction and establishment (Morton, 1991; protocol to establish a captive-breeding pro-
Pearce-Kelly, 1994). Experience has also shown gramme, based at the London Zoo's Invert-
that invertebrate conservation programmes can ebrate Conservation Centre, to support EN's
holdtheirownwhenitcomestogeneratingpub- ongoing Species Recovery Programme for the
lic interest and support. These considerations field-cricket. The protocol involved using wild
makemanyinvertebratespeciesexcellentcandi- caughtcricketsfromthesolesurvivingmainland
dates for receiving captive-breeding assistance colony to provide a founder breeding stock to
as part of conservation programme work. An produce the large numbers of captive bred
example of the efficacy of providing captive crickets required to populate new colony sites.
breeding assistance to an endangered invert- In the late springof 1992, six pairs ofsub-adult
efobrrattehespUecKiespoisputlhaeticoonnseorfvatthieonfipelrdogcrriacmkemte, wfiiellddccroilcokneytsinweWreestcoSlulsescetexd(fErdwoamrtdhse,r1e9m9a2i)nainndg
Gryllus campesths L.,1758. taken to the Zoo's Invertebrate Conservation
Although a relatively common species on the Centre.
European continent, by 1991 the British popu-
lation of G. campestris had been reduced to a Captive-breeding and rearing conditions
siEinnngdgfaleenwgseeurrrvteihdvaiinnng1t0hc0eoliBornnidtyiivsiihnduWRaeelsdstaDSnaudtsasiseBxro,eocnkour(mdSbeheidrrat-s, wUeproenianrirtiivaalllyatketphte Zsoepoartahteesuibn-apdlualstticcritcaknektss
U19K87)w.asTheessernetaisaolnlyfloorstshoefsiptseccileossedegcrloiwnienignttuhref s1t8erxil3i3sexd 1I8mcmmshNiog.h.2Tphoettsiunbgstsorialtetocoansdiespttehd ooff
sspiortieilsm,aenwdhcaitucoshehnaoevfeedtahtisoshbehleatbseiirtteaudtatalenoddssosnhuanpsnoyrboeauessnpescoatvn.edrAy- e(1cn2occlomlue.rctaEegadechfttrhaeonmkcrwitachskeeptsorroitvgoiidneeaxldcwacivotalhtoeanysaodbsiuotrefr)touwtr,of
growth of vegetation, as a result of changes in which they readily did. Drainage holes in the
gbsruearrzvioinfvgicnopglroaUncitKeiscp,eso.tphuIelnactaoinnosneefrafvnoardttietoxonpsabanofddeygtuhaEerndngluitmsh-he cborafiscetkheotefstwshueebrstetarnpakatsie.raeldlUoupwpoendinfotrrheeafcrsheaiqmnugeenttaadnwukalstt.eritnhge
587
588 P. PEARCE-KELLY ET AL.
Temperature and humidity levelswereaimed colonysites selected by English Nature. Priorto
at mimicking the recorded field conditions as release the different progeny lines were amalga-
faithfullyaspossible. In additiontomaintaining mated soasto ensuremaximumgenetic mix for
a fluctuating day/night background tempera- colony establishment.
ture, a 60 watt light bulb was suspended over Regular monitoring of the introduction sites
eachofthebreedingandrearingtankstoprovide has confirmed the successful overwintering of
radiant basking opportunities. The bulbs were sufficient numbers of the captive-bred crickets
on from 09.00-12.00h and from 13.00-18.00h to ensure the production ofthe Fl wild gener-
which elevated maximum temperatures to the ation. These Fl crickets have in turn gone on to
low 30s (°C). At night the room temperature produce the F2 wild generation (Edwards,
dropped to 15°C. Mean humidity levels in the 1995).
rearing tanks was approximately 50%. In additiontoprovidinglargenumbersofani-
Matedfemalesovipositeddirectlyintothesoil mals for colony establishment, the captive-
substrate ofthe breeding tanks. Upon hatching, breeding programme is helping to clarify some
nymphs wereleft in the breedingtanks until the important biological questions, such as sex
2nd or 3rd instarwhen they were transferred to ratios and fecundity data, that would otherwise
nymphal rearing tanks 30 X 45 X 30cm high. beimpossibletoascertain. By summer 995 the
The rearing tanks were provided with 6 card- results ofthe field cricket recovery pro1gramme
boardeggtraysstackedatoneendofeachtankto were such that English Nature was able to
maximiseopportunitiesforsuccessful moulting, declare the species secure in the UK.
basking and shelter. Care was taken to ensure
that offspring of different females were
Conclusion
maintained as separate progeny lines.
The overwintering requirements of the Thecaptive-breedingprogramme forG.campes-
crickets were best met by exposing the nymphs tris highlights how successful and cost-effective
to the rigours of a British winter. This was such conservation work for invertebrate species
achieved by placing nymphs in unheated exter- can be. By allocating even modest resources to
nal insect rearing units, either in their rearing develop captive-breeding programmes for
tanks or into 1.5 m-square external bays with a invertebrates facilities, such as zoos can signifi-
deep soil and turf substrate to allow more cantly increase theirability toplay a major role
natural overwintering conditions. in species conservation (Pearce-Kelly, 1994).
The crickets were presented with a variety of
vegetables, fruits, leaves and grasses with the
Acknowledgements
most popular food items being fresh lettuce,
apple, and carrot. Bran and cuttlebone (a cal- The authors are indebted to English Nature for
cium supplement) were also provided. Females generousgrant support forequipment and staff.
were occasionally given the larvae of the wax The advice and support ofMr Mike Edwards is
moth, Galleha mel/onella which were often also gratefully recorded.
accepted. The provision of fish-flakes mid way
through the programme was seen as an import-
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