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Abstract. Tortoises of the genus Pyxis have limited ranges along the southwestern coast of the
island of Madagascar. The genus includes P. planicauda and P. arachnoides. Both species are listed
on CITES Appendix I and have been assessed as Critically Endangered for the IUCN Red Data List
in 2008. Previously, large numbers of both species were exported from Madagascar during 2000
and 2001. A naturally low reproductive rate and an increased rate of habitat loss have generated
concern over the status of these species in the wild and in captive collections. Both species are native
to tropical dry forests with pronounced wet and dry seasons. An understanding of the climatic and
environmental conditions experienced by these species in the wild is important in the establishment
of a successful captive breeding program. Replicating the seasonal cycles and maintenance of a dry
season aestivation period for adults appears important for successful reproduction in captivity. Pyxis
eggs typically undergo an extended embryonic diapause that likely corresponds to the lengthy dry
season in their native range. High hatching rates have been achieved in several captive colonies by
exposing fertile eggs to cooler and drier conditions. A shift back to warmer and more humid conditions
appears to trigger, or reinitiate embryonic development. An embryonic diapause controlled by
environmental cues may serve to synchronize and delay hatching until the following wet season. Soil
temperature data collected at three sites in Madagascar provide guidance for incubation protocols
in captive collections. Current conservation measures include AZA studbooks and Species Survival
Plans. Long-term success of existing assurance colonies will require continued cooperation between
zoological institutions and private breeders.
