Reintroducing Extinct in the Wild reptiles

Trial releases of critically endangered lizards on Christmas Island.

May 13, 2024

Dr. Jon-Paul Emery and colleagues conducted experimental releases of the Extinct in the Wild (EW) blue-tailed skinks (Cryptoblepharus egeriae) and Lister’s geckos (Lepidodactylus listeri) on Christmas Island. These endemic reptiles disappeared from the wild following the establishment of the invasive common wolf snake (Lycodon capucinus) on the island in the 1980s. In 2018–2019, 170 skinks and 160 geckos were released into a predator-free area after which they were monitored with robust design mark-recapture surveys for one year post-release.

Quantecol got involved with the analysis of the survey data, where we built a continuous time Jolly-Seber model to estimate per-capita recruitment, mortality rates of juvenile and adult skinks and geckos, and population sizes. Blue-tailed skinks flourished with high survival and recruitment rates leading to an increasing population size. Unfortuantely, Lister’s geckos did not fare so well with a steadily decreasing population size and no evidence of recruitment.

The work was published today as an Open Access article in Animal Conservation and represents an important contribution to conservation science.