Watching Extinction Happen: the Dramatic Population Decline of the Critically Endangered Tanzanian Turquoise Dwarf Gecko, Lygodactylus williamsi

Abstract. The turquoise dwarf gecko (Lygodactylus williamsi) is endemic to two small forests in eastern Tanzania, where it exclusively dwells on screwpines (Pandanus rabaiensis). To assess its population status, we surveyed its habitats at the Kimboza Forest Reserve and (under different assumptions) estimated the population size of the territorial L. williamsi based on habitat availability, using Pandanus abundance as a proxy. Furthermore, threats to the species, especially the impact of the international pet trade on the population, were studied. Our results suggest a severe population decline, as the observed population size is one third smaller than its potential size based on habitat availability (i.e., Pandanus). We estimate that in a period of four and a half years, at least 15% of the potential population were collected for the pet trade, making it a major threat to L. williamsi next to habitat degradation. Based on our results, we consider this species to be threatened with extinction (Critically Endangered).