Demography and conservation of the Floreana racer (Pseudalsophis biserialis biserialis) on Gardner-By-Floreana and Champion Islets, Galápagos Islands, Ecuador : thesis submitted in partial fulfillment of the requirements for the degree of Master of Natural Science

Abstract

The Floreana Racer (Pseudalsophis biserialis biserialis) is a mediumsized colubrid endemic to the islets of Gardner-by-Floreana and Champion off the coast of Floreana Island, in the South of the Galápagos Archipelago. The subspecies was historically abundant on Floreana Island, as indicated by subfossil remains, however is has since been extinct there since the late 1800’s as a result of the effects of large-scale habitat modification, fires and the introduction of rats and cats. I conducted the first field study on the population size, inter-island morphological variability and the diet of the Floreana racer on the two islets where the species occurs as a first step towards the translocation of Floreana racers to Floreana Island. Fieldwork took place over 30 days between November 2015 and January 2017. With the assistance of eight colleagues and volunteers I conducted daylight searches for Floreana racers yielding a total of 123 individuals, 20 on Champion and 103 on Gardner-by-Floreana. Of these 119 individuals were marked with unique PITTags. I also conducted a mark-recapture estimate of population size on both islets based on 17 recaptures. The resulting estimate of the global population of the subspecies is approximately 3088 individuals (Champion 209 snakes; Gardner-by-Floreana: 2879 snakes). I also investigated the diet of Floreana racers via analysis of faecal samples from 29 individuals. The most common prey items are lava lizards (Microllophus grayii), followed by the Floreana gecko (Phyllodactyllus baueri). Lastly I discuss the conservation status of the subspecies and future areas of research and management to advance the knowledge, and conservation status of the Floreana Racer.