Conservation of the Central Galapagos racer (Pseudalsophis dorsalis) in the Galapagos Islands, Ecuador : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Conservation Biology, Massey University, Auckland, New Zealand

Abstract

Snakes (Reptilia; Squamata) remain one of least studied vertebrate groups, in spite of recent field studies on various regions and taxa. This is due in part to logistical difficulties associated with studying these ectotherms in the field, and also the low density of some populations which prevents the collection of multi-year large datasets across large geographic areas. Island species and populations of snakes offer a unique opportunity to document aspects of diet, distribution and intra-population phenotypic variability that can inform conservation practices. In the Galapagos Islands, there are nine species of endemic terrestrial snakes, collectively known as “racers” (Pseudalsophis spp.). In recent years, there has been a surge in the public interest on these reptiles, which has also been accompanied with an increased need by managers to develop conservation programs for threatened populations. Unfortunately, there are still significant gaps in knowledge regarding the basic biology of these snakes. The central Galapagos racer (Pseudalsophis dorsalis) is one of the most widespread and variable species, with a historical distribution that includes the islands of Santa Cruz, Santa Fe, Baltra, Seymour Norte, and several islets < 100 ha in size off the coast of Santa Cruz Island. Anecdotal information suggests that the species has disappeared from most of Santa Cruz Island, possibly due to predation by introduced mammals. The Directorate of the Galapagos National Park, in collaboration with Massey University and Island Conservation has identified priority areas of research to advance the conservation of the Galapagos terrestrial snakes in general, and of the Central Galapagos racer in particular. In this thesis I provide an overview of the historical distribution of the species and an analysis of the dietary diversity of central Galapagos racers at various sites. I also present the results of a preliminary analysis of the colour variation of the Seymour Norte population and the similarities and differences in colour pattern of the Santa Fe, Baltra and Seymour Norte populations. I also describe a population of central Galapagos racers on the islet El Eden, a site where the species occurrence had not been confirmed since the 1980s. Finally, I present a range of key knowledge gaps and recommendations for the conservation of the Central Galapagos racer and other terrestrial Galapagos snakes. The COVID-19 pandemic had a profound effect on my ability to complete data collection in the field during the 2020 field season. Nevertheless, in this thesis I present novel information that can assist the Directorate of the Galapagos National Park in its task to preserve the bio-heritage of the Galapagos Islands.