Investigating the Role of Toxicological, Nutritional, and Infectious Diseases in the Decline of the Critically Endangered Christmas Island Flying-Fox (Pteropus natalis)

Abstract

Over the last 30 years, the Christmas Island flying-fox (CIFF; Pteropus natalis) has declined from approximately 6,000 individuals in the 1980’s to 3,800 individuals today. While the cause of contraction of the CIFF is not well understood, several disease related threats have been proposed. Potential diseases include intoxication with cadmium, nutritional diseases resulting from foraging on introduced plants, and diseases caused by infectious agents. The primary objective of this thesis was to understand disease related threats to and inform best practice management policies for conserving the CIFF population. In this body of work, I examine the utility of flying-foxes as bioindicators for metal pollutants and validate minimally-invasive sampling methods for screening flying-foxes for metal pollutants. Using these validated sampling methods, I identified increased cadmium concentrations in CIFFs. Urinalysis, biochemistry, and histopathology of a subset of CIFFs with paired cadmium data revealed proteinuria and glucosuria in two CIFFs and possible bone lesions in one CIFF suggesting cadmium exposure may have substantial implications for the health of the population. To explore nutritional diseases, I determined essential nutrients of native and introduced food plants consumed by the CIFF. Examination of nutrients revealed how the CIFF historically met their nutrient requirements. I then predicted how preferentially foraging on introduced plant species might alter nutritional requirements. Lastly, using multiplex serological and molecular assays I demonstrate the presence and maintenance of a Tioman-like and a severe acute respiratory syndrome-like coronavirus in the CIFF population. This has implications for understanding viral maintenance in small, geographically isolated bat populations. Together this work substantially contributes to our understanding of health-related threats to the CIFF and by extension other insular flying-foxes facing similar threats.