Masters Thesis

Comparison of Habitat Use and Movement Patterns of Native and Invasive Frogs in a Grassland

Research on animal movement patterns and factors that influence these patterns is vital to conservation of endangered species. The California Red-legged frog (Rana draytonii) is a threatened species native to California. Their rapid decline has been largely attributed to habitat loss and introduction of invasive species, including the American Bullfrog (Lithobates catesbeianus). The aim of this research was to compare the nocturnal habitat use and seasonal movement patterns of R. draytonii and L. catesbeianus. I conducted a radio telemetry study in Sonoma County, California and mapped the locations of 13 L. catesbeianus and 51 R. draytonii from May 2017 to June 2018. Using a mixed model, I evaluated the effects of species, sex, size and rainfall on frog movement rate and compared habitat use relative to a water source. Within this model species, size and sex were found to have significant effects on movement rate. Rainfall was not found to have a significant effect on movement rate for either species. When comparing nocturnal habitat movement, I found that in the summer months species occupy different places relative to water sources in a creek environment; R. draytonii position themselves higher and further away from the nearest open water than L. catesbeianus. My work suggests that there are significant differences between the seasonal movement patterns and nocturnal habitat use of native R. draytonii and invasive L. catesbeianus. These differences may be helpful to conservation practices facilitating the survival of threatened R. draytonii.

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