In this dissertation I argue that, in the field of conservation, the boundary separating science from advocacy appears to be undergoing a shift as the number of research scientists at conservation advocacy organizations grows. Drawing on data from interviews with scientists at a prominent conservation non-governmental organization (NGO), I identify and analyze the kinds of rhetorical work NGO scientists engage in as they attempt to participate effectively in the forums of both science and advocacy. I also analyze the publications of one scientist at the same organization to identify features of the discourse of NGO conservation science that suggest a shift---or at least a blurring---of the boundary between science and advocacy in conservation. My discourse analysis focuses on publications from forums of scholarship and advocacy including, as a representation of discourse in the latter forum, an example of gray literature. Gray literature refers to reports, books, and other texts produced and distributed outside the channels of the academic and publishing industry. The study highlights the types of "boundary work" NGO scientists are engaged in to establish their membership in the scientific community as well as specific features typical of their rhetoric that result from their occupying a "hybridized" cultural and professional space where science and advocacy overlap.