The hypothesis is a core element of science. However, the concept is multifaceted; we address the need to understand the full range of perspectives toward “hypothesis” so that the concept may be applied most usefully in wildlife science. “Hypothesis” has multiple meanings ranging from any speculative thought, to imaginary entities that explain phenomena, to concrete, specific conjectures on the process(es) that lead to an outcome. The latter conjectures are called working or research hypotheses and are the backbone of hypothetico-deductive science. More than conjectures on the existence of a pattern (“existential hypotheses”; e.g., latitudinal effects on clutch size), research hypotheses are conjectures on why the pattern exists. The research hypothesis has gone from nearly nonexistent in the wildlife research literature of the 1970s and 1980s to a prevalence of about 25% in the 1990s and 2000s. We provide several examples of research hypotheses and deductions derived therefrom as formulated by members of the wildlife research community. Although we advocate the use of research hypotheses, we also argue that studies of management treatment effects (magnitude of effect germane, research hypothesis passé) and simple descriptive studies (research hypothesis unnecessary) still have an important place in wildlife science.