We developed and field-tested an active learning exercise designed to provide biology students with the opportunity to consider key aspects of the nature of science as a method of inquiry, particularly the roles of observation and inference in the development of scientific explanations and how scientists deal with uncertainty. In the activity students assume the role of a wildlife biologist, using available evidence to best explain the cause of the decline of a rabbit population in a state park. Using a guided-inquiry approach, students are provided evidence in a sequential fashion. After each bit of evidence is provided, they form inferences and either retain their initial explanation or reject it. Results of the field testing suggest that the activity may positively impact students' perceived understanding of important aspects of the nature of science, and their comfort level in dealing with uncertainty. The investigative, observation/inference-based model utilized shows promise in making the nature of science an organizing theme for the course.