In this introductory paper we describe the 10 papers that compose this Special Feature Theoretical and analytical advances in mammalian isotope ecology. This Special Feature contains 6 review-style papers, written by some of the leaders in the field. These are followed by 4 data-driven articles. The review-style papers were presented at a symposium we organized during the 90th annual meeting of the American Society of Mammalogists. The symposium was dedicated to Donald M. Schell (1940–2009), who pioneered research in isotopic ecology.