My students and I study the behavior of dogs at the Tompkins County SPCA, Cortland Community SPCA, and Chemung SPCA. Our current focus is scent-marking behavior during walks of individual dogs, and how this behavior varies with respect to sex, age, body size, and reproductive condition (intact versus spayed or neutered). We also examine how number of observers, time spent at the shelter, and familiarity with observers affect behavior during walks. Finally, we assess whether individual variation in marking behavior of intact males can be explained by individual variation in levels of testosterone. This study system gives students experience observing, scoring, and analyzing behaviors; there also is opportunity to design independent projects related to shelter animals. Another goal of this long-term study is to engage students in community outreach. Finally, our research provides shelter dogs with additional opportunities for exercise and socialization, as well as chances to display species-typical behaviors. Our results provide context for problematic marking behaviors in the home.