We describe activity patterns of North American River Otters (Lontra canadensis) in relation to social group size and the presence of young. Over the course of 15 y, we collected observations of 8 River Otter behaviors from a network of citizen scientists in northern California, retaining 1692 records following a rigorous data-cleaning process. Observers were asked to indicate 1 or more of the following 8 behaviors: “diving”, “swimming”, “walking”, “running”, “digging”, “turning rocks”, “pursued birds”, and “retreating from observer.” We treated “digging”, “turning rocks”, and “pursued birds” as alternative foraging strategies in some comparisons. Assessment of these reports showed that families were seen diving, running, and retreating from the observers more frequently than adult groups. Likewise, adult social groups behaved differently than solitary adult otters. Propensity to retreat from humans increased with increasing group size in social otters, whereas diving behavior also increased with group size. Solitary adults employed alternative foraging strategies more than adults in social groups. Citizen observers also reported that diving and styles of foraging behavior varied among months for adult otters. Taken together, these results provide evidence that citizen-science questionnaires can be used to provide insight into the natural behaviors of species that are difficult to observe.