Simple SummaryAnimals in human care, such as northern sea otters (Enhydra lutris kenyoni), allow for long-term studies of the stress response to environmental stimuli, husbandry, and medical procedures. The goal of this study was to analytically validate the use of two commercially available enzyme immunoassay kits to measure fecal glucocorticoid metabolites (FGMs), specifically cortisol-immunoreactive and corticosterone-immunoreactive metabolites. Individual baseline levels of four adult sea otters were calculated, each of which were found to be unique. We attempted to match FGM peaks with caregiver notes on environmental enrichment, husbandry changes, and medical procedures. This work provides insight into effective husbandry management to improve the welfare of sea otters and other marine mammals under human care.AbstractFecal glucocorticoid metabolites (FGMs) have been used as a non-invasive and indirect measurement of the complex stress response in a variety of species. Animals in facilities under managed care allow for the longitudinal study of FGMs in a controlled environment. Animal histories often include environmental, husbandry, and medical notes that can be matched to FGM concentrations to aid in the physiological validation of adrenal stimulation and response. The goal of this study was to demonstrate analytical validations using two enzyme-linked immunosorbent assays (EIA) to measure FGMs from northern sea otters (Enhydra lutris kenyoni) under human care (Seattle Aquarium, Seattle, WA, USA) and to determine baseline and stress response spike levels for individual sea otters. Individual variation was found among the four subjects in the study with fecal baseline levels ranging from 20.2 to 83.7 ng/g for cortisol-immunoreactive metabolites and 52.3 to 102 ng/g for corticosterone-immunoreactive metabolites. As a retrospective study, 39 percent of hormone peaks were associated with notes and most FGM spikes were associated with veterinary procedures or days in which enrichment items were provided and produced an excitatory response. Monitoring baseline FGMs levels and events associated with hormone peak values may provide insight into effective husbandry management to improve the overall welfare of sea otters and other marine mammals.