Glucocorticoid hormones in blood are frequently measured as indicators of vertebrate stress response. Sea otters (Enhydra lutris), common in zoos and aquariums, have been documented to secrete both cortisol and corticosterone from adrenal glands. Animals under human care allow for longitudinal study, and non-invasive collection of samples are a priority to the Seattle Aquarium. Glucocorticoid hormones are secreted, metabolized, and excreted in feces. Fecal samples can be collected opportunistically without contaminating the sample with a stress response from handling or taking blood. These samples are often coupled with extensive environmental and medical health notes, which can retrospectively link peaks with major events. The goal of this study was to determine baseline levels for individual sea otters of both sexes and a variety of ages. At the Seattle Aquarium, hormone metabolite groups were measured using commercially available ELISA kits, and validation was achieved by parallelism and accuracy tests. The aquarium has a multiyear dataset of fecal glucocorticoid metabolites for captive sea otters and there was high variation between individuals. Total overall, baseline and peak levels varied over time for each animal. Female otters baseline cortisol levels ranged from 30 - 66 ng/gr dry weight (dw), while corticosterone levels ranged from 45 – 71 ng/gr dw. Male otter baseline cortisol levels ranged from 33 – 59 ng/gr dw, while corticosterone levels ranged from 30 – 41 ng/gr dw. Differences between animals indicate individual responses to stimuli and peaks above baseline for each animal indicate specific adrenal responses. These values can provide insight for husbandry and welfare of these marine mammals as baseline levels are unknown for this species and sample type
