Otter populations are in decline globally due to habitat loss, poaching, and water pollution. Of the world’s 13 otter species, nine are listed as endangered or vulnerable to extinction. In addition, North American and Brazilian captive otter populations are not breeding reliably in captivity. For the Otter Conservation Project, CREW scientists are assessing endocrine and seminal characteristics of otters to increase our knowledge of their reproductive biology and establish a database of species-specific norms. Five otter species (North American river otter, Asian small-clawed otter, spotted-necked otter, neotropical otter, and giant otter) housed in North American and/or Brazilian zoological institutions are being monitored non-invasively for fecal hormone metabolites using enzyme immunoassays (EIA). In addition, effective protocols for semen collection and cryopreservation also are being developed. This information will be useful for evaluating individual reproductive status, improving breeding management, and developing assisted reproductive technologies. Ultimately, this improved understanding of otter reproductive biology will benefit both ex situ and in situ conservation efforts of these imperiled aquatic carnivores.