Guadalupe fur seal alopecia: a metabolic syndrome associated to climatic anomalies?

Alopecia is characterized by the thinning and loss of hair or fur, and has been observed in different marine carnivores. Until recently, there were no records of alopecia in marine mammals from the Northeast Pacific Ocean. However, sightings of juvenile male Guadalupe fur seals with patchy alopecia in the ventral body have been reported in the San Benito Archipelago. This is concerning given that the species is considered endangered under Mexican law and has only started to recover from near extinction less than a century ago. We captured 13 fur seals at San Benito Archipelago during the summer of 2017 and 2018 and collected fur samples for common dermatological analysis, as well as scanning electron microscopy and X-ray spectroscopy. We found marked damage to the structure of guard fur, with loss of integrity, medullary damage and perforations. Damage to secondary underfur hair was less common. We found no evidence of dermatophyte microorganisms or ectoparasites commonly associated with alopecia. We suggest that the damage is caused by metabolic alterations secondary to nutritional stress that is consequential to high sea surface temperatures that alter prey availability. This is the first study of alopecia in an otariid pinniped of the Northeast Pacific Ocean. ### Competing Interest Statement The authors have declared no competing interest.