Morbidity and mortality of Asian small-clawed otters ( <i>Aonyx cinereus</i> ) and North American river otters ( <i>Lontra canadensis</i> ) in US zoos and aquaria from 2000 to 2020: A survey of lesions in 2 popular otter species

Asian small-clawed otters (<i>Aonyx cinereus</i>, ASCOs) and North American river otters (<i>Lontra canadensis</i>, NAROs) are commonly housed at zoos and aquaria in the United States. The few reports of diseases in these species have mainly focused on free-ranging populations and do not represent otters in managed care. Necropsy reports from 93 individuals, 71 ASCO and 22 NARO, that died or were euthanized between 2000 and 2020 from 10 separate institutions were evaluated, including 47 females, 45 males, and 1 unreported sex. All otters with known ages ranged between 2 months and 21 years of age (median = 14 years). Otters were further divided into age classes according to known lifespan. ASCO age classes were juvenile (4; 6%), adult (26; 37%), older adult (9; 13%), and geriatric (32; 45%). NARO age classes were juveniles (0; 0%), adult (5; 23%), older adult (5; 23%), and geriatric (12; 55%). Common causes of death or euthanasia in both species included malignant neoplasia (29), chronic renal disease and/or urolithiasis (27), degenerative joint disease (13), and cardiovascular disease (10). Severe gastrointestinal hemorrhage caused mortality in 9 (13%) ASCOs. Common morbidities or comorbidities included periodontal disease (30) and degenerative joint disease (21). Consistent health and disease surveillance of these otter species in managed care will further elucidate mechanisms of disease, aid in the development of preventative and therapeutic strategies, and continue optimizing standards of care.