Two young adult Asian small-clawed otters, from a new family of 13, died late yesterday at the Smithsonian's National Zoo. Seven otters received routine quarantine exams during which the animals had patches of their fur dyed for identification purposes and they received contraceptive implants. After the procedures, all animals were reintroduced to the family group and appeared to be eating and acting normally.
Later in the afternoon, keepers noticed that a female and male showed discomfort while moving around. They were immediately transported to the Zoo's hospital for treatment, but unfortunately both otters died. Examination and preliminary necropsy results suggest that the animals had methemoglobinemia, a condition affecting oxygen transport by the blood, which caused liver and kidney failure.
The most likely cause of death is ingestion of the dye. This dye has been routinely used by wildlife researchers and professionals on birds, marine mammals, small mammals and ungulates among many others. The National Zoo has used the product for more than three decades on numerous species without incident, including golden lion tamarins, prairie dogs, black-footed ferrets and the previous group of otters that lived on Asia Trail. The excess dye was cleaned off the other otters. All 11 otters appear to be acting normally today. They remain in quarantine under close observation by their keepers and veterinary staff. The National Zoo has ceased using the dye.