Two young otters died Thursday at the Smithsonian's National Zoo, and officials believe they passed after ingesting dye used on their fur for identification purposes.
The Zoo said the young adult Asian small-clawed otters were among seven that received routine quarantine exams, during which they received contraceptive implants. Officials said that they were reintroduced to the 13-member family and appeared to be eating and acting normally.
However, later that afternoon keepers said they noticed that two of the otters showed discomfort while moving and were taken to the Zoo's hospital for treatment. They later died.
The Zoo said a preliminary necropsy suggested that the otters had methemoglobinemia, a condition affecting oxygen transport by the blood, which caused liver and kidney failure.
The Zoo said in a release that the most likely cause of death is ingestion of the dye.
More from the Zoo's release:
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.
Zoo officials said the excess dye was cleaned off the other otters, and all 11 remaining otters appear to be acting normally. They will remain in quarantine.
The Zoo said it has ceased using the dye.