Taronga Zoo euthanises sick leopard seal

Taronga Zoo has had to euthanise the world's only captive leopard seal after it fell ill.

Casey, a seven year-old seal stopped eating at the start of the year and zookeepers observed him going "off colour" and deteriorating.

Explaining the move, Taronga Zoo Media Relations Manager Mark Williams told the Sydney Morning Herald "you can't force feed an animal."

Casey was put down in late February after zoo vets, keepers and curators assessed his condition and decided he had no chance of recovery.

Williams added "he was a very popular animal with staff and visitors but his well-being was more important."

Casey was found by NSW Parks and Wildlife staff washed up at Wattamolla Beach in the Royal National Park in 2007.

The animal, whose natural habitat is in Antarctic waters, had a fresh cookie-cutter shark bite to his abdomen.

Zoo staff estimated he was one year old at the time.

An international environmental agreement prevented Casey from being returned to Antarctica in case he transferred diseases into the fragile southern environment and he was taken to Taronga Zoo for care.

Casey was put down only a few days after a Danish zoo sparked international headlines when it killed an 18-month-old giraffe called Marius and butchered it in front of children before feeding it to the zoo's lions.

Whereas Marius was put down to prevent inbreeding, Casey was euthanised for poor health, although Taronga Zoo did not know why the seal was sick.

Leopard seals have a lifespan of about 12 years.

Casey's carcass was disposed of under Taronga's environmental waste procedures.