We are very saddened by the passing of Casey the Leopard Seal.Casey’s health and condition had been deteriorating over a lengthy period of time despite intensive veterinary treatment and care.Although every effort was made by both Taronga’s Marine Mammal and veterinary teams, Casey’s health had shown no acceptable sign of improvement and staff made the heart-breaking decision to put Casey to sleep on Friday.Casey arrived at Taronga in 2007, after being found washed ashore at Wattamolla south of Sydney in poor health and with a fresh cookie-cutter shark wound to his abdomen.From the Antarctic, Casey was unable to be returned to the wild in case he transferred any unknown diseases to the fragile wild population. Nursed back to health, he found a home at Taronga's Great Southern Oceans where he fast became one of our most popular residents with keepers and visitors alike.Leopard Seals are not found in zoos anywhere else in the world, so working with and learning from Casey was a unique opportunity for our Marine Mammal team. Casey also assisted with research by the Australian Marine Mammals Research Centre (AMMRC) to study Leopard Seals, helping the species into the future.Taronga’s Marine Mammal team would like to thank everyone involved in Casey’s management and care over the past few months, particularly our vets.We hope that Casey’s interactions with our staff and visitors contributed to an awareness of conservation and appreciation of this amazing Antarctic species.