Oral Sedation in Open Water to Facilitate Recovery and Care of a Critically Injured Indo-Pacific Humpback Dolphin (Sousa chinensis)
Paolo R. Martelli1; Sarah M. Churgin1*; Nimal Fernando2; Grant Abel1; Gary Wong1; Foo Khong Lee1
A severely injured free-living, adult male Indo-Pacific humpback dolphin (Sousa chinensis) was discovered in the waters off northern Lantau Island in the Hong Kong Special Administrative Region. The animal had at least four identifiable injuries, the worst being a deep laceration through the peduncle anterior to the insertion of the flukes with suspected underlying fracture of the vertebral column. Its injuries were consistent with a strike by a small outboard motor boat propeller. Although the animal was weak, it evaded capture with hoop nets and other capture devices for three weeks. During this time, it was seen foraging from by-catch of gillnet fishing vessels in the area and began to willingly take fish thrown to it by personnel aboard. Taking advantage of this behavior, oral sedation was administered in fish purchased from local gillnet operators using diazepam (80 mg, 0.6 mg/kg) and butorphanol (50 mg, 0.37 mg/kg). A suitable level of sedation to allow handling was achieved after about three hours, and the animal was safely caught using a break away hoop-net. Once restrained in the net, it was then guided into a sling and transported to Ocean Park for care. Examination confirmed that the most severe wound over the peduncle extended down to the vertebral column, but blood supply to the flukes remained intact. Further stabilization and treatments were instituted. Although the animal's wounds and general condition improved initially, it rapidly deteriorated after 72 hours and was humanely euthanized four days after rescue. A post-mortem CT scan confirmed multiple vertebral fractures and associated osteomyelitis. This is the first known report of successful oral sedation of a small odontocete cetacean in open water for purposes of recovery and transport. Previous reports have described parenteral sedation at sea to facilitate disentanglement of North Atlantic right whales.1,2
* Presenting author
1. Moore M, Walsh M, Bailey J, Brunson D, Gulland F, Landry S, Mattila D, Mayo C, Slay C, Smith J, Rowles T. Sedation at sea of entangled North Atlantic right whales (Eubalaena glacialis) to enhance disentanglement. PLoS One. 2010;5(3):e9597.
2. Brunson DB, Rowles TK, Gulland F, Walsh M, Dunn JL, Hammer T, Moore M. Techniques for drug delivery and sedation of a free-ranging North Atlantic right whale (Balaena glacialis). In: Proceedings from the American Association of Zoo Veterinarians. Milwaukee, WI; 2002:320–322.