Turtles are a key environmental value and attraction for both tourists and residents in the Lord Howe Island Marine Park (LHIMP). The two most common species are the green turtle (Chelonia mydas) and hawksbill turtle (Eretmochelys imbricata), both of which are listed as Vulnerable in NSW. The leatherback turtle (Dermochelys coriacea) and loggerhead turtle (Caretta caretta) are also occasionally seen in the LHIMP, and are both listed as Endangered in NSW.

Given marine turtles are valuable and threatened species, understanding both local and global threats to their populations is important. Injured and dead turtles are occasionally seen in the LHIMP and these observations can help identify which threats are having the greatest impact on turtles in the marine park.

In order to determine cause of death, turtle carcasses found in the LHIMP were previously transported to Dolphin Marine Rescue in Coffs Harbour for post-mortem examination. Thankfully, local island vet, Dr Courtney Turner and veterinary nurse Deb Thompson have expanded their expertise to include turtle necropsies, so that any found deceased in the marine park can now be examined locally. Last May, Courtney and Deb undertook necropsies on five turtles that had been found dead on beaches in the marine park between May and November in 2021. Four were juvenile green turtles and one was a juvenile hawksbill turtle.

Post-mortem results identified the likely cause of death for all animals, with three dying from severe spirorchiid fluke infection. This infection is a common cause of death in sea turtles globally, and results from exposure to fluke larvae in the wild. The other two turtles examined had most likely died from shark predation, and internal bleeding possibly caused by external trauma such as boat strike.

From the results of these post-mortem examinations, along with other observation of injured turtles, some key threats to turtles in the LHIMP can be identified. Spirorchid fluke infection is the most common cause of death for turtles in the LHIMP, resulting in the death of at least five turtles in the marine park since January 2020. Boat-strike is the next most commonly occurring threat, being a likely cause of death or injury of three turtles in the same period. Two turtles were also observed with injuries from plastic entanglement, but thankfully no turtle deaths were attributed to plastic entanglement or ingestion.

Rare turtle observations

In the last month, there have been two rare turtle observations in the LHIMP. The first was a set of turtle tracks leading up Blinky Beach, with a ‘slide’ mark at the base of the dune, and a set of tracks leading back to the water. Correspondence with staff at Taronga Zoo suggested these tracks may have been made by a Hawksbill turtle, although with the nearest nesting area being far north of LHIMP, its reasons for leaving the water remain unknown.

The second observation was a juvenile green turtle found dead on lagoon beach. With its shell measuring only 9cm long, the turtle was likely between 2 weeks and 2 months old and had probably arrived from a nesting area in the Great Barrier Reef. The difficult journey faced by juvenile turtles was evidenced by the multiple injuries it had sustained before its death.

Thanks to everyone who reports wildlife strandings and observations in the LHIMP, so that marine park staff can continue to record and monitor these occurrences.

This article appeared the The Lord Howe Island Signal, 1 August 2022.