Some Observations and Hypothesis on Minimal Forage Syndrome ( MFS) for Green and Hawksbill Turtles South of the Thirtieth Parallel
Recently four turtles (3 green and 1 hawksbill) have arrived on the far south coast of NSW displaying very similar symptoms. All were found in upper estuaries around oyster leases and in very shallow water “sunning “ themselves.
The intercostal space between shell scutes is widened.
The dark connecting material in these widened spaces is spongy grey in colour and flaky.
The animal is flaccid lacking energy.
The body position is limp and lethargic.
The flippers are coated with patches of what appears to be a fungal crust.
The outer layers of scute material is flaking and splitting.
The shell margins appear shrunken to the extent that the joints appear to have had pieces evulsed.
This appears as extra serrations around the shell margins.
Body weight appears low.
Animals appear to be in the 9 to 12 kilograms weight.
One animal had a five mm coating of sand and algae over the shell and front flippers.
One animal had brown enteromorpha growing on the left side of the shell and was floating.
Female hawksbill photo ABCHawksbill turtle photo Dave Harasti
First Approach…” The Green” regime
The animals are rehydrated, given antibiotics, placed on a drip and slowly force-fed a suitable “mush” of chopped up codium, ulva and squid. They eventually accept food offered in the water.
They are kept in a shallow warmed pool…. 24 degrees and pool water is changed regularly.
They are be moved to a suitable tank and are retained until the sea water temperature rises in summer.
A Possible Scenario
The animals leave their area of hatching and cross the Pacific during their first 8 to 10 years . On return from the eastern Pacific they forage by following warm water currents south leaving behind their normal forage fields. They enter waters containing forage material that they do not recognise as useful. Their bodies begin to draw down on condition and bone resources. They enter estuaries where the water is shallow and warmer than the open ocean. Here they crop green enteromorpha , ulva and codium in sufficient quantities to just maintain life but not enough to replace the wasting effect. The water temperature by now is sufficiently low (17 deg) to shut down their reptilian body metabolism adding still further to the animals inability to extract necessary minerals and protein from the meagre food gathered. The end result of this group of abiotic and biotic factors can be death.
The Galapagos Evidence
From studies conducted on tortoise species in the Galapagos the evidence is clear that diet plays a major role in shell appearance and condition. Overfed animals develop gross shells while underfed animals show considerable morphing of shell shape and size. This appears one of the evolutionary engines for change in land tortoises.
The Fish Evidence
Since 1987 tropical fish eggs and larval forms of fish have been located in the area from Bermagui to Eden. These intrusions are known to ride the Eastern Australian Current from north of Bundaberg coming in pulses over the late summer months ..Dec. to March…to be hatched on Heron Island and to end up in Eden. This is the result of pulses of warm Eastern Australian Current water following a natural summer pattern and not really unusual. These currents provide an abiotic engine suitable for young turtles to ride.
Earlier this year a slightly smaller green turtle arrived in care in Merimbula .The dorsal shell section and the dorsal surfaces of both the proximal and distal flippers had a thick coating of fine estuary sand and filamentous algae. ( This was referred to earlier. )When removed, this coating weighed one third of the turtles clean weight.
This animal did not sur vive despite immediate care.
We believe the drag of this extra weight was a factor in the animal’s demise.
The Border Issue
From turtle tagging programs conducted on Heron Island and at Mon Repos by Col Limpus it is clear that these marine reptiles travel great distances from their place of birth. This has the potential to transport unwanted diseases into local areas and change the gene pool. Mostly their travels are northward and eastward but now some are venturing south. I would suggest that this southward travel is not a new phenomenon but has been operational for many years. We just have not had the evidence. Returning the animals to 24 degree water gives them an opportunity to resume tropical life and go on to reproduce.
The Anthropomorphic Response
Marine reptiles need all the help we humans can offer. Please pass on your comments, information treatment protocols or any other known experiences that might help carers in their effort to learn how they may help animals in distress. Please add or subtract from these comments. Feel free to scribble over this paper and return it. Only by shared information will our efforts produce the best results.