Saturday, 27 February 2016

Leatherback Turtle near Cairns

I get cheeky and go out to the Great Barrier Reef in my open boat on calm days.  Today, I was in deep dark blue waters about 5 km from the reef when I passed by a giant turtle basking just below the surface.  It did not seem to be worried by a 40 horsepower outboard passing by at full throttle only 20 m away.  However when I turned and can back for a closer look the turtle lifted its head up for a look, saw me and departed to the depths.  I don't think there was anything wrong with the turtle.
Leatherback Turtle near Green Island-Cairns North Queensland

The special thing is that there are no published records that I can find for leatherback turtles (Dermochelys coriacea) near Cairns.  The nearest record in the Atlas of Living Australia is from Mackay and dates from 1985.  Another record shows on the map near Cooktown, however this record is for a fossil!  Leatherback turtles are endangered, so this sighting is significant.

The water was clear and there were some small clumps of floating yellow-brown algae, probably sargassum and occasional lines of widely dispersed mangrove detritus.  However there were no major collections of floating materials which would indicate a downwelling zone and there was no other wildlife activity in the area.  In the water, transparent jellyfish with fine filaments at the edge of the bell were visible (Aurelia?) on the reef.  I even photographed one strange jellyfish then realized that the bell had been eaten by something, probably a turtle.  Leatherback turtles eat jellyfish as do green turtles.

Checkout the teeth a Leatherback has for dealing with jellyfish in this blog

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