and want to continue in order to develop a better 

 model. We believe we are working with two major 

 sub-populations, and though there was increased 

 nesting in 1986, we believe this to be a result of 

 natural fluctuations. We tag with monel and 

 plastic, and have received returns from the Sea of 

 Cortez, as well as many from Costa Rica. Clutch 

 size is 60-69. Studies show that the pivotal 

 temperature for sex determination is 31° C, less 

 than 27° C during the 2nd third of incubation 

 produces all males, and over 31°C produces all 

 females. 



LIMPUS ; Chelonia depressa is now known as Natator 



depressa ; The flatback is no longer a green 

 turtle. This change is based on electrophoretic 

 studies and skeletal features. The flatback has 

 greater affinities with Lepidochelys . 



It possesses 2 prefrontals (like hawksbills) , but 

 one pre-ocular scale not found in other species. 

 It is carnivorous and eats sea pens, soft corals 

 and crustaceans. The hatchlings are large and 

 have a disruptive color and shape with white 

 borders on the flippers. They weigh approximately 

 40 gms. The carapace edges are upturned. Their 

 skin is very similar to Dermochelys . 



Flatbacks are known to nest only in Australia, but 

 sub-adults do migrate and have been captured in 

 Indonesian waters. Major nesting beaches are 

 limited. Crab Island is a 5 km sand island with 

 2,000 nesting turtles/year which peak in August 

 and September. Peak Island has 400-500 

 turtles/year, and it is a preservation zone with a 

 length of 500 meters. Wild Duck Island National 

 Park also has 400-500 turtles/year. 



Crab Island is an aboriginal reserve where 

 harvesting takes place. There are a few other 

 major nesting sites, as well, and they nest 

 sporadically on all the beaches of northern 

 Australia in small numbers. They nest both day 

 and night. Hatchling predation is low (less than 

 2% to crabs, and 0.2% to birds, though nocturnal 

 birds take 3 0% at Crab Island) . 



Flatbacks are found in inshore waters where there 

 is a muddy bottom. This coincides exactly with 

 the areas where shrimp are fished. Australian 

 shrimpers do not tow long, however, thus mortality 



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