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During the reproductive season, sea turtles use a restricted area in the vicinity of their nesting beaches, making them vulnerable to predation. At Raine Island (Australia), the highest density green turtle Chelonia mydas rookery in the world, tiger sharks Galeocerdo cuvier have been observed to feed on green turtles, and it has been suggested that they may specialise on such air-breathing prey. However there is little information with which to examine this hypothesis. We compared the spatial and temporal components of movement behaviour of these two potentially interacting species in order to provide insight into the predator-prey relationship. Specifically, we tested the hypothesis that tiger shark movements are more concentrated at Raine Island during the green turtle nesting season than outside the turtle nesting season when turtles are not concentrated at Raine Island. Turtles showed area-restricted search behaviour around Raine Island for ~3–4 months during the nesting period (November–February). This was followed by direct movement (transit) to putative foraging grounds mostly in the Torres Straight where they switched to area-restricted search mode again, and remained resident for the remainder of the deployment (53–304 days). In contrast, tiger sharks displayed high spatial and temporal variation in movement behaviour which was not closely linked to the movement behaviour of green turtles or recognised turtle foraging grounds. On average, tiger sharks were concentrated around Raine Island throughout the year. While information on diet is required to determine whether tiger sharks are turtle specialists our results support the hypothesis that they target this predictable and plentiful prey during turtle nesting season, but they might not focus on this less predictable food source outside the nesting season.

Item Type:	Refereed Article
Keywords:	animal behavior, article, chelonia mydas, diet, feeding behavior, food availability, foraging, Galeocerdo cuvier, nesting, nonhuman, predator prey interaction, seasonal variation, shark, species translocation, turtle
Research Division:	Agricultural, Veterinary and Food Sciences
Research Group:	Fisheries sciences
Research Field:	Fisheries sciences not elsewhere classified
Objective Division:	Animal Production and Animal Primary Products
Objective Group:	Fisheries - wild caught
Objective Field:	Fisheries - wild caught not elsewhere classified
UTAS Author:	Barnett, A (Dr Adam Barnett)
ID Code:	81753
Year Published:	2012
Web of Science® Times Cited:	52
Deposited By:	Sustainable Marine Research Collaboration
Deposited On:	2013-01-07
Last Modified:	2013-05-07
Downloads:	649 View Download Statistics