Shape Discrimination and Visual Predatory Tactics in White Sharks

Strong, Wesley R.

doi:10.1016/b978-012415031-7/50022-7

Cited by 48 publications

(65 citation statements)

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“…The surface appears to be the most dangerous location within the water column for airbreathing animals that are attacked by sharks, and green turtles may dive in a manner to minimize risk while surfacing (e.g. Strong 1996, Glen et al 2001, Heithaus & Frid 2003, Heithaus 2004. Loggerhead turtles were seen at the surface more often than green turtles, suggesting more time spent at the surface and thus greater susceptibility to sharks.…”

Section: Discussionmentioning

confidence: 96%

Biology of sea turtles under risk from tiger sharks at a foraging ground

Heithaus

Frid²,

Wirsing³

et al. 2005

Mar. Ecol. Prog. Ser.

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It is important to understand the population structure and space use of sea turtles because of their potential effects on the dynamics of nearshore ecosystems. Much of our current understanding is skewed because the ecology of sea turtles on their foraging grounds is known best from areas where there are, or have been, major human impacts. We studied green Chelonia mydas and loggerhead Caretta caretta sea turtles on the relatively pristine feeding ground of Shark Bay, Western Australia, where tiger sharks Galeocerdo cuvier are a major mortality agent. Recapture rates were lower for green than for loggerhead turtles, possibly reflecting a larger population rather than low site fidelity for greens. The sex ratio of loggerhead turtles was not significantly different from 1:1, whereas green turtles showed a strong female bias. Size distributions of both species were skewed towards larger (and presumably older) individuals relative to a human-impacted feeding ground in eastern Australia. Body condition varied temporally for green turtles, but not for loggerhead turtles, possibly due to longer distances traveled to nesting beaches by green turtles. Rates of shark-inflicted injuries were higher for loggerhead turtles, especially males, than for greens. Sublethal effects of these injuries were not evident. There are notable differences between sea turtles threatened primarily by tiger sharks in Shark Bay and populations on feeding grounds where historical and current mortality causes are anthropogenic. We conclude that without baseline data from relatively pristine habitats our understanding of human impacts on sea turtle populations suffers from a limited scope.

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Section: Discussionmentioning

confidence: 96%

Biology of sea turtles under risk from tiger sharks at a foraging ground

Heithaus

Frid²,

Wirsing³

et al. 2005

Mar. Ecol. Prog. Ser.

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“…While crepuscular and nocturnal feeding behaviour is known in many species of large predatory sharks (Klimley et al 1992), they are also known to be opportunistic and inquisitive and have been observed to investigate opportunities to feed day and night (Wetherbee 1990;Strong 1996). The small number of incidents analysed for patterns of attack (Fig.…”

Section: Environmental Influences On Shark Attacksmentioning

confidence: 99%

Changing patterns of shark attacks in Australian waters

West¹

2011

Mar. Freshwater Res.

122

125

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Abstract. Although infrequent, shark attacks attract a high level of public and media interest, and often have serious consequences for those attacked. Data from the Australian Shark Attack File were examined to determine trends in unprovoked shark attacks since 1900, particularly over the past two decades. The way people use the ocean has changed over time. The rise in Australian shark attacks, from an average of 6.5 incidents per year in 1990-2000, to 15 incidents per year over the past decade, coincides with an increasing human population, more people visiting beaches, a rise in the popularity of water-based fitness and recreational activities and people accessing previously isolated coastal areas. There is no evidence of increasing shark numbers that would influence the rise of attacks in Australian waters. The risk of a fatality from shark attack in Australia remains low, with an average of 1.1 fatalities year À1 over the past 20 years. The increase in shark attacks over the past two decades is consistent with international statistics of shark attacks increasing annually because of the greater numbers of people in the water.

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“…comm., cf. Strong 1996), with the tiger shark Galeocerdo cuvier being the only predator that is specialised to take large cheloniid turtles (Witzell 1987). The generally low metabolism of cold-blooded animals such as reptiles probably contributes to the longevity of these animals (Jonsson 1991).…”

Section: Effects Of Temperature Changesmentioning

confidence: 99%

Cold-blooded divers: temperature-dependent dive performance in the wild hawksbill turtle Eretmochelys imbricata

Storch

Wilson²,

Hillis-Starr³

et al. 2005

Mar. Ecol. Prog. Ser.

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Sea turtles are diving ectotherms that are influenced by the temperature of the ambient water, although swimming activity can temper this influence via increased body temperatures enhanced by the thermal inertia of these large animals. We successfully equipped 3 nesting hawksbill turtles Eretmochelys imbricata with time-depth recorders (TDRs) to monitor water temperature and dive depth over the duration of the re-migration interval between 2 successive nesting seasons. Data sets for up to 22 mo were obtained, showing fluctuations in water temperature over the seasons. Nocturnal dive behaviour of the turtles at their foraging grounds revealed an increase in dive duration with decreasing water temperatures in winter. A model is provided to estimate dive duration for the range of temperatures experienced by this species in the wild. The data on vertical velocity during ascent and descent phases as a parameter for activity failed to show thermal dependence. It is concluded that changes in water temperature have an effect on the behavioural ecology of hawksbill turtles.

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Shape Discrimination and Visual Predatory Tactics in White Sharks

Cited by 48 publications

References 0 publications

Biology of sea turtles under risk from tiger sharks at a foraging ground

Biology of sea turtles under risk from tiger sharks at a foraging ground

Changing patterns of shark attacks in Australian waters

Cold-blooded divers: temperature-dependent dive performance in the wild hawksbill turtle Eretmochelys imbricata

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