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Passive Prey Discrimination in Surface Predatory Behaviour of Bait-Attracted White Sharks from Gansbaai, South Africa. Animals (Basel) 2021; 11:ani11092583. [PMID: 34573551 PMCID: PMC8471732 DOI: 10.3390/ani11092583] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2021] [Revised: 09/01/2021] [Accepted: 09/01/2021] [Indexed: 11/26/2022] Open
Abstract
Simple Summary White sharks, in surface passive prey predatory behaviour, are initially attracted by the olfactory trace determined by the bait and then implement their predatory choices to energetical richer prey, especially thanks to their visual ability, which plays an important role in adults and immatures with dietary shifts in their feeding patterns. Gansbaai represents a hunting training area for white sharks who are changing their diet. Abstract Between the years 2008 and 2013, six annual research expeditions were carried out at Dyer Island (Gansbaai, South Africa) to study the surface behaviour of white sharks in the presence of two passive prey: tuna bait and a seal-shaped decoy. Sightings were performed from a commercial cage-diving boat over 247 h; 250 different white sharks, with a mean total length (TL) of 308 cm, were observed. Of these, 166 performed at least one or more interactions, for a total of 240 interactions with bait and the seal-shaped decoy. In Gansbaai, there is a population of transient white sharks consisting mainly of immature specimens throughout the year. Both mature and immature sharks preferred to prey on the seal-shaped decoy, probably due to the dietary shift that occurs in white sharks whose TL varies between 200 cm and 340 cm. As it is widely confirmed that white sharks change their diet from a predominantly piscivorous juvenile diet to a mature marine mammalian diet, it is possible that Gansbaai may be a hunting training area and that sharks show a discriminate food choice, a strategy that was adopted by the majority of specimens thanks to their ability to visualize energetically richer prey, after having been attracted by the odorous source represented by the tuna bait.
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Jiang DY, Motani R, Tintori A, Rieppel O, Ji C, Zhou M, Wang X, Lu H, Li ZG. Evidence Supporting Predation of 4-m Marine Reptile by Triassic Megapredator. iScience 2020; 23:101347. [PMID: 32822565 PMCID: PMC7520894 DOI: 10.1016/j.isci.2020.101347] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Revised: 06/09/2020] [Accepted: 07/04/2020] [Indexed: 11/28/2022] Open
Abstract
Air-breathing marine predators have been essential components of the marine ecosystem since the Triassic. Many of them are considered the apex predators but without direct evidence-dietary inferences are usually based on circumstantial evidence, such as tooth shape. Here we report a fossil that likely represents the oldest evidence for predation on megafauna, i.e., animals equal to or larger than humans, by marine tetrapods-a thalattosaur (∼4 m in total length) in the stomach of a Middle Triassic ichthyosaur (∼5 m). The predator has grasping teeth yet swallowed the body trunk of the prey in one to several pieces. There were many more Mesozoic marine reptiles with similar grasping teeth, so megafaunal predation was likely more widespread than presently conceived. Megafaunal predation probably started nearly simultaneously in multiple lineages of marine reptiles in the Illyrian (about 242-243 million years ago).
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Affiliation(s)
- Da-Yong Jiang
- Laboratory of Orogenic Belt and Crustal Evolution, Ministry of Education; Department of Geology and Geological Museum, School of Earth and Space Sciences, Peking University, Yiheyuan Street. 5, Beijing 100871, People's Republic of China
| | - Ryosuke Motani
- Department of Earth and Planetary Sciences, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA
| | - Andrea Tintori
- Dipartimento di Scienze della Terra, Università degli Studi di Milano, Via Mangiagalli, 34-20133 Milano, Italy
| | - Olivier Rieppel
- Integrative Research Center, The Field Museum, Chicago, IL 60605-2496, USA
| | - Cheng Ji
- Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Beijing East Road 39, Nanjing, Jiangsu 210008, People's Republic of China
| | - Min Zhou
- Laboratory of Orogenic Belt and Crustal Evolution, Ministry of Education; Department of Geology and Geological Museum, School of Earth and Space Sciences, Peking University, Yiheyuan Street. 5, Beijing 100871, People's Republic of China
| | - Xue Wang
- Laboratory of Orogenic Belt and Crustal Evolution, Ministry of Education; Department of Geology and Geological Museum, School of Earth and Space Sciences, Peking University, Yiheyuan Street. 5, Beijing 100871, People's Republic of China
| | - Hao Lu
- Laboratory of Orogenic Belt and Crustal Evolution, Ministry of Education; Department of Geology and Geological Museum, School of Earth and Space Sciences, Peking University, Yiheyuan Street. 5, Beijing 100871, People's Republic of China
| | - Zhi-Guang Li
- The Geoscience Museum, Hebei GEO University, No. 136 East Huai'an Road, Shijiazhuang, Hebei 050031, People's Republic of China
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