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Azevedo OM, Correia AM, Micarelli P, Reinero FR, Rijllo G, Giglio G, Sperone E. Sex Differences in the Individual Behaviour of Bait-Attracted White Sharks ( Carcharodon carcharias, Linnaeus, 1758) Are Linked to Different Environmental Factors in South Africa. BIOLOGY 2022; 11:biology11121735. [PMID: 36552245 PMCID: PMC9774687 DOI: 10.3390/biology11121735] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/08/2022] [Revised: 11/24/2022] [Accepted: 11/25/2022] [Indexed: 12/05/2022]
Abstract
The white shark (Carcharodon carcharias) is a charismatic species and, consequently, one of the most studied and protected sharks. This species can be found in a wide range of temperatures and depths, showing site fidelity and migrating across the oceans. This offers a challenge to understanding the processes influencing their lifecycle and, more importantly, assessing anthropogenic disturbances to their populations. These predators' behaviour has been linked to diverse abiotic factors. Here, an ethological approach was used to understand the influence of environmental variables on white shark behaviour. A different environmental impact was found between the activity of females and males toward the bait. Females performed a higher number of behaviours under daylight, lower sea surface temperatures, short wavelets, clear and cloudy skies, under La Niña events, elevated moonlight and high tides. Males behaved with more complexity at dawn, medium sea surface temperatures, large wavelets, few clouds, high tides, and elevated moonlight. The world's aquatic habitats are experiencing significant physiochemical shifts due to human-induced climate change. Knowledge about how white sharks respond to environmental factors is essential to guide management and conservation actions.
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Affiliation(s)
- Olga Mouteira Azevedo
- Department of Biology, Ecology and Earth Sciences (DiBEST), University of Calabria, 87036 Rende, Italy
- Correspondence: (O.M.A.); (E.S.)
| | - Ana Mafalda Correia
- Coastal Biodiversity Laboratory, Interdisciplinary Centre of Marine and Environmental Research (CIIMAR), 4450-208 Matosinhos, Portugal
- Department of Biology, Faculty of Sciences, University of Porto (FCUP), 4169-007 Porto, Portugal
| | - Primo Micarelli
- The Sharks Studies Centre—Scientific Institute, 58024 Massa Marittima, Italy
| | | | - Giuseppe Rijllo
- Department of Biology, Ecology and Earth Sciences (DiBEST), University of Calabria, 87036 Rende, Italy
| | - Gianni Giglio
- Department of Biology, Ecology and Earth Sciences (DiBEST), University of Calabria, 87036 Rende, Italy
| | - Emilio Sperone
- Department of Biology, Ecology and Earth Sciences (DiBEST), University of Calabria, 87036 Rende, Italy
- Correspondence: (O.M.A.); (E.S.)
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Reinero FR, Sperone E, Giglio G, Pacifico A, Mahrer M, Micarelli P. Influence of Environmental Factors on Prey Discrimination of Bait-Attracted White Sharks from Gansbaai, South Africa. Animals (Basel) 2022; 12:ani12233276. [PMID: 36496796 PMCID: PMC9741310 DOI: 10.3390/ani12233276] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2022] [Revised: 11/19/2022] [Accepted: 11/22/2022] [Indexed: 11/27/2022] Open
Abstract
The influence of environmental factors on prey discrimination of bait-attracted white sharks was studied over a six-year period (2008-2013) at Dyer Island Nature Reserve (Gansbaai, South Africa). Across 240 bait-attracted feeding events observed in this period, both immature and mature white sharks were attracted by the seal-shaped decoy rather than the tuna bait, except for the years 2008 and 2011. Tide ranges, underwater visibility, water temperature, and sea conditions were, in decreasing order, the factors which drove white sharks to select the seal-shaped decoy. High tide lowered the minimum depth from which sharks could approach seals close to the shore, while extended visibility helped the sharks in making predatory choices towards the more energy-rich prey source, the odorless seal-shaped decoy. On the contrary, warmer water is associated with an increase in phytoplankton that reduces underwater visibility and increases the diversity of teleosts including tuna-a known prey of white sharks-driving the sharks to favor the tuna bait. Overall, sea conditions were almost always slightly rough, ensuring a good average underwater visibility. Recommendations for future research work at this site are presented.
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Affiliation(s)
- Francesca Romana Reinero
- Sharks Studies Center-Scientific Institute, 58024 Massa Marittima, Italy
- Correspondence: ; Tel.: +39-32-9685-2552
| | - Emilio Sperone
- Department of Biology, Ecology and Earth Sciences, University of Calabria, 87036 Rende, Italy
| | - Gianni Giglio
- Department of Biology, Ecology and Earth Sciences, University of Calabria, 87036 Rende, Italy
| | - Antonio Pacifico
- Sharks Studies Center-Scientific Institute, 58024 Massa Marittima, Italy
- Department of Political Science and CEFOP-LUISS, LUISS Guido Carli University, 00197 Rome, Italy
| | - Makenna Mahrer
- W. M. Keck Science Department, Claremont McKenna College, Claremont, CA 91711, USA
| | - Primo Micarelli
- Sharks Studies Center-Scientific Institute, 58024 Massa Marittima, Italy
- Department of Physical Sciences, Earth and Environment, University of Siena, 53100 Siena, Italy
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Papastamatiou YP, Mourier J, TinHan T, Luongo S, Hosoki S, Santana-Morales O, Hoyos-Padilla M. Social dynamics and individual hunting tactics of white sharks revealed by biologging. Biol Lett 2022; 18:20210599. [PMID: 35317626 PMCID: PMC8941395 DOI: 10.1098/rsbl.2021.0599] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Social foraging, where animals forage in groups, takes many forms but is less studied in marine predators as measuring social associations in the wild is challenging. We used biologging (activity, cameras and telemetry receivers) sensors to measure social associations and simultaneous behaviour, in white sharks (Carcharodon carcharias) off Guadalupe Island, Mexico. Animal-borne telemetry receivers revealed that sharks varied in the number of associations they formed and occurred most often when sharks were swimming in straight paths or when they were turning frequently. While many associations were likely random, there was evidence of some stronger associations. Sharks varied in the depths they used and their activity, with some individuals more active in shallow water while others were more active 200-300 m deep. We propose that white sharks associate with other individuals so they can inadvertently share information on the location or remains of large prey. However, there may be a wide range of individual variability in both behaviour and sociality. Biologging now enables social associations of animals to be measured, concurrent with measures of their behaviour, so that social foraging of large marine predators can be quantified in the wild.
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Affiliation(s)
- Yannis P. Papastamatiou
- Institute of Environment, Department of Biological Sciences, Florida International University, North Miami, FL, USA
| | - Johann Mourier
- UMS 3514 Plateforme Marine Stella Mare, Université de Corse Pasquale Paoli, 20620 Biguglia, France
| | - Thomas TinHan
- Institute of Environment, Department of Biological Sciences, Florida International University, North Miami, FL, USA
- Cooperative Institute for Marine and Atmospheric Research, University of Hawaii, Honolulu, HI, USA
| | - Sarah Luongo
- Institute of Environment, Department of Biological Sciences, Florida International University, North Miami, FL, USA
| | - Seiko Hosoki
- Institute of Environment, Department of Biological Sciences, Florida International University, North Miami, FL, USA
| | | | - Mauricio Hoyos-Padilla
- Pelagios Kakunjá A.C., La Paz, Mexico
- Fins Attached Marine Research and Conservation, Colorado Springs, CO, USA
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Ryan LA, Slip DJ, Chapuis L, Collin SP, Gennari E, Hemmi JM, How MJ, Huveneers C, Peddemors VM, Tosetto L, Hart NS. A shark's eye view: testing the 'mistaken identity theory' behind shark bites on humans. J R Soc Interface 2021; 18:20210533. [PMID: 34699727 PMCID: PMC8548079 DOI: 10.1098/rsif.2021.0533] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
Abstract
Shark bites on humans are rare but are sufficiently frequent to generate substantial public concern, which typically leads to measures to reduce their frequency. Unfortunately, we understand little about why sharks bite humans. One theory for bites occurring at the surface, e.g. on surfers, is that of mistaken identity, whereby sharks mistake humans for their typical prey (pinnipeds in the case of white sharks). This study tests the mistaken identity theory by comparing video footage of pinnipeds, humans swimming and humans paddling surfboards, from the perspective of a white shark viewing these objects from below. Videos were processed to reflect how a shark's retina would detect the visual motion and shape cues. Motion cues of humans swimming, humans paddling surfboards and pinnipeds swimming did not differ significantly. The shape of paddled surfboards and human swimmers was also similar to that of pinnipeds with their flippers abducted. The difference in shape between pinnipeds with abducted versus adducted flippers was bigger than between pinnipeds with flippers abducted and surfboards or human swimmers. From the perspective of a white shark, therefore, neither visual motion nor shape cues allow an unequivocal visual distinction between pinnipeds and humans, supporting the mistaken identity theory behind some bites.
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Affiliation(s)
- Laura A Ryan
- Department of Biological Sciences, Macquarie University, North Ryde, New South Wales 2109, Australia
| | - David J Slip
- Taronga Conservation Society Australia, Bradley's Head Road, Mosman, New South Wales 2088, Australia
| | - Lucille Chapuis
- Biosciences, College of Life and Environmental Sciences, University of Exeter, Exeter EX4 4QD, UK
| | - Shaun P Collin
- School of Life Sciences, La Trobe University, Bundoora, Victoria 3086, Australia
| | - Enrico Gennari
- Oceans Research Institute, Mossel Bay 6500, South Africa.,South African Institute for Aquatic Biodiversity, Private Bag 1015, Grahamstown 6140, South Africa.,Department of Ichthyology and Fisheries Science, Rhodes University, Grahamstown 6140, South Africa
| | - Jan M Hemmi
- School of Biological Sciences and The UWA Oceans Institute, M092, University of Western Australia, Perth, Western Australia 6009, Australia
| | - Martin J How
- School of Biological Sciences, University of Bristol, Bristol BS8 1TQ, UK
| | - Charlie Huveneers
- College of Science and Engineering, Flinders University, Bedford Park, South Australia 5042, Australia
| | - Victor M Peddemors
- New South Wales Department of Primary Industries, Sydney Institute of Marine Science, Mosman, New South Wales 2088, Australia
| | - Louise Tosetto
- Department of Biological Sciences, Macquarie University, North Ryde, New South Wales 2109, Australia
| | - Nathan S Hart
- Department of Biological Sciences, Macquarie University, North Ryde, New South Wales 2109, Australia
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Brown HKM, Rubega M, Dierssen HM. The light's in my eyes: optical modeling demonstrates wind is more important than sea surface-reflected sunlight for foraging herons. PeerJ 2021; 9:e12006. [PMID: 34692240 PMCID: PMC8485832 DOI: 10.7717/peerj.12006] [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: 08/24/2018] [Accepted: 07/27/2021] [Indexed: 11/20/2022] Open
Abstract
Multiple lineages of birds have independently evolved foraging strategies that involve catching aquatic prey by striking at them through the water’s surface. Diurnal, visual predators that hunt across the air-water interface encounter several visual challenges, including sun glint, or reflection of sunlight by the water surface. Intense sun glint is common at the air-water interface, and it obscures visual cues from submerged prey. Visually-hunting, cross-media predators must therefore solve the problem of glint to hunt effectively. One obvious solution is to turn away from the sun, which would result in reduction of glint effects. However, turning too far will cast shadows over prey, causing them to flee. Therefore, we hypothesized that foraging herons would orient away from, but not directly opposite to the sun. Our ability to understand how predators achieve a solution to glint is limited by our ability to quantify the amount of glint that free-living predators are actually exposed to under different light conditions. Herons (Ardea spp.) are a good model system for answering questions about cross-media hunting because they are conspicuous, widely distributed, and forage throughout a variety of aquatic habitats, on a variety of submerged prey. To test our hypothesis, we employed radiative transfer modeling of water surface reflectance, drawn from optical oceanography, in a novel context to estimate the visual exposure to glint of free-living, actively foraging herons. We found evidence that Ardea spp. do not use body orientation to compensate for sun glint while foraging and therefore they must have some other, not yet understood, means of compensation, either anatomical or behavioral. Instead of facing away from the sun, herons tended to adjust their position to face into the wind at higher wind speeds. We suggest that radiative transfer modeling is a promising tool for elucidating the ecology and evolution of air-to-water foraging systems.
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Affiliation(s)
- Holly K M Brown
- Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, CT, United States of America
| | - Margaret Rubega
- Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, CT, United States of America
| | - Heidi M Dierssen
- Department of Marine Sciences, University of Connecticut at Avery Point, Groton, CT, United States of America
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Bradshaw CJA, Meagher P, Thiele MJ, Harcourt RG, Huveneers C. Predicting potential future reduction in shark bites on people. ROYAL SOCIETY OPEN SCIENCE 2021; 8:201197. [PMID: 34035935 PMCID: PMC8101541 DOI: 10.1098/rsos.201197] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Accepted: 01/26/2021] [Indexed: 06/12/2023]
Abstract
Despite the low chance of a person being bitten by a shark, there are serious associated costs. Electronic deterrents are currently the only types of personal deterrent with empirical evidence of a substantial reduction in the probability of being bitten by a shark. We aimed to predict the number of people who could potentially avoid being bitten by sharks in Australia if they wear personal electronic deterrents. We used the Australian Shark Attack File from 1900 to 2020 to develop sinusoidal time-series models of per capita incidents, and then stochastically projected these to 2066. We predicted that up to 1063 people (range: 185-2118) could potentially avoid being bitten across Australia by 2066 if all people used the devices. Avoiding death and injury of people over the next half-century is of course highly desirable, especially when considering the additional costs associated with the loss of recreational, commercial and tourism revenue potentially in the tens to hundreds of millions of dollars following clusters of shark-bite events.
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Affiliation(s)
- Corey J. A. Bradshaw
- Global Ecology, College of Science and Engineering, Flinders University, GPO Box 2100, Adelaide, South Australia 5001, Australia
| | - Phoebe Meagher
- Taronga Conservation Society Australia, Taronga Zoo, Sydney, New South Wales, Australia
| | - Madeline J. Thiele
- Global Ecology, College of Science and Engineering, Flinders University, GPO Box 2100, Adelaide, South Australia 5001, Australia
- Southern Shark Ecology Group, College of Science and Engineering, Flinders University, GPO Box 2100, Adelaide, South Australia 5001, Australia
| | - Robert G. Harcourt
- Department of Biological Sciences, Macquarie University, Sydney, New South Wales 2109, Australia
| | - Charlie Huveneers
- Southern Shark Ecology Group, College of Science and Engineering, Flinders University, GPO Box 2100, Adelaide, South Australia 5001, Australia
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Brewster LR, Cahill BV, Burton MN, Dougan C, Herr JS, Norton LI, McGuire SA, Pico M, Urban-Gedamke E, Bassos-Hull K, Tyminski JP, Hueter RE, Wetherbee BM, Shivji M, Burnie N, Ajemian MJ. First insights into the vertical habitat use of the whitespotted eagle ray Aetobatus narinari revealed by pop-up satellite archival tags. JOURNAL OF FISH BIOLOGY 2021; 98:89-101. [PMID: 32985701 DOI: 10.1111/jfb.14560] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2020] [Revised: 09/21/2020] [Accepted: 09/24/2020] [Indexed: 06/11/2023]
Abstract
The whitespotted eagle ray Aetobatus narinari is a tropical to warm-temperate benthopelagic batoid that ranges widely throughout the western Atlantic Ocean. Despite conservation concerns for the species, its vertical habitat use and diving behaviour remain unknown. Patterns and drivers in the depth distribution of A. narinari were investigated at two separate locations, the western North Atlantic (Islands of Bermuda) and the eastern Gulf of Mexico (Sarasota, Florida, U.S.A.). Between 2010 and 2014, seven pop-up satellite archival tags were attached to A. narinari using three methods: a through-tail suture, an external tail-band and through-wing attachment. Retention time ranged from 0 to 180 days, with tags attached via the through-tail method retained longest. Tagged rays spent the majority of time (82.85 ± 12.17% S.D.) within the upper 10 m of the water column and, with one exception, no rays travelled deeper than ~26 m. One Bermuda ray recorded a maximum depth of 50.5 m, suggesting that these animals make excursions off the fore-reef slope of the Bermuda Platform. Individuals occupied deeper depths (7.42 ± 3.99 m S.D.) during the day versus night (4.90 ± 2.89 m S.D.), which may be explained by foraging and/or predator avoidance. Each individual experienced a significant difference in depth and temperature distributions over the diel cycle. There was evidence that mean hourly depth was best described by location and individual variation using a generalized additive mixed model approach. This is the first study to compare depth distributions of A. narinari from different locations and describe the thermal habitat for this species. Our study highlights the importance of region in describing A. narinari depth use, which may be relevant when developing management plans, whilst demonstrating that diel patterns appear to hold across individuals.
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Affiliation(s)
- Lauran R Brewster
- Harbor Branch Oceanographic Institute, Florida Atlantic University, Fort Pierce, Florida, USA
| | - Brianna V Cahill
- Harbor Branch Oceanographic Institute, Florida Atlantic University, Fort Pierce, Florida, USA
| | - Miranda N Burton
- Harbor Branch Oceanographic Institute, Florida Atlantic University, Fort Pierce, Florida, USA
| | - Cassady Dougan
- Harbor Branch Oceanographic Institute, Florida Atlantic University, Fort Pierce, Florida, USA
| | - Jeffrey S Herr
- Harbor Branch Oceanographic Institute, Florida Atlantic University, Fort Pierce, Florida, USA
| | - Laura Issac Norton
- Harbor Branch Oceanographic Institute, Florida Atlantic University, Fort Pierce, Florida, USA
| | - Samantha A McGuire
- Harbor Branch Oceanographic Institute, Florida Atlantic University, Fort Pierce, Florida, USA
| | - Marisa Pico
- Harbor Branch Oceanographic Institute, Florida Atlantic University, Fort Pierce, Florida, USA
| | - Elizabeth Urban-Gedamke
- Harbor Branch Oceanographic Institute, Florida Atlantic University, Fort Pierce, Florida, USA
| | - Kim Bassos-Hull
- Sharks and Rays Conservation Research Program, Mote Marine Laboratory, Sarasota, Florida, USA
| | - John P Tyminski
- Sharks and Rays Conservation Research Program, Mote Marine Laboratory, Sarasota, Florida, USA
| | - Robert E Hueter
- Sharks and Rays Conservation Research Program, Mote Marine Laboratory, Sarasota, Florida, USA
| | - Bradley M Wetherbee
- Department of Biological Sciences, University of Rhode Island, Kingston, Rhode Island, USA
- The Guy Harvey Research Institute, Nova Southeastern University, Dania Beach, Florida, USA
| | - Mahmood Shivji
- The Guy Harvey Research Institute, Nova Southeastern University, Dania Beach, Florida, USA
| | | | - Matthew J Ajemian
- Harbor Branch Oceanographic Institute, Florida Atlantic University, Fort Pierce, Florida, USA
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Winton MV, Sulikowski J, Skomal GB. Fine-scale vertical habitat use of white sharks at an emerging aggregation site and implications for public safety. WILDLIFE RESEARCH 2021. [DOI: 10.1071/wr20029] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Abstract
ContextOver the past decade, the coastal waters off Cape Cod, Massachusetts, have emerged as the only known aggregation site for the white shark (Carcharodon carcharias) in the western North Atlantic. During periods of seasonal residency, white sharks patrol the shoreline in search of pinniped prey, bringing them in close proximity to popular beaches where people recreate.
AimTo examine whether white sharks off Cape Cod are more likely to occupy shallow depths (and consequently more likely to overlap with recreational water users) under certain conditions.
MethodsWe deployed short-term, pop-up satellite archival transmitting (PSAT) tags and acoustic transmitters on 14 subadult and adult white sharks off the coast of Cape Cod during the summer and fall of 2017. PSAT tags provided fine-scale depth and temperature data, which were combined with high-resolution location data obtained from an acoustic telemetry array, to identify the depth and temperature preferences of white sharks when resident in the area.
Key resultsSharks spent the majority (95%) of tracked time at depths of 0–31m and at temperatures from 8.9°C to 20.7°C. During resident periods along Cape Cod, individuals spent almost half (47%) of their time at depths of less than 4.5m, but made frequent excursions to mid-shelf depths, alternating between the surf zone and deeper offshore waters. Sharks were slightly more likely to occupy shallow depths at night during the new moon. The relationship between shark depth and lunar phase varied over the course of the day, suggesting the mechanism underlying lunar effects differs among diel periods.
ConclusionsAlthough the overall risk posed to humans by white sharks is low, there is a high potential for overlap between white sharks and recreational water users off Cape Cod. The risk of interaction may be slightly higher during periods when local environmental conditions favour the species’ predatory stealth by influencing prey behaviour or detectability.
ImplicationsThis study provides the first glimpse into the fine-scale vertical habitat use of white sharks off Cape Cod, which can be used to better understand the risk to recreational water users and to inform public safety practices.
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Pembury Smith MQR, Ruxton GD. Camouflage in predators. Biol Rev Camb Philos Soc 2020; 95:1325-1340. [DOI: 10.1111/brv.12612] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2020] [Revised: 04/24/2020] [Accepted: 04/28/2020] [Indexed: 12/29/2022]
Affiliation(s)
| | - Graeme D. Ruxton
- School of Biology University of St Andrews, Dyers Brae House, St Andrews Fife KY16 9TH U.K
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Nebel C, Sumasgutner P, Pajot A, Amar A. Response time of an avian prey to a simulated hawk attack is slower in darker conditions, but is independent of hawk colour morph. ROYAL SOCIETY OPEN SCIENCE 2019; 6:190677. [PMID: 31598248 PMCID: PMC6731706 DOI: 10.1098/rsos.190677] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/10/2019] [Accepted: 07/08/2019] [Indexed: 06/10/2023]
Abstract
To avoid predation, many species rely on vision to detect predators and initiate an escape response. The ability to detect predators may be lower in darker light conditions or with darker backgrounds. For birds, however, this has never been experimentally tested. We test the hypothesis that the response time of avian prey (feral pigeon Columbia livia f. domestica) to a simulated hawk attack (taxidermy mounted colour-polymorphic black sparrowhawk Accipiter melanoleucus) will differ depending on light levels or background colour. We predict that response will be slower under darker conditions, which would translate into higher predation risk. The speed of response of prey in relation to light level or background colour may also interact with the colour of the predator, and this idea underpins a key hypothesis proposed for the maintenance of different colour morphs in polymorphic raptors. We therefore test whether the speed of reaction is influenced by the morph of the hawk (dark/light) in combination with light conditions (dull/bright), or background colours (black/white). We predict slowest responses to morphs under conditions that less contrast with the plumage of the hawk (e.g. light morph under bright light or white background). In support of our first hypothesis, pigeons reacted slower under duller light and with a black background. However, we found no support for the second hypothesis, with response times observed between the hawk-morphs being irrespective of light levels or background colour. Our findings experimentally confirm that birds detect avian predators less efficiently under darker conditions. These conditions, for example, might occur during early mornings or in dense forests, which could lead to changes in anti-predator behaviours. However, our results provide no support that different morphs may be maintained in a population due to differential selective advantages linked to improved hunting efficiencies in different conditions due to crypsis.
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Affiliation(s)
- Carina Nebel
- FitzPatrick Institute of African Ornithology, DST-NRF Centre of Excellence, University of Cape Town, Private Bag X3, Rondebosch, 7701 Cape Town, South Africa
| | - Petra Sumasgutner
- FitzPatrick Institute of African Ornithology, DST-NRF Centre of Excellence, University of Cape Town, Private Bag X3, Rondebosch, 7701 Cape Town, South Africa
| | - Adrien Pajot
- FitzPatrick Institute of African Ornithology, DST-NRF Centre of Excellence, University of Cape Town, Private Bag X3, Rondebosch, 7701 Cape Town, South Africa
- Bordeaux Sciences Agro, 1 Cours du Général de Gaulle, 33170 Gradignan, France
| | - Arjun Amar
- FitzPatrick Institute of African Ornithology, DST-NRF Centre of Excellence, University of Cape Town, Private Bag X3, Rondebosch, 7701 Cape Town, South Africa
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12
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Stevens M, Ruxton GD. The key role of behaviour in animal camouflage. Biol Rev Camb Philos Soc 2019; 94:116-134. [PMID: 29927061 PMCID: PMC6378595 DOI: 10.1111/brv.12438] [Citation(s) in RCA: 73] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2018] [Revised: 05/25/2018] [Accepted: 05/31/2018] [Indexed: 01/24/2023]
Abstract
Animal camouflage represents one of the most important ways of preventing (or facilitating) predation. It attracted the attention of the earliest evolutionary biologists, and today remains a focus of investigation in areas ranging from evolutionary ecology, animal decision-making, optimal strategies, visual psychology, computer science, to materials science. Most work focuses on the role of animal morphology per se, and its interactions with the background in affecting detection and recognition. However, the behaviour of organisms is likely to be crucial in affecting camouflage too, through background choice, body orientation and positioning; and strategies of camouflage that require movement. A wealth of potential mechanisms may affect such behaviours, from imprinting and self-assessment to genetics, and operate at several levels (species, morph, and individual). Over many years there have been numerous studies investigating the role of behaviour in camouflage, but to date, no effort to synthesise these studies and ideas into a coherent framework. Here, we review key work on behaviour and camouflage, highlight the mechanisms involved and implications of behaviour, discuss the importance of this in a changing world, and offer suggestions for addressing the many important gaps in our understanding of this subject.
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Affiliation(s)
- Martin Stevens
- Centre for Ecology and Conservation, College of Life and Environmental SciencesUniversity of Exeter, Penryn CampusPenryn, TR10 9FEU.K.
| | - Graeme D. Ruxton
- School of BiologyUniversity of St AndrewsSt Andrews, KY16 9THU.K.
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13
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Collin SP. Scene through the eyes of an apex predator: a comparative analysis of the shark visual system. Clin Exp Optom 2018; 101:624-640. [PMID: 30066959 DOI: 10.1111/cxo.12823] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2018] [Revised: 07/09/2018] [Accepted: 07/09/2018] [Indexed: 12/15/2022] Open
Abstract
The eyes of apex predators, such as the shark, have fascinated comparative visual neuroscientists for hundreds of years with respect to how they perceive the dark depths of their ocean realm or the visual scene in search of prey. As the earliest representatives of the first stage in the evolution of jawed vertebrates, sharks have an important role to play in our understanding of the evolution of the vertebrate eye, including that of humans. This comprehensive review covers the structure and function of all the major ocular components in sharks and how they are adapted to a range of underwater light environments. A comparative approach is used to identify: species-specific diversity in the perception of clear optical images; photoreception for various visual behaviours; the trade-off between image resolution and sensitivity; and visual processing under a range of levels of illumination. The application of this knowledge is also discussed with respect to the conservation of this important group of cartilaginous fishes.
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Affiliation(s)
- Shaun P Collin
- The Oceans Institute and the Oceans Graduate School, The University of Western Australia, Perth, Western Australia, Australia
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Goldbogen JA, Madsen PT. The evolution of foraging capacity and gigantism in cetaceans. ACTA ACUST UNITED AC 2018; 221:221/11/jeb166033. [PMID: 29895582 DOI: 10.1242/jeb.166033] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The extant diversity and rich fossil record of cetaceans provides an extraordinary evolutionary context for investigating the relationship between form, function and ecology. The transition from terrestrial to marine ecosystems is associated with a complex suite of morphological and physiological adaptations that were required for a fully aquatic mammalian life history. Two specific functional innovations that characterize the two great clades of cetaceans, echolocation in toothed whales (Odontoceti) and filter feeding in baleen whales (Mysticeti), provide a powerful comparative framework for integrative studies. Both clades exhibit gigantism in multiple species, but we posit that large body size may have evolved for different reasons and in response to different ecosystem conditions. Although these foraging adaptations have been studied using a combination of experimental and tagging studies, the precise functional drivers and consequences of morphological change within and among these lineages remain less understood. Future studies that focus at the interface of physiology, ecology and paleontology will help elucidate how cetaceans became the largest predators in aquatic ecosystems worldwide.
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Affiliation(s)
- J A Goldbogen
- Department of Biology, Hopkins Marine Station, Stanford University, 120 Ocean View Boulevard, Pacific Grove, CA 93950, USA
| | - P T Madsen
- Zoophysiology, Department of Bioscience, Aarhus University, C.F. Møllers Allé 3, 8000 Aarhus C, Denmark.,Aarhus Institute of Advanced Studies, Høegh-Guldbergs Gade 6B, DK-8000 Aarhus C, Denmark
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15
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Huveneers C, Watanabe YY, Payne NL, Semmens JM. Interacting with wildlife tourism increases activity of white sharks. CONSERVATION PHYSIOLOGY 2018; 6:coy019. [PMID: 29780593 PMCID: PMC5912080 DOI: 10.1093/conphys/coy019] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Revised: 03/22/2018] [Accepted: 04/04/2018] [Indexed: 05/30/2023]
Abstract
Anthropogenic activities are dramatically changing marine ecosystems. Wildlife tourism is one of the fastest growing sectors of the tourism industry and has the potential to modify the natural environment and behaviour of the species it targets. Here, we used a novel method to assess the effects of wildlife tourism on the activity of white sharks (Carcharodon carcharias). High frequency three-axis acceleration loggers were deployed on ten white sharks for a total of ~9 days. A combination of multivariate and univariate analysis revealed that the increased number of strong accelerations and vertical movements when sharks are interacting with cage-diving operators result in an overall dynamic body acceleration (ODBA) ~61% higher compared with other times when sharks are present in the area where cage-diving occurs. Since ODBA is considered a proxy of metabolic rate, interacting with cage-divers is probably more costly than are normal behaviours of white sharks at the Neptune Islands. However, the overall impact of cage-diving might be small if interactions with individual sharks are infrequent. This study suggests wildlife tourism changes the instantaneous activity levels of white sharks, and calls for an understanding of the frequency of shark-tourism interactions to appreciate the net impact of ecotourism on this species' fitness.
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Affiliation(s)
- Charlie Huveneers
- College of Science and Engineering, Flinders University, Bedford Park, Adelaide, South Australia 5165, Australia
| | - Yuuki Y Watanabe
- National Institute of Polar Research, Tachikawa, Tokyo 190-8518, Japan
- SOKENDAI (The Graduate University for Advanced Studies), Tachikawa, Tokyo 190-8518, Japan
| | - Nicholas L Payne
- National Institute of Polar Research, Tachikawa, Tokyo 190-8518, Japan
- University of Roehampton, London SW154JD, UK
| | - Jayson M Semmens
- Fisheries and Aquaculture Centre, Institute for Marine and Antarctic Studies, University of Tasmania, Taroona, Tasmania 7053, Australia
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16
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French GCA, Rizzuto S, Stürup M, Inger R, Barker S, van Wyk JH, Towner AV, Hughes WOH. Sex, size and isotopes: cryptic trophic ecology of an apex predator, the white shark Carcharodon carcharias. MARINE BIOLOGY 2018; 165:102. [PMID: 29780176 PMCID: PMC5958155 DOI: 10.1007/s00227-018-3343-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/08/2017] [Accepted: 04/03/2018] [Indexed: 06/08/2023]
Abstract
Demographic differences in resource use are key components of population and species ecology across the animal kingdom. White sharks (Carcharodon carcharias) are migratory, apex predators, which have undergone significant population declines across their range. Understanding their ecology is key to ensuring that management strategies are effective. Here, we carry out the first stable isotope analyses of free-swimming white sharks in South Africa. Biopsies were collected in Gansbaai (34.5805°S, 19.3518°E) between February and July 2015. We used Stable Isotope Bayesian Ellipsis in R and traditional statistical analyses to quantify and compare isotopic niches of male and female sharks of two size classes, and analyse relationships between isotopic values and shark length. Our results reveal cryptic trophic differences between the sexes and life stages. Males, but not females, were inferred to feed in more offshore or westerly habitats as they grow larger, and only males exhibited evidence of an ontogenetic niche shift. Lack of relationship between δ13C, δ15N and female shark length may be caused by females exhibiting multiple migration and foraging strategies, and a greater propensity to travel further north. Sharks < 3 m had much wider, and more diverse niches than sharks > 3 m, drivers of which may include individual dietary specialisation and temporal factors. The differences in migratory and foraging behaviour between sexes, life stages, and individuals will affect their exposure to anthropogenic threats, and should be considered in management strategies.
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Affiliation(s)
- G. C. A. French
- School of Life Sciences, University of Sussex, Brighton, BN1 9QG UK
| | - S. Rizzuto
- Department of Botany and Zoology, Stellenbosch University, Merriam Avenue, Stellenbosch, 7600 South Africa
| | - M. Stürup
- School of Life Sciences, University of Sussex, Brighton, BN1 9QG UK
| | - R. Inger
- Environment and Sustainability Unit, University of Exeter, Penryn Campus, Penryn, Cornwall TR10 9FE UK
| | - S. Barker
- Environment and Sustainability Unit, University of Exeter, Penryn Campus, Penryn, Cornwall TR10 9FE UK
| | - J. H. van Wyk
- Department of Botany and Zoology, Stellenbosch University, Merriam Avenue, Stellenbosch, 7600 South Africa
| | - A. V. Towner
- Dyer Island Conservation Trust, Kleinbaai, South Africa
| | - W. O. H. Hughes
- School of Life Sciences, University of Sussex, Brighton, BN1 9QG UK
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17
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French GCA, Stürup M, Rizzuto S, van Wyk JH, Edwards D, Dolan RW, Wintner SP, Towner AV, Hughes WOH. The tooth, the whole tooth and nothing but the tooth: tooth shape and ontogenetic shift dynamics in the white shark Carcharodon carcharias. JOURNAL OF FISH BIOLOGY 2017; 91:1032-1047. [PMID: 28815588 DOI: 10.1111/jfb.13396] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2017] [Accepted: 07/18/2017] [Indexed: 06/07/2023]
Abstract
Results from this study of the white shark Carcharodon carcharias include measurements obtained using a novel photographic method that reveal significant differences between the sexes in the relationship between tooth cuspidity and shark total length, and a novel ontogenetic change in male tooth shape. Males exhibit broader upper first teeth and increased distal inclination of upper third teeth with increasing length, while females do not present a consistent morphological change. Substantial individual variation, with implications for pace of life syndrome, was present in males and tooth polymorphism was suggested in females. Sexual differences and individual variation may play major roles in ontogenetic changes in tooth morphology in C. carcharias, with potential implications for their foraging biology. Such individual and sexual differences should be included in studies of ontogenetic shift dynamics in other species and systems.
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Affiliation(s)
- G C A French
- School of Life Sciences, University of Sussex, Brighton, BN1 9QG, U.K
| | - M Stürup
- School of Life Sciences, University of Sussex, Brighton, BN1 9QG, U.K
| | - S Rizzuto
- Department of Botany and Zoology, Stellenbosch University, Stellenbosch, 7600, South Africa
| | - J H van Wyk
- Department of Botany and Zoology, Stellenbosch University, Stellenbosch, 7600, South Africa
| | - D Edwards
- Dyer Island Conservation Trust, Kleinbaai, South Africa
| | - R W Dolan
- Dyer Island Conservation Trust, Kleinbaai, South Africa
| | - S P Wintner
- KwaZulu-Natal Sharks Board and Biomedical Resource Unit, University of KwaZulu-Natal, Durban, 4000, South Africa
| | - A V Towner
- Dyer Island Conservation Trust, Kleinbaai, South Africa
| | - W O H Hughes
- School of Life Sciences, University of Sussex, Brighton, BN1 9QG, U.K
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18
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Goldbogen JA, Cade DE, Calambokidis J, Friedlaender AS, Potvin J, Segre PS, Werth AJ. How Baleen Whales Feed: The Biomechanics of Engulfment and Filtration. ANNUAL REVIEW OF MARINE SCIENCE 2017; 9:367-386. [PMID: 27620830 DOI: 10.1146/annurev-marine-122414-033905] [Citation(s) in RCA: 88] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Baleen whales are gigantic obligate filter feeders that exploit aggregations of small-bodied prey in littoral, epipelagic, and mesopelagic ecosystems. At the extreme of maximum body size observed among mammals, baleen whales exhibit a unique combination of high overall energetic demands and low mass-specific metabolic rates. As a result, most baleen whale species have evolved filter-feeding mechanisms and foraging strategies that take advantage of seasonally abundant yet patchily and ephemerally distributed prey resources. New methodologies consisting of multi-sensor tags, active acoustic prey mapping, and hydrodynamic modeling have revolutionized our ability to study the physiology and ecology of baleen whale feeding mechanisms. Here, we review the current state of the field by exploring several hypotheses that aim to explain how baleen whales feed. Despite significant advances, major questions remain about the processes that underlie these extreme feeding mechanisms, which enabled the evolution of the largest animals of all time.
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Affiliation(s)
- J A Goldbogen
- Department of Biology, Hopkins Marine Station, Stanford University, Pacific Grove, California 93950; , ,
| | - D E Cade
- Department of Biology, Hopkins Marine Station, Stanford University, Pacific Grove, California 93950; , ,
| | - J Calambokidis
- Cascadia Research Collective, Olympia, Washington 98501;
| | - A S Friedlaender
- Department of Fisheries and Wildlife, Marine Mammal Institute, Hatfield Marine Science Center, Oregon State University, Newport, Oregon 97365;
| | - J Potvin
- Department of Physics, Saint Louis University, St. Louis, Missouri 63103;
| | - P S Segre
- Department of Biology, Hopkins Marine Station, Stanford University, Pacific Grove, California 93950; , ,
| | - A J Werth
- Department of Biology, Hampden-Sydney College, Hampden-Sydney, Virginia 23943;
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19
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Skomal GB, Hoyos-Padilla EM, Kukulya A, Stokey R. Subsurface observations of white shark Carcharodon carcharias predatory behaviour using an autonomous underwater vehicle. JOURNAL OF FISH BIOLOGY 2015; 87:1293-1312. [PMID: 26709209 DOI: 10.1111/jfb.12828] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2015] [Accepted: 09/30/2015] [Indexed: 06/05/2023]
Abstract
In this study, an autonomous underwater vehicle (AUV) was used to test this technology as a viable tool for directly observing the behaviour of marine animals and to investigate the behaviour, habitat use and feeding ecology of white sharks Carcharodon carcharias near Guadalupe Island off the coast of Mexico. During the period 31 October to 7 November 2013, six AUV missions were conducted to track one male and three female C. carcharias, ranging in estimated total length (LT ) from 3·9 to 5·7 m, off the north-east coast of Guadalupe Island. In doing so, the AUV generated over 13 h of behavioural data for C. carcharias at depths down to 90 m. The sharks remained in the area for the duration of each mission and moved through broad depth and temperature ranges from the surface to 163·8 m depth (mean ± S.D. = 112·5 ± 40·3 m) and 7·9-27·1° C (mean ± S.D. = 12·7 ± 2·9° C), respectively. Video footage and AUV sensor data revealed that two of the C. carcharias being tracked and eight other C. carcharias in the area approached (n = 17), bumped (n = 4) and bit (n = 9) the AUV during these tracks. This study demonstrated that an AUV can be used to effectively track and observe the behaviour of a large pelagic animal, C. carcharias. In doing so, the first observations of subsurface predatory behaviour were generated for this species. At its current state of development, this technology clearly offers a new and innovative tool for tracking the fine-scale behaviour of marine animals.
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Affiliation(s)
- G B Skomal
- Massachusetts Division of Marine Fisheries, 1213 Purchase St., New Bedford, MA 02740, U.S.A
| | - E M Hoyos-Padilla
- Pelagios-Kakunja A.C. Sinaloa 1540, Col. Las Garzas, C. P. 23070, La Paz, Baja California Sur, Mexico
| | - A Kukulya
- Oceanographic Systems Laboratory, Woods Hole Oceanographic Institution, 86 Water St., Woods Hole, MA 02543, U.S.A
| | - R Stokey
- Oceanographic Systems Laboratory, Woods Hole Oceanographic Institution, 86 Water St., Woods Hole, MA 02543, U.S.A
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