Article

Behavioural patterns of a Tiger Shark (Galeocerdo cuvier) feeding aggregation at a blue whale carcass in Prony Bay, New Caledonia

Authors:
  • Province Sud
To read the full-text of this research, you can request a copy directly from the authors.

Abstract

Tiger Sharks, Galeocerdo cuvier, are large top-level predators usually solitary as adults. Observation of their scavenging activity on the carcass of a dead whale offered a rare opportunity for better understanding the pattern of intra-specific behaviour within the aggregations of these large predators. In January 2002, the stranding, subsequent death and consumption of a 17.4m total length (TL) blue whale, Balaenoptera musculus, was observed and filmed in Prony Bay, southern New Caledonia. After three weeks of confinement in the bay, the cetacean was killed by adult bullsharks Carcharhinus leucas. The first adult Tiger Shark was subsequently observed around the carcass after 36h. The fat slicks from the carcass attracted further Tiger Sharks which arrived after an additional 24h. The use of photo-identification on video footage collected during four observation sessions over an eight-day period identified 46 individual Tiger Sharks (primarily adult females between 3.3 and 4m TL) participating in the feeding aggregation. Only four animals were identified in two seperate observation sessions (over two consecutive days), suggesting a short-term residency pattern of several hours (<36h) around the carcass. As the arrival time of Tiger Sharks to the carcass differed, most arrivals of a new participant were followed by a frenzied period of intense intra-specific interaction. Different biting and agonistic behaviours were demonstrated by the Tiger Sharks on the carcass, including three new behaviours previously undescribed for this species. Size and level of aggressiveness appeared to be the determining factors of dominance amongst Tiger Sharks. These observations and analysis demonstrate that systematic study of feeding aggregations supported by photo-identification could contribute to knowledge of large shark ecology when coupled with capture-recapture, genetic fingerprinting and tagging techniques.

No full-text available

Request Full-text Paper PDF

To read the full-text of this research,
you can request a copy directly from the authors.

... Sharks remained docile in this position while morphometrics of total length (TL) (cm) and gender were recorded. Dorsal fins and distinguishing body features of all captured sharks and tiger sharks that broke away from baited lines before tagging were photographed as per Clua et al. [55]. The harness also enabled the opportunistic identification of stomach contents for sharks that regurgitated their contents after capture and restraint in the harness. ...
... Our study demonstrates extraordinary reef fidelity among tiger sharks in New Caledonia and the Chesterfield reefs. In New Caledonia, dorsal fin photo-ID of TS5 confirmed this shark was present in Prony Bay, New Caledonia, in 2002 on a whale carcass [55] and in 2008. As far as we are aware, this is the longest confirmed record of site-fidelity for a large tiger shark. ...
... Arrows highlight the distinguishing features of the individual sharks fin. Note A1 was identified by Clua et al. [55]. The photo taken in A3 is after a tissue sample was taken from the second notch in the shark's dorsal fin. ...
Article
Full-text available
Knowledge of the habitat use and migration patterns of large sharks is important for assessing the effectiveness of large predator Marine Protected Areas (MPAs), vulnerability to fisheries and environmental influences, and management of shark-human interactions. Here we compare movement, reef-fidelity, and ocean migration for tiger sharks, Galeocerdo cuvier, across the Coral Sea, with an emphasis on New Caledonia. Thirty-three tiger sharks (1.54 to 3.9 m total length) were tagged with passive acoustic transmitters and their localised movements monitored on receiver arrays in New Caledonia, the Chesterfield and Lord Howe Islands in the Coral Sea, and the east coast of Queensland, Australia. Satellite tags were also used to determine habitat use and movements among habitats across the Coral Sea. Sub-adults and one male adult tiger shark displayed year-round residency in the Chesterfields with two females tagged in the Chesterfields and detected on the Great Barrier Reef, Australia, after 591 and 842 days respectively. In coastal barrier reefs, tiger sharks were transient at acoustic arrays and each individual demonstrated a unique pattern of occurrence. From 2009 to 2013, fourteen sharks with satellite and acoustic tags undertook wide-ranging movements up to 1114 km across the Coral Sea with eight detected back on acoustic arrays up to 405 days after being tagged. Tiger sharks dove 1136 m and utilised three-dimensional activity spaces averaged at 2360 km(3). The Chesterfield Islands appear to be important habitat for sub-adults and adult male tiger sharks. Management strategies need to consider the wide-ranging movements of large (sub-adult and adult) male and female tiger sharks at the individual level, whereas fidelity to specific coastal reefs may be consistent across groups of individuals. Coastal barrier reef MPAs, however, only afford brief protection for large tiger sharks, therefore determining the importance of other oceanic Coral Sea reefs should be a priority for future research.
... Despite the numerous studies dealing with stomach contents of extant tiger sharks (e.g. Bass et al. 1975;Stevens and Mc Loughlin 1991;Randall 1992;Lowe et al. 1996;Simpfendorfer et al. 2001;Dicken et al. 2017) and their feeding behaviour (Clua et al. 2013;Gallagher et al. 2018;Lea et al. 2019), reports on the feeding habits of the extinct tiger sharks are scarce and limited to indirect evidence (Applegate 1965;Cicimurri and Knight 2009). In rare cases, however, fossil stomach contents of some other sharks (e.g. ...
... Although tiger sharks are known to be mainly solitary predators, they gather and tolerate each other when feeding (Compagno et al. 2005;Clua et al. 2013;Lea et al. 2019). A study focusing on the feeding behaviour of tiger sharks foraging upon a large whale carcass demonstrated the tolerance of conspecifics during feeding (Clua et al. 2013). ...
... Although tiger sharks are known to be mainly solitary predators, they gather and tolerate each other when feeding (Compagno et al. 2005;Clua et al. 2013;Lea et al. 2019). A study focusing on the feeding behaviour of tiger sharks foraging upon a large whale carcass demonstrated the tolerance of conspecifics during feeding (Clua et al. 2013). To tear flesh off the carcass, the sharks, mostly comprising larger-sized individuals (>3.5 m TL), used a saw-biting technique (Clua et al. 2013), which might also have caused the bite marks that are found on the sirenian ribs studied herein (Figure 2 (B-F)). ...
Article
Based on a shark-bitten partial skeleton of an immature sirenian (Metaxytherium cf. medium) from the middle Miocene of the Styrian Basin (Austria), we report on the oldest predator–prey interaction between tiger sharks and dugongs. The bite mark-bearing ribs and vertebrae are associated with seven teeth of Galeocerdo aduncus, which are otherwise rare in the fossil record of the Styrian Basin. The unique tooth morphology of the genus Galeocerdo is reflected by an unambiguous pattern of bite marks, which is repeatedly detected on one rib fragment. Similar bite marks were reproduced experimentally by using clay instead of bone. The obtained pattern is consistent with the observed bite marks on the sirenian rib fragment, which demonstrates that tiger sharks fed upon the Metaxytherium carcass. Furthermore, we also report on the first record of the angel shark Squatina sp. within the Styrian Basin.
... Although the lack of data does not allow to 1 Mono or multi-specific aggregations of aquatic predators, esp. sharks, which get excited by a feeding stimulus, leading to frenetic and agonistic behaviours to access the food, with a decreased level of vigilance, biting anything within biting range, including other animals or inert materials (Clua et al. 2013). ...
... As shark density increases around prey or food, competition also increases leading to more active swimming and increased aggressive behaviours (particularly from new arrivals) or reduced time to feeding via cyclical social reinforcement (Guttridge et al., 2013). However, this collective behaviour temporarily increases the aggressiveness of participants toward conspecifics, other animals (including humans) or even inert devices (such as divers' flippers, boat motors, paddles, etc.) that are close to the food source (Clua, Chauvet, Read, Werry, & Lee, 2013;Nelson & Johnson, 1980). Although it did not modify the lemon sharks behaviour, the repetitive triggering at the surface of feeding frenzies involving them, would definitely increase the bite risk for humans in close proximity. ...
... NB: As described in Clua et al. (2010) the mating period of a given shark species would globally increase the level of risk, whatever the other parameters of the assessment. In particular during the mating season which adds sexual competition to the access to food (see Clua et al. 2010 Clua et al. (2013). In addition to the number of animals, which plays a facilitating role, the quantity and size of the food offered would play a critical role. ...
... Tiger Sharks in this study were less standardised on approach suggesting that the shape and mechanics of the tiger shark head allowed it to feed differently than white sharks. Clua et al. (2013) reported tiger sharks having feeding preference to the throat, supporting the theory that they prefer different areas to white sharks. The 45 angle to surface feeding was the most common technique, however, they did not appear to be as dependant on this method as white sharks. ...
... This variation of head shaking seems to be specific to tiger sharks whose serrated teeth have evolved to saw through large food sources and is consistent with past observations (Frazzetta, 1988). Unlike white sharks, this sawing behaviour was also accompanied by body twisting, a behaviour seen in other studies (Clua et al., 2013;Dudley et al., 2000;Lea et al., 2018). Ocular rotation is used by sharks to protect their eyes while feeding. ...
... Although most previous observations show a feeding preference for blubber there are differences in preference to areas of a carcass. Clua et al. (2013) described feeding preference to the tail, caudal peduncle and throat of a blue whale carcass by tiger sharks. Observations by Curtis et al. (2006) differ, describing preference to the flukes, tail and mid-section of a humpback whale by white sharks. ...
Article
Full-text available
Sharks are well known to scavenge whale carcasses, but observations are rare. Here we (1) describe new observations of whale carcass scavenging behaviour by white (Carcharodon carcharias) and tiger (Galeocerdo cuvier) sharks, and (2) review the scientific and grey literature on the topic. Our new observations are from the east coast of New South Wales, Australia and include a sperm whale (Physeter microcephalus) carcass in 2015, a humpback whale (Megaptera novaeangliae) carcass and fin whale (Balaenoptera physalus) carcass in 2018. Analysis of these observations revealed that feeding preferences differed among whale species for each species of shark. Feeding behaviour (including test biting, head shaking, palatoquadrate protrusion, ocular rotation and nictitating membrane use) were employed by both tiger and white sharks, with little inter or intraspecific aggression. Behaviour of sharks scavenging whale carcasses differs in the primary literature depending on whale carcass and species of shark present. Most of our results support past observations regarding feeding behaviours and little inter or intraspecific aggression. However, our results differed from past events. We observed increased palatoquadrate protrusion by white sharks and avoidance of flukes or pectoral fins feeding by tiger and white sharks. Review of the literature demonstrates that scavenging events are more commonly reported in grey literature than in scientific documents. Keywords: White shark, Carcharodon carcharias, Tiger shark, Galeocerdo cuvier, Whale, Scavenge
... Multiple tiger sharks have been documented cooperatively feeding alongside a saltwater crocodile on a humpback whale carcass (Gallagher et al. 2018). In another event, a blue whale (Balaenoptera musculus) carcass attracted 46 individual tiger sharks, feeding over 8 days (Clua et al. 2013;Gallagher et al. 2018). In events with inter-and intraspecies competition, cannibalism is a concern, and so size-based dominance hierarchies are often present with an increased tolerance towards smaller sharks over time (Clua et al. 2013). ...
... In another event, a blue whale (Balaenoptera musculus) carcass attracted 46 individual tiger sharks, feeding over 8 days (Clua et al. 2013;Gallagher et al. 2018). In events with inter-and intraspecies competition, cannibalism is a concern, and so size-based dominance hierarchies are often present with an increased tolerance towards smaller sharks over time (Clua et al. 2013). There were no concurrent behaviours observed between the two white sharks during this event. ...
... In January 2002, bull sharks (Carcharhinus leucas) attacked the tail and throat of a live blue whale (B. musculus), which caused intense bleeding and eventually death (Clua et al. 2013). Shark bites and scars on small odontocetes also follow this pattern, focusing around the posterior of the animal (Cockcroft et al. 1989). ...
Article
Full-text available
To date, white shark (Carcharodon carcharias) feeding events involving large whales have largely been described only in terms of observed scavenging events. Scavenging occurs in all ecosystems and is usually associated with stochastic feeding events. In marine ecosystems, whale carcasses commonly provide these community-wide food web events. Whale carcasses are the single largest source of carrion in marine ecosystems, to the extent that they are thought to constitute an important part of large white shark foraging ecology, shaping many aspects of the life history of the sharks, including adult migrations. However, to date, no part of this white shark feeding event has been described involving a live whale. To the best of our knowledge, here we provide the first published description of white sharks attacking and killing a live humpback whale (Megaptera novaeangliae). The attack displayed novel behaviours, including evidence of the ‘bite and spit’ tactic, rarely described in non-pinniped-related white shark feeding events before and all part of a tactical timeline of an attack that is precise, deliberate and effective.
... Cetacean carcasses perhaps represent the most significant form of energy windfall to scavengers, with some deep-sea communities seemingly surviving exclusively from whale falls (Smith and Baco 2003). Large whale carcasses can aggregate significant numbers of highly mobile, and usually solitary, predators that may normally be sparsely distributed, providing a rare opportunity to study their community structure and scavenging behaviours, including social interactions (Dudley et al. 2000;Clua et al. 2013). The available literature suggests that scavenging of cetacean carcasses at the surface is typically dominated by large lamnids and carcharhinids, with contrasting reports as to the degree of agonistic and competitive behaviours exhibited by scavengers (Long and Jones 1996;Dudley et al. 2000;Curtis et al. 2006;Bornatowski et al. 2012;Clua et al. 2013;Fallows et al. 2013;Hammerschlag et al. 2016;Gallagher et al. 2018). ...
... Large whale carcasses can aggregate significant numbers of highly mobile, and usually solitary, predators that may normally be sparsely distributed, providing a rare opportunity to study their community structure and scavenging behaviours, including social interactions (Dudley et al. 2000;Clua et al. 2013). The available literature suggests that scavenging of cetacean carcasses at the surface is typically dominated by large lamnids and carcharhinids, with contrasting reports as to the degree of agonistic and competitive behaviours exhibited by scavengers (Long and Jones 1996;Dudley et al. 2000;Curtis et al. 2006;Bornatowski et al. 2012;Clua et al. 2013;Fallows et al. 2013;Hammerschlag et al. 2016;Gallagher et al. 2018). ...
... The number of individuals recorded is likely to be conservative because of limited recording time and difficulty identifying sharks without discernible markings. Given that individual shark residence around other whale carcasses has been brief (,36 h; Clua et al. 2013), the actual number of individuals this carcass supported could have been substantially higher than the 31 identified. The abundance of tiger sharks is notable because, in over 5 years of extensive shark tracking and survey work in the Amirantes Islands, the authors had not previously encountered a single tiger shark. ...
Article
A drone was used to study the richness and behaviour of scavengers attracted to the carcass of a sperm whale (Physeter microcephalus) in Seychelles, Western Indian Ocean. Over 30 sharks of 3 species (tiger shark Galeocerdo cuvier, bull shark Carcharhinus leucas and tawny nurse shark Nebrius ferrugineus) were recorded scavenging on the carcass. Tiger sharks dominated the scavenging, but with no evidence of agonistic behaviours or hierarchy, and may have facilitated scavenging by other species. Drone use allowed the analysis of such behaviours without observer influence, providing new insights into communal scavenging events.
... It is becoming evident, however, that grouping in many species of elasmobranchs is common (e.g., Bass et al., 2016), as are complex social behaviors (e.g., Sims et al., 2000;Furst, 2011;Mourier et al., 2017a;Papastamatiou et al., 2020). Elasmobranch species that group often exhibit both social congregation (i.e., for reproduction, e.g., Port Jackson sharks (Heterondontus portusjacksonii), Bass et al., 2016) and non-social aggregation (i.e., attraction to limited resources; e.g., white (Carcharodon carcharias) and tiger sharks (Galeocardo cuvier), Clua et al., 2013). In some cases, non-social grouping may also be a condition under which social grouping later develops [e.g., basking sharks (Cetorhinus maximus) Sims et al., 2000]. ...
... Research is further hindered by sharks and rays being inherently elusive, precluding the use of classical study approaches to examine their social behavior using direct observation (Brena et al., 2018), resulting in a lack of information about their behavior. Temporary aggregations competing over limited resources (e.g., food), however, provide unique opportunities to gain insights into their inter-and intra-specific interactions (Dudley et al., 2000;Dicken, 2008;Clua et al., 2013), which can be characterized through a heterarchical framework (e.g., Brena et al., 2018). The provisioning of sharks and rays by humans, which is common in elasmobranch "eco-tourism, " has afforded tractable avenues to study sociality in these species (Newsome et al., 2004;Sperone et al., 2010;Maljković and Côté, 2011). ...
... Dominance measures and social network construction were based on dyadic agonistic interactions. An ethogram of dyadic agonistic interactions (Figure 2) was compiled based on prior observations of the sampled population and ethograms available for ray (Furst, 2011) and shark species (Clua et al., 2010(Clua et al., , 2013Sperone et al., 2010). We tested the ethogram over 2 days of observation prior to the study to ensure it was comprehensive. ...
Article
Full-text available
The advent of new technologies and statistical analyses has provided valuable insights into chondrichthyan social behavior. It has become apparent that sharks and rays lead more complex social lives than previously believed. Heterarchy combines hierarchy and social network theory and although it is not a new concept, it is rarely applied to animal social interactions. Here, we applied heterarchy to a case study involving smooth stingrays foraging for fish scraps at boat ramp in Jervis Bay, NSW Australia. We took advantage of their attraction to this site to examine their social behavior during agonistic interactions over the provisioned resource. We observed a stable, relatively linear but shallow dominance hierarchy that was highly transitive dominated by a single individual. Social network analysis revealed a non-random social network centered on the dominant individual. Contrary to previous research, size did not predict dominance, but it was correlated with network centrality. The factors determining dominance of lower ranks were difficult to discern, which is characteristic of despotic societies. This study provides the first heterarchical assessment of stingray sociality, and suggests this species is capable of complex social behavior. Given higher dominance and centrality relate to greater access to the provisioned resource, the observed social structure likely has fitness implications.
... Scavenging by sharks is relatively common, and likely an important component of their feeding ecology (Barnett et al. 2012;Fallows et al. 2013;Hammerschlag et al. 2016). A number of whale carcass scavenging events by sharks, mainly white (Carcharodon carcharias) and tiger sharks, have been documented (e.g., Long and Jones 1996;Dudley et al. 2000;Dicken 2008;Clua et al. 2013;Fallows et al. 2013). Apart from highlighting the importance of whale carcasses to shark diets, these opportunistic studies also revealed information on shark behavior. ...
... Dudley et al. (2000) observed both tiger and white sharks feeding concurrently on a whale carcass, with no competition or aggression observed between the two shark species or between tiger shark individuals; conversely, white sharks showed some intra-specific antagonistic behavior. Clua et al. (2013) identified at least 46 individual tiger sharks feeding on a blue whale (Balaenoptera musculus) carcass over 8 days. A size-based dominance hierarchy was observed, but with an increased tolerance toward smaller animals over time. ...
Article
Full-text available
Scavenging is an important component to the overall ecology of consumers in virtually all ecosystems on Earth. Given the energetic benefits of foraging on these resource subsidies, opportunistic predators will adjust their behaviors accordingly to maximize access. One of the many consequences of large-scale scavenging opportunities is species interactions that are rarely observed in nature. Here we describe the first published record of predatory sharks (tiger sharks, Galeocerdo cuvier) and saltwater crocodiles (Crocodylus porosus) foraging together in space and time, as documented on a large whale carcass off Western Australia. We report on and discuss the behaviors of the sharks and crocodiles in the hope of shedding new light on the interactions between apex predators that are rarely seen together, but may overlap under specific contexts.
... Although solitary sharks might occasionally gather around a common food source (e.g. whale carcasses, see [49]), we caution that the artificial aggregations described in this study do not reflect situations that commonly occur in the wild. Still, we accept as a core idea that the ability to assess peers through social information is beneficial in all contexts where individuals gather and interact with one another (see [50] for an example). ...
... Here, shark segregation by body size, albeit statistically significant, was of very limited magnitude. Contrary to previous findings [49,52,53], shark assortment by sex was also insignificant. Moreover, sharks established relatively stable dominance relationships that were related neither to size nor to sex. ...
Article
Full-text available
To adapt to their environment, organisms can either directly interact with their surroundings or use social information, namely information provided by neighbouring individuals. Social information relates to the external features of surrounding peers, and little is known about its use by solitary species. Here, we investigated the use of social cues in a solitary marine predator by creating artificial aggregations of free-ranging sicklefin lemon sharks (Negaprion acutidens). Using a novel monitoring protocol, we analysed both dominance interactions and tolerance associations between sharks competing for food in relation with the number, the morphology and the behaviour of rivals. Sharks produced more agonistic displays and spent more time around the bait as competitors were more abundant. Moreover, the morphological attributes of competitors had very limited influence on the structure of shark social interactions. Instead, sharks appeared to establish tolerance relationships with competitors according to their individual behaviour. Furthermore, the more two sharks were observed together at a given study site, the fewer agonistic interactions they exchanged. We discuss these findings as evidence of the use of social cues in a non-gregarious predatory species and suggest directions for future research.
... Adult tiger sharks possess heavily calcified, broad jaws that yield double serrated, cockscomb-shaped teeth, typifying the cutting tooth morphology (Cappetta, 2012). In combination with the lateral side-to-side movement of the head and body (saw-biting technique sensu Clua et al., 2013), these teeth allow them to even cut through hard tissues like the bony carapace of large sea turtles (Randall, 1992). In combination with their tremendous size of up to 5.5 m (total length) (Holmes et al., 2012) and their broad jaws, their specialized teeth allow tiger sharks to prey on a wide variety of different prey items, including cephalopods, teleosts, marine reptiles, sea birds and other elasmobranchs, but also indigestible anthropogenic objects such as cans, plastic bags, small barrels, pieces of metal, etc. (Compagno, 1984;Gudger, 1949;Randall, 1992). ...
... The weakly pronounced monognathic and dignathic heterodonty in tiger sharks has probably evolved as a specialization to facilitate the shark's ability to capture and handle large prey. Together with the characteristic cockscomb-shaped tooth morphology and the lateral side-to-side movement of the head (Clua et al., 2013;Randall, 1992), the tiger shark dentition functions like a saw and, therefore, allows it to easily cut through even the largest and hardest prey (e.g. sea turtles). ...
Article
Full-text available
The lifelong tooth replacement in elasmobranch fishes (sharks, rays and skates) has led to the assemblage of a great number of teeth from fossil and extant species, rendering tooth morphology an important character for taxonomic descriptions, analysing phylogenetic interrelationships and deciphering their evolutionary history (e.g. origination, divergence, extinction). Heterodonty (exhibition of different tooth morphologies) occurs in most elasmobranch species and has proven to be one of the main challenges for these analyses. Although numerous shark species are discovered and described every year, detailed descriptions of tooth morphologies and heterodonty patterns are lacking or are only insufficiently known for most species. Here, we use landmark-based 2D geometric morphometrics on teeth of the tiger shark Galeocerdo cuvier to analyse and describe dental heterodonties among four different ontogenetic stages ranging from embryo to adult. Our results reveal rather gradual and subtle ontogenetic shape changes, mostly characterized by increasing size and complexity of the teeth. We furthermore provide the first comprehensive description of embryonic dental morphologies in tiger sharks. Also, tooth shapes of tiger sharks in different ontogenetic stages are reassessed and depicted in detail. Finally, multiple cases of tooth file reversal are described. This study, therefore, contributes to our knowledge of dental traits across ontogeny in the extant tiger shark G. cuvier and provides a base-line for further morphological and genetic studies on the dental variation in sharks. Therefore, it has the potential to assist elucidating the underlying developmental and evolutionary processes behind the vast dental diversity observed in elasmobranch fishes today and in deep time. K E Y W O R D S elasmobranch, embryonic dentition, geometric morphometrics, ontogenetic trajectory, teeth, tooth pattern reversal
... Multi-species aggregations can lead to inter-specific interactions in the form of bites, chases and other forms of aggression, as has been reported between eagle rays (Myliobatis australis) and southern stingrays (Newsome et al. 2004). Individuals are likely to display dominance signaling in the presence of competitors, as agonistic interactions constitute an important factor in hierarchy establishment (Martin 2007, Clua et al. 2013. Group hierarchies described in fed elasmobranch aggregations are thought to be size-dependent (Newsome et al. 2004, Clua et competition related to food and reproduction is also discussed in the case of sicklefin lemon sharks in French Polynesia (Clua et al. 2010a) and southern stingrays in the Caribbean (Semeniuk & Rothley 2008) to explain the rise in seasonal intraspecific agonistic behaviors. ...
Article
Full-text available
The use of olfactory stimuli and the provision of food are a common practice to prompt artificial aggregations of emblematic wild species and ensure the economic viability of the wildlife-watching industry. Several elasmobranch species have been targeted by such operations in a variety of locations for over four decades. A recent review succinctly addressed the potential effects of shark diving tourism, including shark provisioning, on shark individual behavior and ecology, but the general paucity of data on the ecology of elasmobranchs precluded general statements. By using a functional framework, we reviewed the findings of the 22 available studies that investigated the behavioral, physiological, and ecological response of 14 shark and three ray species targeted by artificial provisioning. Focusing on the underlying processes that rule the response of targeted elasmobranch species, we report further effects acting beyond the individual-scale and their cross-scale relationships. We suggest that the most commonly described alterations of individual movement patterns have cascading effects through the group and community-scale, ultimately resulting in altered health condition and individual behavior toward humans. We conclude by stressing the potential for provisioning activities to support the investigation of complex ecological and behavioral processes in elasmobranchs.
... Many studies on predatory and/or scavenging behavior of large sharks are based on the analysis of bites and teeth marks left on dead floating or washed ashore cetacean and turtle's carcasses (Bornatowski et al. 2012a) or on behavioral observations of white sharks, Carcharodon carcharias (Linnaeus, 1758) and tiger sharks, Galeocerdo cuvier (Peron & LeSueur, 1822) feeding on cetacean carcasses (e.g. Bornatowski et al. 2012b, Taylor et al. 2012, Clua et al. 2013, Fallows et al. 2013). Studies focusing on interspecific or intraspecific elasmobranchs' feeding interactions are scarce, and the behavioral and kinematic aspects of this feeding activity remain almost unknown. ...
Article
Full-text available
The aim of this study is to report a scavenging event, involving the consumption of a nurse shark, Ginglymostoma cirratum, by tiger sharks, Galeocerdo cuvier, at Fernando de Noronha archipelago, Brazil. Recreational divers found and photographed a bitten nurse shark carcass, just after sighting two tiger sharks near of the site. We estimated the sharks total lengths and discussed aspects of this feeding interaction using of images of forensic analysis. A straight cut on the nurse shark caudal fin, whose total lenght was estimated as 200 cm, suggest that it was caught by illegal fishing. A skin peeling process on the nurse shark fins indicates that the tiger sharks consumed it after its death, in a scavenging event. This is the first published report of a scavenging event involving the consumption ofan elasmobranch by tiger sharks, allowing a better comprehension of tiger sharks’ alimentary biology.
... Towing a whale carcass out to sea poses logistical, legal and economic challenges, however, there are also a number of benefits. Large species of sharks, including White (Carcharodon carcharias) (Dicken, 2008;Fallows et al., 2013), Tiger (Galeocerdo cuvier) (Clua et al., 2013;Dudley et al., 2000), and Bull (Carcharhinus leucas) (Bornatowski et al., 2012), naturally scavenge the floating cetacean carcasses (Fig. 2C). The presence of these large scavengers allows for the recycling of carcasses to occur more rapidly than in a beach environment. ...
Article
The management of stranded whale carcasses is a logistical, environmental and economic challenge concerning a number of different stakeholders. In this paper, we review the current carcass disposal methods, stakeholders involved, and identify research needs and gaps. Examples of carcass disposals from all over the world are presented with Australia used as an example of current governance procedures and related challenges. Current management options include (1) leaving a carcass to decompose in situ, (2) beach burial, (3) oceanic tow, and (4) transport to waste management facility or rendering plant. Leaving a carcass to decompose in situ is the most cost effective and natural method, but raises issues of sight, smell, changes in sediment and groundwater chemistry, and shark attraction. Beach burials remove the sight and smell of a carcass and are relatively cost effective, but the extent to which carcass burial alters beach groundwater and attracts sharks to the surf due to leachate transported via submarine groundwater discharge is unknown. Oceanic tows are a simple disposal method, but carcasses can become boating hazards and may return ashore. Transporting carcasses to a waste management or rendering plant is costly, but effectively removes most social and environmental issues associated with a carcass stranding. The management of stranded carcasses involves a number of stakeholders with differing missions and priorities, from government agencies to conservation groups. Differences in priorities often cause tensions between groups increasing the complexity of carcass disposals. This review identifies key challenges and potential issues to guide decisions that are often made at a local scale. We recommend that clear legislation and organisational responsibilities are needed to prevent ambiguity when managing carcass disposal.
... In temperate and tropical waters, tiger sharks (Galeocerdo cuvier) are wide-ranging apex predators that undertake seasonal movements to actively hunt pulses of vulnerable terrestrial and marine prey (e.g., fledgling albatross, Phoebastria spp., Meyer et al. 2010). They have also been documented scavenging on whale carcasses e.g., (Dudley et al. 2000;Clua et al. 2013) and seabirds (e.g., Gallagher et al. 2011). ...
Article
Full-text available
The ability of predators to switch between hunting and scavenging (facultative scavenging) carries both short-term survival and long-term fitness advantages. However, the mechanistic basis for facultative scavenging remains poorly understood. The co-occurrence of tiger sharks (Galeocerdo cuvier) and green turtles (Chelonia mydas) at Raine Island (Australia), provides an opportunity to examine a top marine predator’s feeding mode in response to seasonal pulses in nesting turtles that offer both hunting and scavenging opportunities. Using satellite telemetry, we evaluated home range overlap between sharks and turtles and quantified their surfacing behavior around Raine Island during the turtle nesting season. We found core home range overlap to be highest during the nesting season. Both sharks and turtles spent significantly more time at the surface in areas of greatest range overlap closest to shore, where turtle density was highest. Both sharks and turtles showed decreased surfacing with increasing distance from Raine Island. Combined with published data on turtle demography at Raine Island, we propose the following: (1) sharks patrol the surface to increase scavenging opportunities on turtle carcasses and intercept weakened individuals after nesting; (2) healthy turtles may not perceive sharks as a major threat and/or other biological factors override anti-predatory responses; and (3) sharks during the nesting season may primarily scavenge on dead turtles individuals rather than actively hunt. Our study results and approach may be applicable to other situations in which direct observations of predator-prey interactions are limited. Significance Statement Every animal encounters dead or dying resources, yet the role of facultative scavenging has been difficult to study, and thus largely overlooked in marine behavioral ecological research. Movement analyses of tiger shark and green turtle movement and surfacing behavior at Raine Island (Australia) suggest that facultative scavenging may be a prevalent, yet underappreciated, feeding strategy in tiger sharks. Our integration of behavioral ecology theory with multi-species electronic tagging provided a valuable approach for investigating predator-prey interactions in situations where direct observations are limited or not possible.
... injury rate, compared to non-provisioned populations nearby (Semeniuk and Rothley, 2008 ). Most of these impacts have apparently not been investigated for many species. As a result, many impacts may go undetected . In other situations; however, the effects of provisioning are obvious. For example, provisioning may instigate 'feeding frenzies' (cf. Clua et al., 2013), with individuals aggressively competing, resulting in injury to other individuals (e.g., dolphins e Smith et al., 2008; sharks e Clua et al., 2010a; Dobson, 2006; Orams, 2002), or accidental beaching (e.g., stingrays and eaglerays e Newsome et al., 2004). To overcome the habituation observed in bottlenose dolphins in Shark Bay (Wester ...
... The tiger shark is also unique because it has highly kinetic jaws that are exceptionally broadbased, heavily calcified and fused at the symphyses [29]. This allows for the single row of cusped, serrated teeth to extend out from the skull, seize the prey and begin to saw into the bone, performing the 'saw-biting' technique [30]. The broad, heavily calcified jaws, supported by the extra-strong symphyseal fusion, reinforce the entire jaw apparatus and enable the shark to bite through very hard objects such as shells of chelonids [26]. ...
... Our finding is also consistent with the presence of tiger sharks in quite high densities in the coastal waters of New Caledonia. 6 The activity of kitesurfing has been recorded relatively rarely in reports of shark incidents in the short period since this sport commenced. Surfboard-riding and other surf sports have been the most common activities involved in unprovoked shark attacks for the past decade (often >50% in a particular year). ...
Article
We present a case of a non-provoked fatal shark attack on a 15-year old male kitesurfer in New Caledonia. The victim lost his board and was pulled by the sail along the water surface in a reef passage when a shark attacked. The shark inflicted at least two bites on the left leg, including a severe one around the knee, resulting in a quick hypovolemic shock that was fatal. The analysis of one of these bites indicated that a 2.8 m TL (est. length) tiger shark was responsible for this attack. The features of the attack are consistent with those of a predator response to a surface feeding stimulus.
... Previous studies suggest some occurrence of large bull sharks in Prony Bay. For example, Clua et al. (2013) observed adult bull sharks as the shark species responsible for the killing of an exhausted blue whale calf after entering this same area. Fishing efforts in the numerous rivers along the west coast of New Caledonia revealed several small juvenile bull sharks providing evidence that localised pupping occurs which is consistent with other studies showing female's return to rivers or estuaries, probably for pupping (Tillet et al. 2011;Werry et al. 2011). ...
Article
Conservation of threatened large sharks and management of shark-human interactions requires an understanding of shark occurrence and movement patterns. Here, we present the first catch, movement and behaviour data of adult bull sharks, Carcharhinus leucas, in New Caledonia. Amongst six adult C. leucas tagged with passive acoustic tags, four females were caught in coastal waters while males were only found at an isolated oceanic barrier coral reef over 100 km from the nearest river mouth. Two females were monitored in the southern New Caledonia lagoon for 707 and 208 days respectively and displayed classical transient behaviour and sporadic short-term residency around a coastal reef bay, with movements in and out a river detected prior to spring. Adult C. leucas in New Caledonia may develop a sex-based spatial segregation with an atypical presence of adult males in oceanic environments, probably influenced by the unique estuarine-marine continuum of the New Caledonian great lagoon.
... We fully agree with this description of the 'saw-biting technique', and we described that process during a scavenging event involving tiger sharks on the carcass of a Blue whale in New Caledonia. 7 However, that technique aims to remove large pieces of flesh and this hypothesis in the context of the Lifou case is quite inconsistent with the absence of loss of tissue on the victim. In addition, "sawing the femur", as suggested by Tirard et al., would oblige the shark to shake its head several times. ...
Article
Based on new photographs of the wound, Tirard et al. (2015) tried to demonstrate that the shark involved in a fatal attack on a human in Lifou in 2007 had homodont teeth and that it sawed the femur instead of directly cutting it, promoting the hypothesis that it was a tiger shark instead of a white shark. They also contested the data provided by the direct witness of the attack about the behaviour of the shark, specific to this former species. The evidences they provide are not convincing and, based on the absence of tissue loss and description of a jumping behaviour, we still believe that it was a single bite-and-spit attack by a white shark.
... This competition could induce physiological and behavioural responses that promote female dominance. In fact, the level of aggression has been observed as an important factor of dominance in female tiger sharks during feeding events (Clua et al., 2013), and therefore, it is plausible that competitive dominance could be related to the hormonal levels observed in the present study. As in males, testosterone can improve competitive abilities of females through mechanisms including enhanced muscle functioning and increased aggression (e.g. ...
Article
While a growing body of literature has shown that tourism provisioning can influence the behaviour of wildlife, how physiological state might be related to the nature and magnitude of these effects remains poorly understood. Physiological state, including reproductive and nutritional status, can have profound effects on an individual's behaviour and decision making. In the present study, we used multiple physiological markers related to reproductive (testosterone, 17β-oestradiol and progesterone), metabolic (corticosteroids) and nutritional ecology (stable isotopes and fatty acids), integrated with ultrasonography and passive acoustic telemetry to explore the possible relationship between physiological condition and space use of tiger sharks, Galeocerdo cuvier, exposed to dive tourism provisioning. Large, nongravid female tiger sharks, with higher plasma steroid levels (i.e. testosterone, 17β-oestradiol, relative corticosteroid), enriched δ¹⁵N and elevated nutritional status (in terms of fatty acids) spent proportionally more time at food provisioning sites compared to conspecifics. Testosterone levels also were positively correlated with the proportion of time spent at provisioning sites. Based on these results, we speculate that physiological condition plays a role in shaping the spatial behaviour of female tiger sharks within the context of food provisioning, whereby larger individuals, exhibiting higher testosterone levels and elevated nutritional status, show selective preferences for provisioning dive sites, where they outcompete conspecifics of relatively smaller size, lower testosterone levels and depressed nutritional state. While more studies are needed to explore whether sharks are making these decisions because of their physiological state or whether spending more time at provisioning sites results in altered physiological state, our findings highlight the importance of considering animal life stage, endocrine regulation, and nutritional condition when evaluating the biological impacts of provisioning tourism.
... Furthermore, the ferocity of the strikes by the oceanic whitetip shark, particularly those in association with ship wrecks and crashed airplanes, is usually exacerbated by the Bfeeding frenzy^of extremely aggressive competition among several sharks to feed on a common prey (Clua et al. 2013). When they initiate a feeding frenzy, the animals are in a sort of daze and act in absolute disorder, striking the victims, biting everything in proximity, metamorphosed into killing machines that are boosted by the smelling of large quantities of blood. ...
Article
Full-text available
Polynesians’ detailed observations of shark behaviour encompass the notion of a divinity, the fleeting image of a sky god, as well as potential source of food and valued tools. Due to prevailing cosmogony, sharks benefited from being a taboo species, historically limiting their exploitation. We examine how the reputedly fierce warriors of ‘Anaa (an atoll in Tuamotu archipelago, French Polynesia) came to be symbolically identified with a marine predator, being called “Parata,” the vernacular name of the oceanic whitetip shark Carcharinus longimanus. Both sharks and indigenous cultures are currently under threat in the East Pacific and we propose that an understanding of these sacred relationships could be used to help protect them.
... Stranded carcasses cause a number of known or perceived issues, including the unattractive sight and smell of decomposition, sediment and groundwater enrichment, and perceived shark attraction to the surf (Tucker et al., 2018). Potentially dangerous species of sharks such as White Sharks (Carcharodon carcharias) (Fallows et al., 2013) and Tiger Sharks (Galeocerdo cuvier) (Clua et al., 2013;Dudley et al., 2000) are attracted to, and scavenge, floating whale carcasses. This has created a perception that sharks may also be attracted to the near-shore area off beaches with buried carcasses due to the transport of leachate plumes via submarine groundwater discharge (Dower, 2016). ...
... Stranded carcasses cause a number of known or perceived issues, including the unattractive sight and smell of decomposition, sediment and groundwater enrichment, and perceived shark attraction to the surf (Tucker et al., 2018). Potentially dangerous species of sharks such as White Sharks (Carcharodon carcharias) (Fallows et al., 2013) and Tiger Sharks (Galeocerdo cuvier) (Clua et al., 2013;Dudley et al., 2000) are attracted to, and scavenge, floating whale carcasses. This has created a perception that sharks may also be attracted to the near-shore area off beaches with buried carcasses due to the transport of leachate plumes via submarine groundwater discharge (Dower, 2016). ...
Article
With the recovery of whale populations, carcass strandings on beaches are growing. Beach burial is a common management option for stranded carcasses. However, communities fear shark attraction following leachate transport to the ocean via submarine groundwater discharge. Here, a sediment column mesocosm experiment indicated that carcasses can be a localised source of dissolved organic carbon (DOC), phosphate and ammonium to groundwater. The spatial reach of the leachate plume was <2.5 m, while the temporal stabilisation occurred over 100–300 days. No significant chemical signals were observed under a beach-buried carcass, implying effective attenuation of decomposition plumes. For beaches with conditions similar to our one-directional, fast-flowing sediment experiment generating extreme groundwater contamination, it is unlikely that any leachate from a whale carcass would reach the ocean if buried >25 m onshore. Therefore, carcass leachate plumes would only potentially attract sharks to the surf under specific conditions not experienced during our experiments.
... It is also possible that some of these foraging behaviors may not have been focused on the potential prey species that were seen in the video, particularly in the case of benthic fishes. Facultative scavenging is an important feature of the behavior of tiger sharks (Clua et al., 2013;Hammerschlag et al., 2016) and in some cases sharks may have been drawn to approach mesopredatory benthic fishes simply by the potential opportunity to scavenge food, i.e., kleptoparasitism. This might explain why burst acceleration occurred only sporadically during prey investigations (Figure 4). ...
Article
Full-text available
An understanding of the role that large marine predators play in structuring trophic flow and nutrient cycling in marine ecosystems requires knowledge of their fine-scale (m-km) movement behaviors. In this study, biologging tags were used to reveal new insights into the three-dimensional fine-scale movement ecology of tiger sharks (Galeocerdo cuvier) at Ningaloo Reef, Western Australia. Tags deployed on 21 sharks in April-May 2017 for durations of 5-48 h recorded both physical parameters such as depth and temperature, and, through the use of accelerometers, gyroscopes and compasses, in-situ measurements of animal trajectory and locomotion. Animal-borne-video enabled the validation of behavioral signatures, mapping of habitat, and recording of interactions with prey. Collectively, these data were used to examine the link between vertical (oscillations) and horizontal (tortuosity) movements, and link sensor data to prey interactions recorded by the video. This biologging approach revealed complex movements that would otherwise be invisible within the time-depth records provided by traditional tagging techniques. The rate of horizontal turning was not related to vertical oscillations, suggesting that vertical movements occur independently of searching behaviors in tiger sharks. These animals displayed tortuous movements possibly associated with prey searching for 27% of their tracks, and interactions with prey elicited varied responses including highly tortuous paths and burst movements. Accurate speed measurements and GPS anchor points will considerably enhance the value of magnetometer data in future studies by facilitating more accurate dead-reckoning and geo-referencing of area-restricted search behaviors.
... Tiger sharks (Galeocerdo cuvier) are notorious for their dietary breadth. As predators, tiger sharks actively hunt prey including crustaceans, fishes, sea snakes, sea turtles, sea birds, and marine mammals (Castro 2010), but as facultative scavengers, they also supplement their diet by opportunistically scavenging items such as whale carcasses (Clua et al. 2013). Surprisingly, tiger sharks consume terrestrial birds as well. ...
... Sharks feeding underneath a whale can also be observed (depending on water clarity) which has not been possible in the past without the use of a shark cage that may influence behaviour. This gives researchers an additional view of an event and behaviours displayed, including some subtle communication behaviours sharks are known for [54]. Researchers are also able to pilot a drone from a distance that does not influence shark behaviour unlike traditional, handheld cameras which require an operator be close to a carcass. ...
Article
Full-text available
Over the past decade, drones have become a popular tool for wildlife management and research. Drones have shown significant value for animals that were often difficult or dangerous to study using traditional survey methods. In the past five years drone technology has become commonplace for shark research with their use above, and more recently, below the water helping to minimise knowledge gaps about these cryptic species. Drones have enhanced our understanding of shark behaviour and are critically important tools, not only due to the importance and conservation of the animals in the ecosystem, but to also help minimise dangerous encounters with humans. To provide some guidance for their future use in relation to sharks, this review provides an overview of how drones are currently used with critical context for shark monitoring. We show how drones have been used to fill knowledge gaps around fundamental shark behaviours or movements, social interactions, and predation across multiple species and scenarios. We further detail the advancement in technology across sensors, automation, and artificial intelligence that are improving our abilities in data collection and analysis and opening opportunities for shark-related beach safety. An investigation of the shark-based research potential for underwater drones (ROV/AUV) is also provided. Finally, this review provides baseline observations that have been pioneered for shark research and recommendations for how drones might be used to enhance our knowledge in the future.
... Historically, sharks have been perceived as solitary predators, however, according to recent studies, some species may exhibit both aggregation and social grouping (Clua et al., 2013;Bass et al., 2016). Moreover aggregation may well lay the important groundwork for the development of social groups (Sims et al., 2000). ...
Article
Full-text available
Provisioning activities in wildlife tourism often lead to short-term animal aggregations during the feeding events. However, the presence of groups does not necessarily mean that individuals interact among each other and form social networks. At the Shark Reef Marine Reserve in Fiji, several dozen bull sharks (Carcharhinus leucas) regularly visit a site, where direct feeding is conducted during tourism driven shark dives. On 3,063 shark feeding dives between 2003 and 2016, we visually confirmed the presence of 91 individual bull sharks based on external and long-lasting identification markings. We measured the intensity of associations between pairs of individuals by calculating the Simple Ratio Index (SRI) and calculated Generalized Affiliation Indices (GAIs) to distinguish true associations between dyads from structural predictor factors. Although the resulting mean SRIs were low, ranging from 0.01 to 0.12 (SRImean = 0.06; mean SRImax = 0.21), preferred long-term companionships were observed between individuals. Avoidances were also observed within pairs of individuals during the second half of the study. The best fitting model describing the temporal association patterns of bull sharks revealed a social structure which is characterized by preferred companionships and casual acquaintances. Our results suggest that the aggregation resulting from direct feeding has served to facilitate the development of social associations.
... Modern observations show that a single floating cetacean carcass may support a range of scavengers, including carcharhinids like bull and tiger sharks (Galeocerdo cuvier), and lamnids like shortfin makos (Isurus oxyrinchus) and great whites (Carcharodon carcharias), the latter being the closest living relatives of C. hastalis [72][73][74][75]. Tiger and bull sharks frequently target the blubber-rich throat region of extant mysticetes [75,76], with teeth occasionally getting stuck in the bitten items [73]. Similar behaviours may account for the high concentration of teeth associated with CLQM7, but fail to explain the absence of bite marks on the whale bones. ...
Article
Full-text available
The Miocene Pisco Formation, broadly exposed in the Ica Desert of southern Peru, is among the most outstanding Cenozoic marine Fossil-Lagerstätten worldwide. It is renowned for its exceptional preservation and abundance of vertebrate fossils, including a rich assemblage of whales and dolphins (Cetacea). Here, we integrate taphonomic data on 890 marine vertebrate fossils, gathered through 16 different localities. Our observations range from the taxonomic distribution, articulation, completeness, disposition and orientation of skeletons, to the presence of bite marks, associations with shark teeth and macroinvertebrates, bone and soft tissue preservation, and the formation of attendant carbonate concretions and sedimentary structures. We propose that the exceptional preservation characterising many Pisco vertebrates, as well as their exceptionally high abundance, cannot be ascribed to a single cause like high sedimentation rates (as proposed in the past), but rather to the interplay of several favourable factors including: (i) low levels of dissolved oxygen at the seafloor (with the intervention of seasonal anoxic events); (ii) the early onset of mineralisation processes like apatite dissolution/recrystallisation and carbonate mineral precipitation; (iii) rapid burial of carcasses in a soupy substrate and/or a novel mechanism involving scour induced self-burial; and (iv) original biological richness. Collectively, our observations provide a comprehensive overview of the taphonomic processes that shaped one of South America’s most important fossil deposits, and suggest a model for the formation of other marine vertebrate Fossil-Lagerstätten.
... Such negative interactions have already been observed for sicklefin lemon sharks (Negaprion acutidens) in another feeding site in Moorea, located on the outer reef, where some animals were displaying wounds inflicted during fights for dominance (Clua et al., 2010). Particularly strong dominance interactions could have occurred after reopening, but then progressively attenuated with time, allowing coexistence of different individuals in the same area of interest, as has already been shown for tiger sharks (Galeocerdo cuvier) around a blue whale carcass (Clua et al., 2013). ...
Article
The tourism activities linked to artificial provisioning of blacktip reef sharks (Carcharhinus melanopterus) and pink whiprays (Pateobatis fai) on a specific site in French Polynesia were suddenly and completely stopped due to a COVID-19 lockdown that lasted 6 weeks from March 20 until April 30, 2020. Using both drone footage and underwater counting, we were able to track the abundance of those two species before, during, and after reopening and thus investigate the impact of provisioning on wild shark populations. The absence of any stimulus during this long period resulted in almost total desertion of the site by the elasmobranchs. However, 1 day prior to reopening, some individuals of both species positively reacted to the single acoustic stimulus of an engine boat, showing the resilience of conditioning, and some elasmobranchs reacted to acoustic and olfactive stimuli linked to the provisioning practice from the first day after reopening. During the first 2 weeks after reopening, the abundance of both species remained at reduced levels comparable to those observed between 2008 and 2010 for sharks; i.e., around 9 animals in the presence of local tourists. Pre-lockdown abundance levels, reaching approximatively 15 individuals for sharks and 10 for rays, were considered restored 1 and 2 months after reopening for blacktip reef sharks and pink whiprays, respectively. These findings improve our capacity to better understand the potential effects of artificial provisioning tourism on the abundance of elasmobranchs by showing that conditioning is resilient for several weeks, suggesting that intermittent interruption of elasmobranchs feeding would not really help to decrease its impact on animal welfare.
... Recent stable isotope studies (Hussey et al., 2015b;Ferreira et al., 2017) confirm tiger sharks as apex predators but also that they are regionally and temporally adaptable and may function more as mesopredators in certain habitats (i.e., feeding on lower trophic level reef fishes, Ferreira et al., 2017). Additionally, there are observations of tiger sharks acting as facultative scavengers feeding at "bonanza" events such as whale carcasses Clua et al., 2013) and also examples of individuals that apparently target specific prey such as fledgling albatross (Lowe et al., 2006) and nesting sea turtles (Fitzpatrick et al., 2012). Thus, there are several aspects of feeding ecology that remain unknown including questions about the degree of individual feeding specialization (or generalization; Matich et al., 2011) and how these originate (e.g., through experience during ontogeny). ...
Article
Full-text available
This “Perspectives” paper identifies aspects of tiger shark (Galeocerdo cuvier) biology that are currently unknown or for which additional data are needed to improve interpretive power. Some of these data gaps may be regional. Technical or methodological approaches to acquiring these data are suggested. Some of these technologies already exist, some are in development and some exist in concept only. Reproductive biology and behavior, social interactions and the behavioral ecology of sub-adults are among the areas identified as deserving of future research effort.
Thesis
Full-text available
Aquatic highly migratory species (HMS) are economically and ecologically important, however, their highly migratory nature makes them difficult to study and thus there are knowledge gaps relating to their movement and habitat use patterns. Highly migratory sharks are likely to interact with commercial longline fishing gear and be caught as target or bycatch, which can threaten their populations. Understanding the environmental factors that influence and drive the movements of highly migratory sharks may help researchers better predict their presence and subsequently identify areas where they are vulnerability to fisheries. Here I evaluated the overlap between habitat suitability and gear restricted zones for three co-occurring apex predatory sharks in the Southwest Atlantic Ocean and Gulf of Mexico (great hammerhead Sphyrna mokarran, tiger Galeocerdo cuvier, and bull sharks Carcharhinus leucas) to identify areas in this region where these species are vulnerable to and protected from commercial longline fishing. This research was accomplished in three integrated steps. First, I reviewed and summarized what is known about the environmental drivers of great hammerhead, tiger, and bull shark habitat use and movement patterns. Second, I used the results of this review to parameterize and subsequently generate habitat suitability models for these three species. Third, I used these models to spatially compare where each species’ highly suitable habitat overlaps with longline gear restricted areas within the Southwest Atlantic Ocean and Gulf of Mexico, to identify regions where these species were both vulnerable to and protected from longline fishing gear. The results of this thesis have implications to the management of these species as well as for the conservation of other highly migratory aquatic species.
Article
Coastal managers are increasingly faced with the challenge of disposing of stranded whale carcasses on beaches. Direct burial in the beach is often used as a cost effective method of disposal. However, whale burial management plans are often met with public resistance owing to the perceived risk of shark attraction to burial leachate that may discharge from the seabed. A reactive transport model was combined with a numerical variable-density groundwater flow model to assess buried whale leachate plume formation, transport, influence on beach aquifer reactivity, and discharge to coastal surface water for a range of burial setback distances, depths, and whale sizes. A second set of simulations was performed to evaluate aquifer nitrate removal efficiencies for a range of buried wrack scenarios and to evaluate the role of organic carbon source on beach reactivity. A sensitivity analysis was performed for both sets of models across ten physical and reaction parameters. Simulations using the best estimate parameter set show that whale burials produce DOC and ammonium leachate plumes in the beach aquifer that are transported to and discharge near the low tide line in water depths of 0.4–2.4 m. DOC and ammonium concentrations in discharging whale leachate are 1.6 and 26 times higher than typical surf zone concentrations, respectively. Of the factors tested, the burial distance inland from the high tide line is the most important factor affecting leachate fluxes to surface water. Burials placed farther inland led to smaller DOC fluxes to surface water, but increased ammonium fluxes. Burial depth also affects whale leachate to the subtidal zone, with deeper burials resulting in smaller fluxes of DOC. Leached DOC from whale decomposition and from buried wrack can fuel denitrification hotspots within beach sediments. The sensitivity analysis showed that nitrate removal supported by buried wrack and whale leachate fluxes are highly dependent on beach properties, hydrologic forcing, and reaction parameters. The wrack model results have implications for beach scraping and the whale burial models show that whale leachate can be delivered to the shallow subtidal zone via groundwater discharge pathways, with potential implications for shark attraction and whale burial management practices.
Article
This study focuses on the important role of sharks in the Melanesian mythology. Based on unpublished stories essentially originating from New Caledonia, we show how strong the links are between myths and the physical environment in which Kanak live. As prevalent mythical animals, sharks can indifferently play the role of avengers and righters of wrongs, or vehicles for the spirits of living or dead people. They can be either allies or enemies in wars, and their role as potential man‐killers is never overlooked. However, when humans are attacked and killed by a shark, it is always for a material reason: the victim broke a rule or a tabu, the shark was an enemy, the sharks withdrew protection, the event allowed a pregnant woman to reach a new territory, etc. Beyond arbitrary metaphysical justifications, such perceptions reflect respect for social and natural order. For Kanak ni‐Vanuatu and other Pacific Islander peoples, sharks are part of a coherent Nature that includes natural and social hazards. In the quest for sustainable development of the planet, more in harmony with Nature, so‐called ‘developed societies’ might draw inspiration from such perceptions. Indigenous understandings could also help change the globally negative perception of sharks, and support shark conservation efforts in Oceania and worldwide.
Article
Full-text available
Tiger sharks, Galeocerdo cuvier , are a keystone, top-order predator that are assumed to engage in cost-efficient movement and foraging patterns. To investigate the extent to which oscillatory diving by tiger sharks conform to these patterns, we used a biologging approach to model their cost of transport. High-resolution biologging tags with tri-axial sensors were deployed on 21 tiger sharks at Ningaloo Reef for durations of 5–48 h. Using overall dynamic body acceleration as a proxy for energy expenditure, we modelled the cost of transport of oscillatory movements of varying geometries in both horizontal and vertical planes for tiger sharks. The cost of horizontal transport was minimized by descending at the smallest possible angle and ascending at an angle of 5–14°, meaning that vertical oscillations conserved energy compared to swimming at a level depth. The reduction of vertical travel costs occurred at steeper angles. The absolute dive angles of tiger sharks increased between inshore and offshore zones, presumably to reduce the cost of transport while continuously hunting for prey in both benthic and surface habitats. Oscillatory movements of tiger sharks conform to strategies of cost-efficient foraging, and shallow inshore habitats appear to be an important habitat for both hunting prey and conserving energy while travelling.
Data
Full-text available
This collection is the result of research in numerous journals, books and online publications. It contains 721 citations of papers about living/fossil sharks, rays and chimaeras (Chondrichtyes: Elasmobranchii, Holocephali) and a list of 2013 new described species and parasites of elasmobranchs.
Article
Full-text available
We present the results of a pilot study initiated during the fall of 2000 at the Point Reyes Headlands, a potential site for white shark research on the coast of California. The goal of this study was to determine if white sharks occur at this location. Ten sharks were observed during 45 h of sampling conducted between 9 October 2000, and 1 February 2001. Seven sharks were attracted to surface decoys deployed off of the headlands and three sharks were observed feeding on a whale carcass within Drake's Bay. No sharks responded to decoys presented within the Bay. Most sharks were observed early in the project, coincident with the presence of large numbers of young elephant seals.
Chapter
Full-text available
Several occurrences of White Sharks in tropical waters have been reported, but in the context of gaps in the knowledge of the ecology of that top predator, they appear as unusual and unexpected destinations. The New Caledonian exclusive economic zone covers 1,400,000 km 2 , with sea-surface temperatures oscillating between 20 and 21°C in winter and 28 and 32°C in summer. We have vali-dated fi fty-two sightings of White Sharks between 1943 and 2010, mainly based on professional fi shing bycatches and observations at sea. We obtained information on season in thirty-nine cases, shark size in forty-seven cases, and gender in twelve cases. To this, we added information for six different animals that were tagged with pop-up archival tags in New Zealand in April 2005 (two sharks) and March 2009 (four sharks), before releasing their tags in New Caledonian waters a few months later. Fifty-two percent of the animals were spotted in winter (July to September), 26% in spring (October to December), 23% in summer (January to March), and none in fall (April to June), which corresponds with the best season for tagging them in New Zealand. Thirty-two percent of the sharks were shorter than 3.8 m total length (TL), 45% between 3.8 and 4.4 m TL, 15% between 4.5 CONTENTS
Article
Full-text available
Two models to predict the food of predators are proposed. They assume that prey size and prey abundance are the only availability factors of importance to predators. One model assumes that the predator consumes prey as they are encountered and the other that predators feed to maximize their energy intake. Previous work, principally from aquatic situations is examined to test the models. It is concluded that many invertebrates and larval vertebrates eat prey as they are encountered while adult vertebrates feed as energy maximizers. The limitations of the models are discussed and their relation to models of optimal diet examined.
Article
Full-text available
Scavenging of marine mammal carcasses is thought to be an important part of the diet of white sharks (Carcharodon carcharias), though scientific observations of this behavior are rare. A detailed analysis of this feeding behavior has not been previously reported, nor has it been compared with the documented predatory feeding habits of this species. On 9 October 2000 we observed and photographed three white sharks scavenging on the carcass of a humpback whale (Megaptera novaeangliae) near Point Reyes, California. The sharks most often fed individually; however, simultaneous feeding by two white sharks was observed. The sharks targeted the outer blubber layer of the carcass, avoiding previously exposed muscle tissue. Ocular rotation and palatoquadrate protrusion, behaviors commonly associated with white shark predations, were not observed. The significance of these behaviors are discussed and contrasted with the reported predatory feeding behaviors of this species.
Article
Full-text available
The impact of fishing on chondrichthyan stocks around the world is currently the focus of considerable international concern. Most chondrichthyan populations are of low productivity relative to teleost fishes, a consequence of their different life-history strategies. This is reflected in the poor record of sustainability of target shark fisheries. Most sharks and some batoids are predators at, or near, the top of marine food webs. The effects of fishing are examined at the single-species level and through trophic interactions. We summarize the status of chondrichthyan fisheries from around the world. Some 50% of the estimated global catch of chondrichthyans is taken as by-catch, does not appear in official fishery statistics, and is almost totally unmanaged. When taken as by-catch, they are often subjected to high fishing mortality directed at teleost target species. Consequently, some skates, sawfish, and deep-water dogfish have been virtually extirpated From large regions. Some chondrichthyans are more resilient to fishing and we examine predictions on the vulnerability of different species based on their life-history and population parameters. At the species level, fishing may alter size structure and population parameters in response to changes in species abundance. We review the evidence for such density-dependent change. Fishing can affect trophic interactions and we examine cases of apparent species replacement and shifts in community composition. Sharks and rays learn to associate trawlers with food and feeding on discards may increase their populations. Using ECOSIM, we make some predictions about the long-term response of ecosystems to fishing on sharks. Three different environments are analysed: a tropical shelf ecosystem in Venezuela, a Hawaiian coral reef ecosystem, and a North Pacific oceanic ecosystem. (C) 2000 International Council for the Exploration of the Sea.
Article
Full-text available
Little is known about the long-term movement patterns of most marine apex predators. A network of acoustic receivers was used to quantify the long-term movements of transmitter-equipped tiger sharks Galeocerdo cuvier Peron & Lesueur, 1822 in the Main Hawaiian Islands. Tiger sharks were wide-ranging, swam between islands and patrolled up to 109 km of contiguous coastline. Visits to specific acoustic receiver sites were typically brief (mean duration 3.3 min), unpredictable and interspersed by absences of weeks, months or years. This pattern may be an optimal foraging strategy for capturing risk-averse prey. Tiger sharks may have to move on soon after arriving in an area because the element of surprise is quickly lost and potential prey become wary and difficult to catch. Juvenile tiger sharks were significantly wider-ranging and less frequently detected than mature females. Juveniles may be avoiding predation by larger individuals, or exploring to find suitable home ranges. Tiger sharks may also switch movement patterns and foraging strategies to take advantage of different prey types, restricting their movements to exploit seasonally abundant and naive prey. Further empirical studies are required to directly link movement patterns with foraging.
Article
Full-text available
The expanding use of digital photography for marine mammal photo-identification has created a need for tools to analyze and manage growing image file archives. While database management systems have been commonly employed to manage text and numerical data generated by photo-iden-tification research, their use for the analysis and management of associated image files has been limited. This paper describes a photo-identifica-tion database management system with embed-ded image analysis and management capabilities. Matching and cataloging are expedited using a multiple-attribute, non-metric catalog sorting algorithm. Algorithm efficiency at locating cata-log matches for bottlenose dolphins was compared to the performance of a more traditional single-attribute, non-metric approach. Locating catalog matches under the multiple-attribute approach required at least 50% fewer comparisons for 90% of the 409 individuals tested. For 50% of the indi-viduals, 80% fewer comparisons were required. System utility is further extended through embed-ded mapping components that allow researchers to visually inspect sighting locations following each survey and to examine sighting histories for specific individuals. In addition, a companion ArcGIS ™ extension allows researchers to quickly explore and interact with the photo-identification data within a GIS environment. This system, while created for a bottlenose dolphin research applica-tion, can be adapted to accommodate photo-iden-tification research on a variety of other species.
Article
Full-text available
A computer program named 'Finscan' was developed for identifying individual marine animals by comparing new photographic images with a collection of previously identii ed images. The matching process was based on the pattern of nicks and notches commonly found along the trailing edge of the dorsal n of many delphinid species. The program also allowed the inclusion of other user-dee ned descriptive features, such as leading-edge notches and truncated or irregular shapes. The output of the system was a presentation of images selected from the database, shown in order of similarity to a query image, so that the user could con rm the match. Two algorithms for representing notch patterns were tested and compared and the system was evaluated with dorsal n images of several marine vertebrates, as well as uke images for one species. Using a database of images that were previously identii ed by expert observers, the performance of the system was measured in terms of the number of incorrect matches that were oVered before the correct match. Since in most cases the correct match was oVered as the rst or one of the rst suggestions , the program substantially reduced the amount of eVort required to perform photo-based matching.
Article
Full-text available
1. There has been considerable debate over the past decade with respect to wildlife provisioning, especially resultant behavioural changes that may impact the ecological function of an apex predator. The controversy is exemplified by the shark diving industry, where major criticisms based on inference, anecdote and opinion stem from concerns of potential behaviourally mediated ecosystem effects because of ecotourism provisioning (aka‘chumming’ or feeding). 2. There is a general lack of empirical evidence to refute or support associated claims. The few studies that have investigated the behavioural impacts of shark provisioning ecotourism have generated conflicting conclusions, where the confidence in such results may suffer from a narrow spatial and temporal focus given the highly mobile nature of these predators. There is need for studies that examine the potential behavioural consequences of provisioning over ecologically relevant spatial and temporal scales. 3. To advance this debate, we conducted the first satellite telemetry study and movement analysis to explicitly examine the long-range migrations and habitat utilization of tiger sharks (Galeocerdo cuvier) originating in the Bahamas and Florida, two areas that differ significantly with regards to the presence/absence of provisioning ecotourism. 4. Satellite telemetry data rejected the behaviourally mediated effects of provisioning ecotourism at large spatial and temporal scales. In contrast, to the restricted activity space and movement that were hypothesized, geolocation data evidenced previously unknown long-distance migrations and habitat use for both tiger shark populations closely associated with areas of high biological productivity in the Gulf Stream and subtropical western Atlantic Ocean. We speculate that these areas are likely critically important for G. cuvier feeding forays and parturition. 5. We concluded that, in the light of potential conservation and public awareness benefits of ecotourism provisioning, this practice should not be dismissed out of hand by managers. Given the pressing need for improved understanding of the functional ecology of apex predators relative to human disturbance, empirical studies of different species sensitivities to disturbance should be used to guide best-practice ecotourism policies that maximize conservation goals.
Article
Full-text available
The results of a double-marking experiment using natural markings and microsatellite genetic markers to identify humpback whales (Megaptera novaeangliae) confirm that natural markings are a reliable means of identifying individuals on a large scale. Of 1410 instances of double tagging, there were 414 resightings. No false positive and 14 false negative errors were identified. The rate of error increased with decreasing photographic quality; no errors were observed among photographs of the highest quality rating, whereas an error rate of 0.125 was identified in sightings for which only part of the area used for identification was visible. There was also a weaker relationship between error rate and the distinctiveness of markings, which may result from non-independence in coding for image quality and distinctiveness. A correction is developed for the Petersen two-sample abundance estimator to account for false negative errors in identification, and a parametric bootstrap procedure for estimation of variance is also developed. In application to abundance estimates from the North Atlantic, the correction reduces the bias in estimates made using poorer quality photographs to a negligible level while maintaining comparable precision.
Article
Full-text available
In an initial telemetry study we examined patterns of activity and space-utilization by the lemon shark, Negaprion brevirostris, using manual ultrasonic tracking. Nine sharks were tracked intermittently for periods of 1-8 days: The longest continuous tracking segment lasted 101 h. Total activity space per individual ranged from 9-93 km2, as determined by the maximum-area polygon method. All sharks tracked at Bimini showed some degree of site attachment. The two largest sharks tracked elsewhere, did not remain in the area of tagging but made deepwater excursions. At Bimini, sharks tracked during the day were located eastward of their nighttime activity spaces. They moved westward over the flats at sunset and back eastward at sunrise. These sharks appeared to use the sun as an orientation cue. The tracks of two sharks fitted with speed-sensing transmitters demonstrated that swimming speeds were two times faster than the corresponding point-to-point rates of movement. The highest rates of movement were recorded at evening and morning twilight periods: the average nighttime rate was higher than the daytime rate—although statistical significance could not be established. Underwater and aerial observations showed lemon sharks to be associated with each other, with other sharks and with teleosts. Findings are interpreted in light of current information on space utilization, diel activity, social grouping, and energetics.
Article
Full-text available
Summary • The formulation of conservation policy relies heavily on demographic, biological and ecological knowledge that is often elusive for threatened species. Essential estimates of abundance, survival and life-history parameters are accessible through mark and recapture studies given a sufficiently large sample. Photographic identification of individuals is an established mark and recapture technique, but its full potential has rarely been exploited because of the unmanageable task of making visual identifications in large data sets. • We describe a novel technique for identifying individual whale sharks Rhincodon typus through numerical pattern matching of their natural surface ‘spot’ colourations. Together with scarring and other markers, spot patterns captured in photographs of whale shark flanks have been used, in the past, to make identifications by eye. We have automated this process by adapting a computer algorithm originally developed in astronomy for the comparison of star patterns in images of the night sky. • In tests using a set of previously identified shark images, our method correctly matched pairs exhibiting the same pattern in more than 90% of cases. From a larger library of previously unidentified images, it has to date produced more than 100 new matches. Our technique is robust in that the incidence of false positives is low, while failure to match images of the same shark is predominantly attributable to foreshortening in photographs obtained at oblique angles of more than 30°. • We describe our implementation of the pattern-matching algorithm, estimates of its efficacy, its incorporation into the new ECOCEAN Whale Shark Photo-identification Library, and prospects for its further refinement. We also comment on the biological and conservation implications of the capability of identifying individual sharks across wide geographical and temporal spans. • Synthesis and applications. An automated photo-identification technique has been developed that allows for efficient ‘virtual tagging’ of spotted animals. The pattern-matching software has been implemented within a Web-based library created for the management of generic encounter photographs and derived data. The combined capabilities have demonstrated the reliability of whale shark spot patterns for long-term identifications, and promise new ecological insights. Extension of the technique to other species is anticipated, with attendant benefits to management and conservation through improved understanding of life histories, population trends and migration routes, as well as ecological factors such as exploitation impact and the effectiveness of wildlife reserves. Journal of Applied Ecology (2005) doi: 10.1111/j.1365-2664.2005.01117.x
Article
Full-text available
Summary • The ability to identify individual animals is a critical aid in wildlife and conservation studies requiring information on behaviour, distribution, habitat use, population and life-history parameters. We present a computer-aided photo-identification technique that relies on natural marks to identify individuals of Carcharias taurus, a shark species that is critically endangered off the eastern Australian coast and considered globally vulnerable. The technique could potentially be applied to a range of species of similar form and bearing natural marks. • The use of natural marks for photo-identification is a non-invasive technique for identifying individual animals. As photo-identification databases grow larger, and their implementation spans several years, the historically used visual-matching processes lose accuracy and speed. A computerized pattern-matching system that requires initial user interaction to select the key features aids researchers by considerably reducing the time needed for identification of individuals. • Our method uses a two-dimensional affine transformation to compare two individuals in a commonly defined reference space. The methodology was developed using a database of 221 individually identifiable sharks that were photographically marked and rephotographed over 9 years, demonstrating both the efficacy of the technique and that the natural pigment marks of C. taurus are a reliable means of tracking individuals over several years. • Synthesis and applications. The identification of individual animals that are naturally marked with spots or similar patterns is achieved with an interactive pattern-matching system that uses an affine transformation to compare selected points in a single-user computer-aided interface. Our technique has been used successfully on C. taurus and we believe the methodology can be applied to other species of a similar form that have natural marks or patterns. The identification of individuals allows accurate tracking of their movements and distribution, and contributes to better population estimates for improved wildlife management and conservation planning. Journal of Applied Ecology (2007) 44, 273–280 doi: 10.1111/j.1365-2664.2006.01273.x
Article
Full-text available
Sharks as a group have a long history as highly successful predatory fishes. Although, the number of recent studies on their diet, feeding behavior, feeding mechanism, and mechanics have increased, many areas still require additional investigation. Dietary studies of sharks are generally more abundant than those on feeding activity patterns, and most of the studies are confined to relatively few species, many being carcharhiniform sharks. These studies reveal that sharks are generally asynchronous opportunistic feeders on the most abundant prey item, which are primarily other fishes. Studies of natural feeding behavior are few and many observations of feeding behavior are based on anecdotal reports. To capture their prey sharks either ram, suction, bite, filter, or use a combination of these behaviors. Foraging may be solitary or aggregate, and while cooperative foraging has been hypothesized it has not been conclusively demonstrated. Studies on the anatomy of the feeding mechanism are abundant and thorough, and far exceed the number of functional studies. Many of these studies have investigated the functional role of morphological features such as the protrusible upper jaw, but only recently have we begun to interpret the mechanics of the feeding apparatus and how it affects feeding behavior. Teeth are represented in the fossil record and are readily available in extant sharks. Therefore much is known about their morphology but again functional studies are primarily theoretical and await experimental analysis. Recent mechanistic approaches to the study of prey capture have revealed that kinematic and motor patterns are conserved in many species and that the ability to modulate feeding behavior varies greatly among taxa. In addition, the relationship of jaw suspension to feeding behavior is not as clear as was once believed, and contrary to previous interpretations upper jaw protrusibility appears to be related to the morphology of the upper jaw-chondrocranial articulation rather than the type of jaw suspension. Finally, we propose a set of specific hypotheses including: (1) The functional specialization for suction feeding hypothesis that morphological and functional specialization for suction feeding has repeatedly arisen in numerous elasmobranch lineages, (2) The aquatic suction feeding functional convergence hypothesis that similar hydrodynamic constraints in bony fishes and sharks result in convergent morphological and functional specializations for suction feeding in both groups, (3) The feeding modulation hypothesis that suction capture events in sharks are more stereotyped and therefore less modulated compared to ram and bite capture events, and (4) The independence of jaw suspension and feeding behavior hypothesis whereby the traditional categorization of jaw suspension types in sharks is not a good predictor of jaw mobility and prey capture behavior. Together with a set of questions these hypotheses help to guide future research on the feeding biology of sharks.
Article
Full-text available
A systematic, reliable method for identifying white sharks, Carcharodon carcharias Linnaeus, from underwater photographs was developed and applied to examine site fidelity at Guadalupe Island, Mexico (29˚N, 118˚W). The most reliable features for repeat identification in multiple years were the pigment patterns on the gill flaps, pelvic fins, and caudal fins. Pigment patterns in all three regions were asymmetrical on the right and left sides making it necessary to photograph both sides to catalog each individual. However, once cataloged, an individual could be re-identified using a partial body image. Using this method, 73 individuals were identified between 2001 and 2005. Site fidelity was indicated through repeated annual sightings of individuals with 78% of the identified sharks observed over at least 2years. Males were found to arrive at Guadalupe Island as early as July and females in September. Peak abundances at the site occurred August–December. The sex ratio was not significantly different from unity in 2002, 2004, and 2005. This monitoring technique has shown Guadalupe Island to be an important white shark aggregation site in the eastern Pacific.
Article
Full-text available
Female scalloped hammerhead sharks move offshore at a smaller size than do males to form schools composed primarily of intermediate size female sharks. This movement results in smaller females feeding more on pelagic prey than do males and with greater predatory success. It is contended that this change in habitat causes females to grow more rapidly to reproductive size. Intermediate size females grow at a more rapid rate than males. Female scalloped hammerhead sharks mature at a size larger than males. For many elasmobranch species, females: (1) occupy a different habitat, (2) grow more rapidly prior to maturity and continue growth following maturation, (3) feed on different prey with increased feeding success, and (4) reproduce at a size larger than males. It is suggested that female segregation increases fitness, resulting in more rapid growth for the former sex. The females reach maturity at the larger size necessary to support embryonic young, yet similar age to males, matching the female reproductive lifetime to that of males.
Article
Full-text available
The tiger shark (Galeocerdo cuvier) is the largest shark in the family Carcharhinidae and the only carcharhinid with aplacental viviparous (ovoviviparous) reproduction. Despite its size and prevalence, many details of tiger shark reproductive biology are unknown. Size at maturity and litter size have been reported by several authors, but a lack of large numbers of pregnant females has made it difficult to determine gestation period, seasonality, and timing of the female reproductive cycle. Here we analyze data from shark control program fishing and incidental catches in Hawaii (n=318) to construct the most complete picture of tiger shark reproduction to date. Males reached maturity at approximately 292cm total length (TL) based on clasper calcification, whereas females matured between 330 and 345cm TL based on oviducal gland and uterus widths. Litter sizes ranged from 3 to 57 with a mean of 32.6 embryos per litter. Data from 23 litters from various months of the year indicate that tiger sharks are usually 80–90cm TL at birth, and that the gestation period is 15–16 months. Mating scars were observed in January–February and sperm is presumably stored for 4–5months until ovulation takes place in May–July. Gestation begins in June–July and pups are born in September–October of the following year. Our data suggest that female tiger sharks in Hawaii give birth only once every three years. This could have major implications for conservation and management of this species, as it suggests that tiger shark fecundity is 33% lower than previously thought. This could greatly reduce the ability of this species to rebound from fishing pressure.
Article
Behavioral activities of a colony of 10 bonnethead sharks, Sphyrna t. tiburo, held under semi-natural conditions, were examined over a period of six months. All sharks had attained, or were approaching, sexual maturity. Objectives of the study were to describe species-typical motor patterns and postures, to analyze the diurnality of patrolling activity and to characterize pattern(s) of organization underlying social interactions noted within the colony. Eighteen postures and patterns of movement were described, almost half of them having apparent social relevance. In specific instances, functional significance of a pattern was cautiously given. Patrolling activity appeared to have a diurnal rhythm, with a peak occurring in the late afternoon; smaller individuals were more erratic in their patrolling. Finally, a clear but subtle social organization, based on a straight-line, size-dependent, dominance hierarchy was found. Though position within the hierarchy was not determined by sex, data indicated that all individuals tended to shy away from larger males. Sexual differences in the performance of certain patterns of movement were also established.
Article
L'auteur a suivi le séjour de 3 semaines d'un juvenile mâle de baleine bleue Balenoptera musculus brevicauda qui s'est réfugié en janvier 2002 dans une baie du Sud de la Nouvelle-Calédonie où son état général s'est progressivement dégradé jusqu'à ce qu'il soit attaqué et tué par des requins bouledogues Carcharhinus leucas. Le cadavre de l'animal a été ensuite dévoré par une agrégation (> 40) de requins tigres Galeocerdo cuvier.
Article
Stomach contents from tiger sharks, Galeocerdo cuvier, caught on lines off the central coast of Western Australia were analysed to investigate variations in the diet due to sex, size and geographic location. Stomachs from 84 specimens contained food, while 26 had empty stomachs and 66 had regurgitated. Twelve prey groups were identified, the most common being turtles, sea snakes, teleost fishes, dugongs and sea birds. Dietary overlap was high between males and females. An ontogenetic shift was observed in the diet. Smaller prey (e.g. cephalopods, teleosts and sea snakes) were more common in small individuals, while the occurrence of larger prey (e.g. turtles, dugongs and elasmobranchs) increased with increasing shark size. Differences in the diet were observed between four regions along the central Western Australian coast. The ability to catch and consume large prey, prey availability, prey density, and prey profitability were identified as factors influencing the diet. The high level of occurrence of dugongs and turtles in the diet of G. cuvier, relative to their abundance, suggests that shark predation may play an important role in regulating populations of these species.
Article
The results of a double-marking experiment using natural markings and microsatellite genetic markers to identify humpback whales (Megaptera novaeangliae) confirm that natural markings are a reliable means of identifying individuals on a large scale. Of 1410 instances of double tagging, there were 414 resightings. No false positive and 14 false negative errors were identified. The rate of error increased with decreasing photographic quality; no errors were observed among photographs of the highest quality rating, whereas an error rate of 0.125 was identified in sightings for which only part of the area used for identification was visible. There was also a weaker relationship between error rate and the distinctiveness of markings, which may result from non-independence in coding for image quality and distinctiveness. A correction is developed for the Petersen two-sample abundance estimator to account for false negative errors in identification, and a parametric bootstrap procedure for estimation of variance is also developed. In application to abundance estimates from the North Atlantic, the correction reduces the bias in estimates made using poorer quality photographs to a negligible level while maintaining comparable precision.
Article
Fifty mating events in free-living nurse sharks (Ginglymostoma cirratum) were observed over a nine-day period in the Dry Tortugas island cluster in the Florida Keys. Four stages of mating were identified: precoupling, coupling, positioning and alignment, and insertion and copulation. Copulation was observed and filmed in four of the mating events. Seminal fluid released into the water was obtained following one copulation and showed the presence of free, nonpackaged sperm cells. At least 10 of the events involved multiple males attempting copulation with single females.
Article
Suitable long term species-specific catch rate and biological data are seldom available for large shark species, particularly where historical commercial logbook reporting has been poor. However, shark control programs can provide suitable data from gear that consistently fishes nearshore waters all year round. We present an analysis of the distribution of 4757 Galeocerdo cuvier caught in surface nets and on drumlines across 9 of the 10 locations of the Queensland Shark Control Program (QSCP) between 1993 and 2010. Standardised catch rates showed a significant decline (p < 0.0001) in southern Queensland locations for both gear types, which contrasts with studies at other locations where increases in tiger shark catch per unit effort (CPUE) have been reported. Significant temporal declines in the average size of tiger sharks occurred at four of the nine locations analysed (p < 0.05), which may be indicative of fishing reducing abundance in these areas. Given the long term nature of shark control programs along the Australian east coast, effects on local abundance should have been evident many years ago, which suggests that factors other than the effects of shark control programs have also contributed to the decline. While reductions in catch rate are consistent with a decline in tiger shark abundance, this interpretation should be made with caution, as the inter-annual CPUE varies considerably at most locations. Nevertheless, the overall downward trend, particularly in southern Queensland, indicates that current fishing pressures on the species may be unsustainable.
Article
Despite being a common apex-level predator on coral reefs throughout the tropical Indo-Pacific, surprisingly little is known about whitetip reef shark (Triaenodon obesus) movements and biology. This study used photo-identification from community-contributed photographs to reveal patterns in movements, reproductive biology, and fisheries interactions in this species that have not been previously revealed through more traditional methods. At least 178 individual sharks were identified, and 26 movements were observed. These included movement distances of up to 26.4 km, movement rates of up to 3.27 km/day (9.8 km in 3 days), and movements that required the transit of a 140 m deep channel. Other animals showed high philopatry, being re-sighted at the same locality on multiple occasions (up to 13 sightings for one individual) over periods of up to 7 years. Females showed higher philopatry than males and were more likely than males to be found at shallow (
Article
Between 1979 and 1982, 523 sharks representing four families and 13 species were examined from sport fishing catches off New South Wales. Additional catch data were available from records of the Sydney Game Fishing Club extending from 1953 to 1979. The species composition of sharks caught changes through the year, probably as a result of seasonal variations in water temperature. Prionace glauca and Isurus oxyrinchus are most abundant in the catches during the cooler months from May to November. Galeocerdo cuvieri, Carcharhinus brevipinna, C. longimanus, C. falciformis, C. limbatus and Sphyrna lewini are taken principally during the warmer months from December to April. The sex ratio of P. glauca and Sphyrna zygaena changes through the year due to a seasonal influx of gravid females. At least six of the species examined give birth off New South Wales and, apart from C. falciformis, all of these appear to have restricted breeding seasons. P. glauca and S. zygaena feed mainly on cephalopods and to a lesser extent on fish, I. Oxyrinchus principally on fish, and G. cuvieri mostly on fish, birds, unidentified mammals and cephalopods.
Article
We used photo-identification to produce estimates of population size and structure of whale sharks Rhincodon typus at Ningaloo Reef, Western Australia. We analysed photographs of whale sharks taken from 1992 to 2004. A combination of spot and stripe patterns behind the last gill slit and forward of the dorsal fin (lateral view), and distinctive scars and marks on the body and fins were useful for identifying individual sharks. These patterns appeared to be unique to individuals and distinctive markings could be recognized on some sharks for more than a decade. From 581 photographs, 159 individuals were identified. Of these, 74% were male, 16% were female and 10% were of indeterminate gender. Photographed sharks ranged in estimated size from 3 to 10 m total length (TL). The size distribution of sharks was bimodal with a large peak at 8 m and a smaller peak at 6 m TL. Sixty individuals were resighted during the study. Of these, 46 were resighted at different times during the same year (sometimes on multiple occasions) up to 4 mo after they were initially photographed, and 33 were resighted (4 on >2 occasions) in different years. The interval between inter-annual resightings was typically 1 to 3 yr; however, 2 sharks were resighted after a period of 12 yr. We estimated the super population of whale sharks that visit Ningaloo Reef to consist of approximately 300 to 500 individuals (95% confidence interval) based on closed population models, or 320 to 440 based on Jolly-Seber open-population models. Our study shows that photo-identification offers a practical, non-invasive and non-destructive means to obtain data on the population size and demography of whale sharks.
Article
Agonistic displays in 23 species of sharks of six families are described and illustrated. These displays are reviewed in terms of ethological concepts and shark hydrodynamic models. Shark agonistic displays feature many common elements rendering them readily distinguishable from normal swimming and pseudodisplays caused by sharksucker irritation. Shark agonistic displays are most readily elicited by rapid, direct diver approach when food is absent and potential escape routes restricted. Such displays appear to be motivated by defence of self or the immediately surrounding space rather than defence of territory or resources. Costs and benefits of display versus attack in shark–shark and shark–diver contests are evaluated using payoff matrices and optimal strategies are identified. Shark–human interactions are modelled in terms of a system of nested critical approach distances. For divers faced with a displaying shark, responses which may decrease the likelihood of defensive attack are suggested. Recommendations for future work on shark agonistic behaviour are offered.
Article
The biology of 835 specimens of Galeocerdo cuvier caught between 1964 and 1986 off Townsville, Australia, was examined. The sharks were caught in a protective meshing programme using both large mesh gill-nets and set lines. The size at birth was estimated to be 80-90 cm total length, and females matured at approximately 287 cm total length. Litter sizes ranged from 6 to 56. Breeding and pupping both appear to occur in summer, with females not breeding every year. Mature females possibly migrate inshore during late spring and summer to give birth. The sex ratio of juveniles and adults favoured females, with few adult males being caught. Ontogenic changes in the diet were observed, with juveniles feeding predominantly on teleosts, sea snakes and birds and adults mostly consuming teleosts, sea snakes, turtles and crabs. There was no apparent decrease in the population size of G. cuvier in the Townsville area as a result of the long-term catching of sharks by the protective meshing programme.
Article
Basking shark (Cetorhinus maximus) movement patterns and growth rates over annual cycles remain entirely unknown. Here the re-sighting of a female identified by a highly distinctive first dorsal fin, after a 3·1 year period is described. Our results show this individual foraged at the surface in coastal areas off south-west England in at least two of four summer seasons and increased in total length by 2·4 m over this period. The growth increment observed was similar to that predicted from the growth model for this species.
Article
Observations of great white sharks (Carcharodon carcharias) scavenging from cetacean carcasses are rare and have only been reported in the scientific literature for large (>3.5 m total length (TL)) individuals. Between 13 October and 25 November 2006, young of the year and juvenile great white sharks were observed scavenging from the carcass of a humpback whale (Megaptera novaeangliae) in Algoa Bay, South Africa. Although more than one shark scavenged from the carcass, simultaneous feeding was not observed. The sharks showed a clear preference for soft tissue at sites along the mouth of the carcass. Protective ocular rotation was rarely observed and none of the sharks exhibited palatoquadrate protrusion while feeding. These observations provide a new insight into the foraging behaviour of young of the year and juvenile great white sharks. The prevalence of small great white sharks (1.5 m TL) and the absence of any individuals greater than 3.65 m TL suggest that Algoa Bay may function as a nursery area for great white sharks in South Africa. This information is crucial not only to improve our understanding of great white shark biology, but also for their long-term management and conservation in South Africa.
Article
Sharks are marine consumers believed to occupy top positions in marine food webs. But surprisingly, trophic level estimates for these predators are almost non-existent. With the hope of helping better define the ecological role of sharks in marine communities, this paper presents standardized diet compositions and trophic levels calculated for a suite of species. Dietary composition for each species was derived from published quantitative studies using a weighted average index that takes into account sample size in each study. The trophic level (TL) values of the 11 food types used to characterize the diet (obtained from published accounts) were then used to calculate fractional trophic levels for 149 species representing eight orders and 23 families. Sharks as a group are tertiary consumers (TL>4), and significant differences were found among the six orders compared, which were attributable to differences between orectolobiforms (TL<4) and all other orders, and between hexanchiforms and both carcharhiniforms and squatiniforms. Among four families of carcharhiniform sharks, carcharhinids (TL=4.1, n=39) had a significantly higher TL than triakids (TL=3.8, n=19) and scyliorhinids (TL=3.9, n=21), but not sphyrnids (TL=3.9, n=6). When compared to trophic levels for other top predators of marine communities obtained from the literature, mean TL for sharks was significantly higher than for seabirds (n=28), but not for marine mammals (n=97). Trophic level and body size were positively correlated (r s =0.33), with the fit increasing (r s =0.41) when the three predominantly zooplanktivorous sharks were omitted, and especially when considering only carcharhinid sharks (r s =0.55).
Article
Shark feeding is a controversial recreational activity that may alter shark behaviour. In order to investigate possible behavioural changes at the level of the individual, it is necessary to recognise each shark underwater and in a nonintrusive way. In this study, we tested a protocol based on natural marks on fins, and coloured spots and scars on the body to differentiate individual sicklefin lemon sharks. We found that a feeding group, aggregated for 26 months at a northern location off Moorea Island, comprised 32 animals (19 females and 13 males), identified from 2589 observations made over 541 dives. Post-dive photo-identification of individual sharks was a reliable technique, whereas a high level of skill was required to ensure an instantaneous identification underwater. However, direct underwater identification of individual sharks can be of potential use in shark behavioural studies.
Article
The tagging of sharks using conventional tags has long been recognized as a valuable means for studying various aspects of their life history, migrations and movements, and population structure. Conventional tags are defined as those that can be identified visually without the use of special detection equipment. Tagging studies specifically targeting sharks began in the late 1920's, and today numerous cooperative shark tagging programs exist worldwide. Cooperative programs depend on the joint participation of scientists and public volunteers to accomplish research objectives. Benefits and problems of these programs are discussed using the tagging methodologies, protocols, and results of the National Marine Fisheries Service Cooperative Shark Tagging Program. An additional 63 shark tagging studies and programs of all types are reviewed. Information useful for behavioral, biological, and fishery management studies can be derived from data resulting from these studies, including species and size composition, sex ratios, spatial and temporal distribution, migrations, movement patterns, rates of travel, delineation of pupping grounds, distribution of maturity intervals, indices of relative abundance, and recognition of individuals. Specific tagging experiments can be designed to provide additional data on age and growth, homing and site fidelity, dispersal rate, residence time, movement rates, tag shedding, and population parameters (e.g. size, mortality, recruitment, exploitation, interaction rates, and stock identity). Sources of bias inherent in tagging and recapture data include mortality, variation in tagging effort and fishing pressure, non-recovery and non-reporting of tags, and tag shedding. Recent advances in tagging methodologies that complement and extend conventional tagging studies will further our knowledge on shark movements and migrations, particularly in the areas of resource utilization and management, space utilization, and population dynamics.
Article
Tiger sharks, Galeocerdo cuvier, are apex predators in a variety of nearshore ecosystems throughout the world. This study investigates the biology of tiger sharks in the shallow seagrass ecosystem of Shark Bay, Western Australia. Tiger sharks (n = 252) were the most commonly caught species (94%) compared to other large sharks. Tiger sharks ranged from 148–407cm TL. The overall sex ratio was biased towards females (1.8:1), but the sex ratio of mature animals (> 300cm TL) did not differ from 1:1. Contrary to previous accounts, tiger sharks were caught more often in all habitats during daylight hours than at night. Tiger shark catch rates were highly correlated with water temperature and were highest when water temperatures were above 19C. The seasonal abundance of tiger sharks is correlated to both water temperature and the occurrence of their main prey: sea snakes and dugongs, Dugong dugon. Stomach contents analysis indicated that sea turtles and smaller elasmobranchs were also common prey. The importance of major seagrass grazers (dugongs and green sea turtles, Chelonia mydas) in the diet of tiger sharks suggests the possibility that these sharks are keystone predators in this ecosystem.
Article
Despite the recent upsurge of interest in shark research, the current status of knowledge of the behavioural repertoire of most species is alarmingly incomplete. Clearly, from the steadily decreasing numbers of sharks caught by commercial and sport fishermen, sharks are highly vulnerable to human exploitation. Although education is making inroads, there is still steady opposition to the enforcement of catch limits and management strategies for most species. Accurate life history and behavioural information is required to enforce management policies. Wetherbee et al. (1990) cited a case in which commercial fishermen accused the spiny dogfish of stripping the commerical and recreational fisheries of their herring and salmon catch. A detailed study of the spiny dogfish diet disproved their claims. Sharks are clearly not mindless eating machines, as they have been labelled in the past. They are intelligent and have complex patterns of movement, space utilization, and social organization. Using a combination of remote and direct observational techniques, the scientific community is beginning to have a more complete understanding of these important apex predators in coral reef and oceanic ecosystems. More importantly, researchers who are interested in pursuing the fascinating field of shark behaviour still have a wide choice of direction.