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As ecotourists become increasingly interested in snorkeling and diving with sharks, it is important to establish directives for safe interactions. The study considered eye contact between humans an...

Eye contact with a shark is a crucial element during an interaction with a diver. Different mask frames change the size of a diver’s available field of vision, and so make a person’s eyes unequally visible from different angles, particularly when comparing mirrored to regular glass. This study examined whether it matters to a shark if it can see a diver’s eyes when getting closer. The test-subjects changed masks in a random, timed routine, while the relative distance, the absolute distance between a shark and diver expressed in a fraction of the shark’s body length, between approaching shark and human was tallied. Sharks came significantly closer (p = 0.0139) when a diver’s eyes could not be detected, showing that they orient themselves and approach based on the human’s eyes. Given that human comprehension of sharks is rudimentary, every possible benefit, even a minimal one like choosing the most optimal mask, is recommended whenever approaching sharks are likely to be encountered.

It is unknown if resting sharks can sleep, which is also true for gliding ones. Here, a videotaped bull shark is presented that drifted in an uncontrolled manner for 120 seconds while sinking with 0.1 m/second. Several aspects are discussed to determine if the shown behavior reflects the commonly accepted definition of sleep. Additionally, the idea is also discussed if this state might reflect a “quiet waking state” instead of where the shark still maintained some vigilance despite its general appearance.

Sharks and sharksuckers maintain a mutualistic symbiotic relationship; thus, it is surprising to observe a lemon shark, Negaprion brevirostris, killing a sharksucker, Echeneis lucrates, which has been recorded during a dive with lemon sharks. Does this observation indicate that the symbiosis between the two species may shift occasionally? The awkwardness of the recorded kill, combined with its comparatively long duration, suggests this bout be a freak incident, rather than a common occurrence; thus, the mutualistic relationship needs not be questioned. What triggered the bout, however, can only be speculated. Although the caloric value of the killed sharksucker is not known, a feeding-oriented behavior can likely be rejected as the potential cause based on the teleost’s rather small size, and an irritation related issue is more likely to have triggered this bout.

Background:Close-up videos of sharks foraging on other live sharks are rare, especially when it comes to footage of the entire duration of an event.Objective:Our goal was to present an in-depth analysis involving a Galapagos shark,Carcharhinus galapagensis, foraging on a whitetip reef shark,Triaenodon obesus.Method:A frame by frame video examination was used to highlight the different aspects of this bout.Results:Several behavioral characteristics, including the somewhat cryptic approach, the extensive shaking once the Galapagos shark had the whitetip reef shark between its jaws, and devouring tail-first, stand out in this event.Conclusion:The entire act appeared very smooth, indicating that this bout, or at least parts thereof, may represent a common hunting strategy for Galapagos sharks.

On rare occasions, during mating season among sharks, ‘mating scars’ appear on female sharks’ bodies caused by the males holding onto them. The low frequency of sharks bearing such scars indicates that those markers are not part of regular mating efforts. These scars are mostly deeper cuts and punctures, indicating a more forceful motivation such as coercive mating from the male’s side. We discuss scenarios based on mating scars from three Carcharhinid species, describe and explain the arrangement of these bite scars, and consider plausible mating strategies used by males, including coercive mating.

Feeding is the likely cause for tooth shedding in sharks. Although the overall process of loosing teeth has been well studied, hardly any emphasis has been given to the actual separation mechanism between a shark’s tooth base and the surrounding jaw tissue. Attention is given to this very process, in connection to a never before videotaped tooth loss of a white shark, Carcharodon carcharias, that occurred within 0.3 seconds. Since the shark did not bite into anything prior to this observation, the cause for this tooth loss does not seem feeding but fatigue related, triggered through a combination of mechanical and potentially biochemical degradation processes.

The coexistence between sharksuckers and sharks is poorly understood. Here, we studied the symbiotic client-cleaner relationship between Lemon Sharks, Negaprion brevirostris, and sharksuckers, Echeneis naucrates, with a focus on cleaning inside the sharks' mouths. Where observable, cleaning bouts were either initiated by a sharksucker moving along a shark's snout while maintaining body contact or by swimming in a “dance like” manner in front of the shark's eye without contact, until the shark gaped to allow entry. Sharksuckers interacting with sharks were typically in their first year of their life. While being cleaned by sharksuckers, Lemon Sharks were always seen in one of two positions: either lying flat on the sea floor, or propped on their pectoral fins. Cleaning bouts lasted significantly longer when the shark was propped. In bouts where the location of sharksucker activity within the mouth could be determined, cleaning activity exclusively occurred around the teeth of the upper jaws. In more than h...

The trends of the world’s top ten countries relating to shark bite rates, defined as the ratio of the annual number of shark bites of a country and its resident human population, were analyzed for the period 2000-2016. A nonparametric permutation-based methodology was used to determine whether the slope of the regression line of a country remained constant over time or whether so-called joinpoints, a core feature of the statistical software Joinpoint, occurred, at which the slope changes and a better fit could be obtained by applying a straight-line model. More than 90% of all shark bite incidents occurred along the US, Australia, South Africa, and New Zealand coasts. Since three of these coasts showed a negative trend when transformed into bite rates, the overall global trend is decreasing. Potential reasons for this decrease in shark bite rates—besides an increase in the world’s human population, resulting in more beach going people, and a decrease of sharks due to overfishing—are discussed.

Amin, R.; Ritter, E., and Wetzel, A., 2015. An estimation of shark-attack risk for the North and South Carolina coastline. A spatiotemporal cluster analysis of shark-attack rates is applied to identify coastal areas with shark-attack rates that are very high or very low along the North and South Carolina coast. Using a cluster analysis makes it possible to not just pinpoint these areas with more accuracy but also identify where incidents are unlikely to happen. In the past, shark attacks have been studied from a viewpoint of encounter number per region and so limited to the areas in which the attacks occurred. A first look is also taken of the potential influences of some anthropogenic, environmental, and meteorological factors for North and South Carolina in comparison with the better-known attack-prone areas along Florida's coast, to quantify potential causes leading to elevated shark-attack rates, or the lack of them.

The mouth of a shark is a breeding ground for a large variety of bacteria which can easily get transferred onto a human body in the event of a shark bite. Here, we review infections originating from shark oral bacterial flora, which originate from the microbiome of its prey, as well as from the surroundings where an incident takes place. We use the example of an incident which occurred in an aquarium involving a sandtiger shark, Carcharias taurus. In addition to a succinct analysis and interpretation of the wound and recovery process, an overview of currently known bacteria associated with shark bite wounds is given, as well as a summary of the effects of various previously tested antibiotics on bacteria derived from blacktip sharks, Carcharhinus limbatus, bull sharks, C. leucas, and tiger sharks, Galeocerdo cuvier. LEVEL OF EVIDENCE Therapeutic study, level V.

This study examines the approach patterns of sharks in the vicinity of human divers, focusing on the diver’s body orientation and a shark’s distance from the sea bed when approaching the diver. A standardized video method was used to record the scenario of diver(s) kneeling in the sand while being approached by sharks. This showed that sharks had a preference to move in from outside a diver’s field of vision while larger sharks stayed closer to the sea floor. This may simultaneously enhance camouflage while reducing potential escape routes for the approaching animal. This stealth behavior raises the question of how sharks may interpret humans when moving towards them.

Five unprovoked shark attacks are reported from Sharm-El-Sheikh, Egypt, between 30 November and 5 December 2010. Three of the five attacks are attributed to an oceanic whitetip shark, Carcharinus longimanus with a distinctive crescent-shaped notch in the upper lobe of the caudal fin. The shark was observed during the first attack on a snorkeler and photographed underwater during the second shark attack on a swimmer. In a video taken several months prior to the attacks, the same shark is hand-fed underwater by a divemaster with additional fish in a pack over his buttock. The shark can be seen swimming behind the divemaster while he removed additional fish from this pack. In Victims 1, 2 and 5, the shark removed an extensive amount of tissue from the victims’ buttock. The three victims also lost a hand and/or a portion of their forearm, suggesting the injuries were inflicted by a shark conditioned to associating food with hand-feedings and the human form. The remaining two attacks, Cases 3 and 4, were attributable to the shortfin mako shark, Isurus oxyrinchus. This was determined from a unique dental pattern of the right side of the upper jaw due to a prior injury. This same “misalignment” dental pattern was observed in the injuries sustained by Victims 3 and 4. We conclude that the shortfin mako shark was responsible for the attacks on Victims 3 and 4, and the oceanic whitetip shark was the causal species of attacks on Victims 1, 2, and 5.

One recurring factor seemingly causing an increase in shark attacks is lunar cycles, especially the full moon. However, the potential association between shark attacks and lunar cycles has never been verified. Our results show that a correlation between shark attacks and moon cycles does not statistically exist. With no correlation between shark attack rates―independent of people's activities―and lunar cycles found, we also applied the same statistical procedures to surfer incidents only. The reasoning for narrowing the attacks to those on surfers was as follows: (1) Surfers indicate the best conditions to surf exist during the full and new moon. (2) Surfers are more exposed to shark attacks than non-surfers. However, as with the initial results, shark attacks involving surfers did not show any correlation to lunar cycles, neither did those involving non-surfers. These results indicate that potential triggers for shark attacks need to be studied in a more pragmatic manner, using, for example, mathematic approaches to test for global phenomena and then individual instances, leaving guess work largely aside.

Shark attacks have historically been studied from a viewpoint of encounter number per region and so limited to the areas in which the attacks occurred. In this exploratory modeling study, the goal was to examine whether an area-specific cluster analysis algorithm undertaken with a modern cluster analysis tool (SaTScan™ 9.1.0) could enhance our spatial and spatio-temporal understanding of attack patterns. The data used were from Florida's east coast between 1994 and 2009. The program suggests several high- and low-risk areas for shark attacks. The results are discussed from a quantitative rather than qualitative perspective.

This study tested whether human body orientation can influence the behavior of bull sharks by examining sharks’ approach distances from a person positioned vertically or horizontally in the water. Results showed that bull sharks,Carcharhinus leucas, kept a significantly greater distance when the test subject was standing in chest-deep water with his head above water versus lying on the ocean floor. Furthermore, larger bull sharks in the immediate area withdrew when the subject entered the water.

Mouth gaping in sharks has been considered to be either a threat display or a response to sharksucker irritation, but has never been examined in greater detail. Another form of gaping was observed frequently around feeding scenarios, primarily when sharks swam away from the food source. This form of a yawn-like behavior of Caribbean reef sharks, Carcharhinus perezi, was videotaped during both standard feeding and non-feeding scenarios, and examined for both proximate causation and function. This type of gaping reflects a simulated bite process, including all bite phases, but differs from actual bites in that the duration is as great as 10 times longer, with the expansion phase disproportionally prolonged and a pause at the gape's peak. Of all the possible functions discussed, a maintenance behavior to reposition the jaw elements after feeding fits all of the measured parameters.

The theory of mistaken identity states that sharks, especially white sharks,Carcharodon carcharias, mistake surfers for pinnipeds when looking at them from below and thus bite them erroneously. Photographs of surfer wounds and board damage were interpreted with special emphasis on shark size, wound severity, and extent of damage to a board. These were compared with the concurrent literature on attack strategies of white sharks on pinnipeds and their outcomes. The results show that the majority of damage to surfers and their boards is at best superficial-to-moderate in nature and does not reflect the level of damage needed to immobilize or stun a pinniped. It is further shown that the size distribution of sharks biting surfers differs from that in pinnipeds. The results presented show that the theory of mistaken identity, where white sharks erroneously mistake surfers for pinnipeds, does not hold true and should be rejected.

Bite wounds on humans have rarely been comparatively analyzed, and the behavior leading to such bites is virtually unknown. Nevertheless, the behavior of a shark is reflected in the bite structure and should be an essential part of shark-accident analysis. This paper compares 3 nonfatal accidents on humans, caused by bull sharks, Carcharhinus leucas, that occurred within a 12-month period in the same area of the Bahamas. Examination focused on wound analysis and accident reconstruction to determine the most likely bite motivation of the sharks. Two sharks targeted the left calf areas of the victims; another one bit the back area of a person. Although both calf bites had a very similar appearance, examination concluded that one of them showed the same triggering behavior as for the shark who inflicted the very different-looking back bite. Those 2 bites were competitive, whereas the other calf bite was initially of exploratory nature, turning into a stress-related bite.

Sharks react in a variety of ways when sharksuckers attach to their bodies. Here, an unobserved behavior is de- scribed in which a blacktip shark, Carcharhinus limbatus, uses a pectoral fin in a scoop-like manner to specifically target the removal of a sharksucker, Echeneis naucrates, in the flank area. This coordinated use of the pectoral fin indicates an established bout in the shark's repertoire to remove sharksuckers. The anatomical flexibility and coordination of the fin is discussed; likewise, the potential origin and commonality within other species of the same family based on the rise of sharksuckers in the Eocene-Oligocene period. Special emphasis is placed on the value of a single observation of animal behavior in the field.

I analyzed and quantified the behavior of blacktip sharks, Carcharhinus limbatus, irritated by sharksuckers, Echeneis naucrates, attached to their bodies. The sharksucker induced behavior patterns were divided into simple rotational patterns, expressed by body turns along their main axes (roll, yaw, pitch); and complex patterns (wiggle, shake, wind, chafe), consisting of a combination or a repetition of simple behavior patterns. Three nonrotational behavior patterns were also observed (freeze, yawn, flicker). Of the 78 blacktip sharks examined, 70 performed either a simple or a complex pattern, or a combination of the two types. Of the total 195 rotational behavior patterns observed, only three wind patterns, performed as chaffing, led to the dislocation of a sharksucker, implying that the shark's primary intention may not be to shake off the teleost, but to initiate a position change to a less sensitive part of its body. Three sharks showed behavior patterns resembling typical agonistic display patterns, but they were induced by sharksuckers, not triggered by the presence of humans.

The subject of this investigation was spatial and spatio-temporal shark attack clusters occurring along California‘s coast between 1994 and 2010. Two hypotheses were postulated: (a) Shark attacks are proportionate to human beach activities. (b) No pronounced space-time relationship between human beach activity and shark attacks exists along this coast over time. The hypotheses were tested by using SaTScan TM version 9.1.1, a spatial scan statistic program. The results show that well-defined high- and low-risk areas have prevailed along the coast over the years. Because most attacks in California waters are attributed to white sharks, this animal was used as a model species to discuss the results.

Sharks possess a variety of pathogenic bacteria in their oral cavity that may potentially be transferred into humans during a bite. The aim of the presented study focused on the identification of the bacteria present in the mouths of live blacktip sharks, Carcharhinus limbatus, and the extent that these bacteria possess multi-drug resistance. Swabs were taken from the oral cavity of nineteen live blacktip sharks, which were subsequently released. The average fork length was 146 cm (±11), suggesting the blacktip sharks were mature adults at least 8 years old. All swabs underwent standard microbiological work-up with identification of organisms and reporting of antibiotic susceptibilities using an automated microbiology system. The oral samples revealed an average of 2.72 (±1.4) bacterial isolates per shark. Gram-negative bacteria, making up 61% of all bacterial isolates, were significantly (p