Erich Ritter

Analysis of Sharksucker, Echeneis naucrates, Induced Behavior Patterns in the Blacktip Shark, Carcharhinus limbatus

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 sharks 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.

Do Sharksuckers, Echeneis Naucrates, Induce Jump Behaviour in Blacktip Sharks, Carcharhinus Limbatus?

Documentation of airborne sharks is scarce and much of it is anecdotal (Springer and Gold, 1989; Last and Stevens, 1994). With the exception of white sharks, Carcharodon carcharias (Anderson et al., 1996; Klimley et al., 1996), and some members of the family Carcharhinidae (Compagno et al., 1989; Castro, 1996), where pursuit of food is the likely cause of this type of behaviour, no other potential reason for sharks to jump has ever been described. During a study between April 2000 and November 2001 on the interaction between blacktip sharks, Carcharhinus limbatus, and sharksuckers, Echeneis naucrates (Brunnschweiler, 2002; Ritter, 2002), off Walker’s Cay, Bahamas, we noticed that irritation caused by sharksucker attachment on these sharks may be another likely reason to jump. Using SCUBA and digital cameras (Sony TRV 900 and Sony PC3, with Sealux housings), we randomly picked and videotaped blacktip sharks, independent of sharksucker attachment. Sharks without sharksucker attachment were used for comparison purposes. To avoid disturbing the sharks or triggering agonistic displays (Ritter and Godknecht, 2000), we stayed between 4 and 5m away from the animals, maintaining the same level and swim direction. We videotaped each shark for an initial 20 s. If during this time no behaviour occurred that was beyond a shark’s regular swim motion, the recording was stopped. If we observed an additional behaviour that was not swim related, further abbreviated as NSRB (Non Swim-Related Behaviour), the recording was continued for 20 s beyond the end of the last one of these behaviours. A NSRB was either a simple rotation along one of the shark’s body axes (roll, yaw, pitch) with a simultaneous bending of the front and tail area along the respective axis, a combination of these rotations, or any quick shaking of any fin (flicker), except the caudal fin (Ritter, 2002).

A geospatial analysis of shark attack rates for the east coast of Florida: 1994–2009

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 Floridas 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.

Are Caribbean reef sharks, Carcharhinus perezi, able to perceive human body orientation?

Abstract The present study examines the potential capability of Caribbean reef sharks to perceive human body orientation, as well as discussing the sharks’ swimming patterns in a person’s vicinity. A standardized video method was used to record the scenario of single SCUBA divers kneeling in the sand and the approach patterns of sharks, combined with a control group of two divers kneeling back-to-back. When approaching a single test-subject, significantly more sharks preferred to swim outside the person’s field of vision. The results suggest that these sharks are able to identify human body orientation, but the mechanisms used and factors affecting nearest distance of approach remain unclear.

An Estimation of Shark-Attack Risk for the North and South Carolina Coastline

ABSTRACT 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 Floridas coast, to quantify potential causes leading to elevated shark-attack rates, or the lack of them.

Do Lunar Cycles Influence Shark Attacks

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 peoples 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.

Mouth gaping behavior in Caribbean reef sharks, Carcharhinus perezi

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 gapes peak. Of all the possible functions discussed, a maintenance behavior to reposition the jaw elements after feeding fits all of the measured parameters.

Mating scars among sharks: evidence of coercive mating?

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.