Getting into the Brain of a Shark: Most likely scenario of Erik Norrie’s case... The shark applied at least 2 bites (visible by the two lower jaw imprints). Both bites were of superficial nature. Such was not an error from the shark’s point of view but intentional and a “conscious attempt” to trigger a reaction in Erik. Erik was carrying fish and the shark - most likely a 4-5 ft long Caribbean reef shark, Carcharhinus perezi - did not treat Erik as a unfamiliar object per se but as a competitor (= the object with the fish). This triggered a reaction called “kleptoparasitism” (= stealing the prey from someone else by harassing the initial owner of the prey). Whenever sharks do that to each other, they apply mostly multiple, quick bites (snaps) to the gill or snout areas (which is then unprotected since the targeted shark has the prey in his mouth). The effect is that the initial owner most often drops the prey, ready to be taken away by the competitor. Whenever sharks do this to each other, the intruder is the dominant one, hence the initial owner does not fight for the prey but let’s it go. The purpose of kleptoparasitism is not to hurt the initial owner but to “encourage” to drop the prey. That is the reason that the wounds on humans are most often of superficial nature (the shark applies as much pressure as it normally does but not accordingly to the soft tissue of humans since the animal is not familiar with the human texture. Since sharks do not know what humans are they do not aim for a certain body parts when into “clepto mode” (Ritter & Levine, 2004, 2005). Such is the reason why spearfishermen often have wounds on arms, legs or their backs. Although the reason is not known yet, sharks do understand the body orientation of humans (Ritter 2013; Ritter et al 2013, submitted), hence why spearfishermen, swimmer and others hardly ever see the shark approaching. Selected literature: Ritter, E. K. (2012). Shark-Human Interaction. Situations Findings Recommendations. SharkSchool Publishing. Ritter, E. K. & R. Amin (2013). Are Caribbean reef sharks, Carcharhinus perezi, able to perceive human body orientation? submitted. Ritter, E. K. & M. Levine (2005). Bite motivation of sharks reflected by the wound structure on humans. J For Med Pathol. 26 (2): 136-40. Ritter, E. K. & M. Levine (2004). Use of forensic analysis to better understand shark attack behaviour. J Foren Odon. 22 (2): 40-46 Amin, R., Ritter, E. & L. Cossette (2013). An investigation of shark density and attack rates in California. J. Env. Ecol., in press. Amin, R., Ritter, E. & P. Kennedy (2012). A geospatial analysis of shark attack rates for the east coast of Florida: 1994-2009. Mar. Fresh. Behav. Physiol. 45 (3): 185-198.
Posted on: Tue, 10 Sep 2013 15:46:55 +0000
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