New evidence of grey reef sharks (Carcharhinus amblyrhynchos) displaying chafing behaviors on whale shark (Rhincodon typus) individuals in the Maldives

Maldives are recognized as one of the most attractive countries for scuba divers and shark enthusiasts thanks to the biodiverse coral reef systems and the great abundance of megafauna. Consequently, the development of shark-related and eco-tourism activities emerged as a valuable and effective alternative to the fishing industry, becoming an important socio-economic source of income, not only within Maldives but also in many other countries. This richness in diversity and abundance of sharks, make this region the ideal area for studying shark bahavior and interspecific relations among different species sharing the same habitat. Advances in underwater video technology and involvement of people in citizen science have expanded our ability to investigate several aspects of the mysterios shark ecology and biology. One of them is shark behavior, primarily due to the challenges associated with observing, studying, and comprehending it. Among various intriguing behaviours observed, the phenomenon of sharks rubbing against ocean floor or rocks is common, whereas instances of interspecific sharks chafing behavior are much less frequent. This behavior, where a smaller shark rubbing against a larger species, utilizing dermal denticles to rid itself of parasites or dead skin cells, has garnered scientific interest in recent years. However, the full implications of this behavior, including its costs and benefits, remain yet not fully understood. In this context, we present new evidences of grey reef sharks (Carcharhinus amblyrhynchos; Bleeker, 1856) engaging in chafing behavior against whale shark (Rhincodon typus, Smith 1828) in the Maldives. These observations suggest that grey reef sharks may engage in chasing and chafing behavior for cleaning purposes or take advantage of larger sharks as an anti-predation tactic. These findings contribute to shed light on previously unexplored aspects of interspecies interactions among elasmobranch and highlights the need for further research into this topic. The occurence of such behavior across different regions suggests its potential significance in the ecological dynamics of shark populations.