Predator avoidance by mesopredatory benthic sharks in response to potential predators in a natural environment

Abstract

Some benthic elasmobranch mesopredators utilise crypsis to avoid predation by higher trophic predators. While this ability has been documented in various elasmobranchs such as rays, cryptic behaviour has been scarcely documented in catsharks (family Scyliorhinidae). Freezing behaviour by leopard catsharks Poroderma pantherinum and shysharks Haploblepharus spp. in response to sightings of a smoothhound shark Mustelus mustelus and Cape fur seals Arctocephalus pusillus pusillus was recorded during four separate baited remote underwater video (BRUV) deployments near Gansbaai, South Africa. Catsharks were seen actively swimming (foraging) most of the time (97.72%), and occasionally resting on the bottom, showing active buccal pumping. In the presence of a potential predator, they rapidly ceased all movement, including decreased gill movement, and immediately sank to the bottom. This response was initiated only when the predator swam into visual range of the catshark, and thus the freezing behaviour seems to be induced by visual cues only. The freezing behaviour is suggested to complement the colour pattern of the species in camouflage. This finding of predator avoidance behaviour in catsharks may inspire future research on predator recognition and avoidance to gain further insight into sharks’ predator–prey behaviour.