A pelagic and gregarious species (1), the cownose ray forms large schools which move gracefully through the water column propelled by undulations of the wing-like pectoral fins (4). Feeding takes place on the seabed, with the cownose ray detecting its prey by sensing movement as well as weak electric signals. In order to extract buried prey, the cownose ray sucks and vents water through the gills, thereby fluidising the surrounding sand, which is further cleared by stirring motions of the pectoral fins (2) (5). The food is then manoeuvred towards the mouth with the aid of the two lobes beneath the head, and sucked inside. Inside the mouth, it is crushed by the plate like-teeth and the edible parts separated from the indigestible parts, which are expelled through the mouth (5). Prey typically includes bottom-dwelling fish, crabs, lobsters and marine molluscs, such as bivalves (2). The large scale disturbance to the seabeds caused by the feeding behaviour of schools cownose ray have led to this species being implicated in extensive damage to seagrass beds and commercial shellfish beds (1). The cownose ray is preyed upon by a number of larger species such as cobia (Rachycentron canadum), sandbar sharks (Carcharhinus plumbeus) and bull sharks (Carcharhinus leucas) (2).
The cownose ray is believed to breed between June and October. Like many sharks and rays, the mode of reproduction is via ovovivipary, in which the females produce eggs, which after fertilisation hatch internally, so that the young are “born” live. While inside the uterus, the embryos are initially nourished by the egg yolk sac, but once hatched receive additional nourishment from a nutrient-rich fluid produced by the lining of the mother’s uterus. While one female was observed to carry six young to full term, in general the cownose ray produces only a single young, which is born measuring around 36 centimetres in body width (2).
The cownose ray makes long migrations in schools which can number thousands of individuals, moving northwards in late Spring and southwards in late Autumn (1) (2). Migration is believed to be initiated by the orientation of the sun and by water temperature (2)