 The porcupine ray can sometimes be observed lying still on the bottom in the open or inside caves . It is known to form groups at Ningaloo Reef . Its diet consists primarily of sipunculids , polychaete worms , crustaceans , and bony fishes . When feeding it plows deeply into the bottom , expelling excess sediment from its spiracles in a plume visible from a long distance away . Parasites documented from this ray include the tapeworm Rhinebothrium devaneyi , the nematode Echinocephalus overstreeti , and the capsalid monogeneans Dendromonocotyle urogymni and Neoentobdella baggioi . The porcupine ray is aplacental viviparous , with the developing embryos sustained to term by histotroph ( " uterine milk " ) secreted by the mother . Mangrove forests serve as important habitat for juvenile rays . Males and females mature sexually at about 90 and 100 cm ( 35 and 39 in ) across respectively . 
