Evading Reef Predators When Chased
When a predator launches an attack, it is time for prey animals to get out of the way with all speed. Of course, anywhere will do to start off with, so long as it is away from danger. However, if the prey animal is cut off from safety, then its life really is in peril. For this reason, reef animals of all types seldom venture too far from their refuge in case they need to beat a hasty retreat.
How do mobile invertebrates escape when a predator approaches?
Invertebrates use a variety of tactics to accelerate out of harm's way. Many involve a form of jet propulsion, or incredibly fast muscular contractions, to power themselves beyond a predator's deadly intentions. These highspeed maneuvers not only serve to surprise a hunter; ideally, they should also take the prey animal out of sight and give it a chance to hide while the predator is still wondering what happened.
Clams use jet propulsion to shoot out of also use a kind of jet propulsion to escape trouble; many species also leave a decoy cloud of ink behind as they shoot off. Several of the prawns, too, can suddenly disappear from a predator's field of view with a sudden flick of their tail. When attacked by starfish, whelks turn into miniature bucking broncos - rocking furiously in an attempt to dislodge their assailant
What happens if a prey fish is caught in the open?
When this happens and the route to safety is cut off, the odds shift heavily in favor of the predator. But the game is not quite over yet; prey fish still have a few tricks up their sleeves! This is why most predators launch ambushes from hiding places or surprise their prey by attacking them from any blind spot, such as from below when they spot the silhouette of their quarry against the bright surface waters and sky.
Fish under attack often adopt a swimming behavior known as "skittering." This refers to the way they dart about rapidly, and apparently haphazardly, turning sharply in different directions. Skittering makes it hard for predators to predict their quarry's next move and ultimately to catch it. As predators are usually larger than their prey and therefore faster swimmers, it would make little sense for an escaping prey fish to dash in a straight line - the predator would simply overtake and capture it. But the size of the predator also makes it less maneuverable and the prey exploit this factor with their sharp twists and turns. However, fish can only play this game for so long — skittering quickly exhausts them — so for safety they must quickly find a hiding place. Sometimes skittering succeeds in shaking off a predator, but faced with a really persistent hunter, the prey fish may double back and fall in behind the predator, accepting this rather dubious and possibly short-lived haven.