Marine Biology

Nocturnal Predators of the Ocean



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When dusk falls over the face of the waters, darkness underneath the ocean becomes profound, inky black.  Some sea creatures withdraw to their hiding places for the evening, but some emerge to stalk their prey—whether ambushing, chasing, or flushing them out from their lairs and trapping them.  These nocturnal predators have unique adaptations because of these habits.  Their qualities have positioned them at the center of the human imagination not only as some of the most intriguing creatures in the ocean, but in the entire animal kingdom.  Among these animals are the Moray Eel, the octopus, and many species of sharks.

There are approximately 200 species of Moray Eel in the world, mostly living in reefs.  They span in size from the smallest at about five inches, to the largest at about thirteen feet in length!  Divers and oceanic hobbyists may know the Moray Eel for their serpent-like bodies and ghoulish faces that pop out like jack-in-the-boxes from their coral or stone hiding places.  Though there are reports of them attacking humans, this is usually in the context of the disruption of their burrows, or when divers choose to feed them.  Eels have poor eyesight, hence may unwittingly take fingers from a tourist or two.  Generally, the eels rely on their senses of smell, and have been known to hunt with a species of fish called Roving Coral Groupers.  They communicate by bobbing their heads, and cooperating to drive prey from their hiding places with their slender, scaleless bodies as their hunting partners wait to corral the doomed animals as they flee.  Moray eels feed mainly on small fish, mollusks, crustaceans, and cephalopods.

The octopus is considered the most intelligent invertebrate, with myriad methods of hunting prey and escaping from –literally—tight spots.  Octopi are soft-bodied cephalopods, their only hard part a centralized beak that they use to rip the flesh of their prey.  Their skin is full of pigmentation cells that allow the octopus to camouflage itself when predators like Moray eels or sharks are nearby, and also allow it to camouflage itself as it waits to ambush its prey.  Octopi have the ability to regenerate arms that may be damaged or torn off through a process called autotomy.  During their captivity in places such as the Oregon Coast Aquarium, octopi have been known to break out of even the most secure tanks in the middle of the night to attack fish in other tanks, demonstrating their superior problem solving skills.  Only one type of octopus, the Blue-Ringed Octopus of Australia, has a poisonous skin lethal to humans; however some octopi have been known to attack humans when they feel threatened, by wrapping themselves around an appendage and shredding them with their beaks.  Most just stick to their diet of crabs, mollusks, and the occasional shark.

Sharks have the most insidious reputation of all ocean predators.  They are some of earth’s oldest creatures, and with over 400 species, they come in many different shapes, sizes and adaptations to their environments.  Most of them are nocturnal predators, though when they do sleep, they must remain swimming so that water passes over their gills, supplying them with oxygen.  Great White Sharks, of Jaws fame, are the most-maligned because they have a history of attacking humans—though only at a rate of about four humans per year according to the International Shark Attack File (ISAF).  Primarily, sharks that top the food chain (called apex predators), such as the great white, tiger, mako, blue shark, and hammerhead, feed on large and small fish, cephalopods, pinnipeds, and even other sharks.  Some, like the hammerhead, hunt in packs, gravitating toward large schools of fish for their prey.  Others, like the great white, prefer to live and hunt alone.

Eels, octopi, and sharks all have a particular allure to human beings, due to their hunting prowess and the fact that the night is their domain.  They’re also intriguing due to their other-worldly slickness, the eel with its mucus covering, the octopus with its eight flexible appendages, and the shark with its lithe, cartilaginous body.  Unfortunately, their legendary status sometimes makes these animals an unabashed target for human persecution, especially in the case of sharks.  Hopefully, though, further education will help humans not only to keep themselves safe, but preserve these species to live to hunt another night.

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More about this author: Emily Einolander

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ARTICLE SOURCES AND CITATIONS
  • InfoBoxCallToAction ActionArrowhttp://www.mysterra.org/webmag/moray-eels.html
  • InfoBoxCallToAction ActionArrowhttp://animals.nationalgeographic.com/animals/invertebrates/common-octopus/
  • InfoBoxCallToAction ActionArrowhttp://www.britannica.com/EBchecked/topic/45179/autotomy
  • InfoBoxCallToAction ActionArrowhttp://aquarium.org/
  • InfoBoxCallToAction ActionArrowhttp://www.imdb.com/title/tt0073195/
  • InfoBoxCallToAction ActionArrowhttp://www.flmnh.ufl.edu/fish/sharks/isaf/isafabout.htm
  • InfoBoxCallToAction ActionArrowhttp://www.sharkwater.com/