Moray eels have been filmed purposely tangling
themselves up. Bizarrely, it may be a way to get food
If you’re struggling to find food, you might try looking in a
new place or perhaps setting a trap. You probably
wouldn’t tie your body into a knot.
But that’s what one species of moray eel has been filmed
Shanta Barley of the University of Western Australia in
Perth and her colleagues were studying moray eels on the
Scott Reefs off the north-west coast of Australia.
They lowered two video cameras on a metal frame into the
water. The frame also carried a plastic mesh bag
containing 1kg of pilchards, to lure meat-eating fish.
A fimbriated moray eel approached the bag and tried to eat
the pilchards. After struggling with it for a little while, it
grabbed the bag with its teeth and tied its “tail” region into
a loose knot.
Next the eel pushed the knot along its body so that it
struck the bait bag. It did this repeatedly.
Barley says it was probably trying to dislodge the
pilchards with the force of the impacts, and that tying its
body into a knot allowed it to concentrate all its force on
The findings have been published in the journal Marine
Several other species of moray eel have been observed to
tie themselves in knots, but for different reasons. In some
cases they may be trying to squash pieces of food that
would otherwise be too large to swallow.
Barley’s team also saw a second species, a honeycomb
moray eel , take an unusual approach to the bag of food.
The moray grabbed the bag with its mouth, then used its
tail as a paddle to push water towards the bag. This
seems to have provided it with extra leverage, twisting its
body hard enough to rip the bag open.
Barley says behaviours like these may be common in long
thin fish, such as eels and hagfish.
These fish are much more flexible than other species,
which makes it easier for them to perform contortions.
“Our observations suggest that having an eel-like body
shape opens the door to unusual and useful feeding
techniques unavailable to conventionally-shaped fish,”
These tricks may mean the morays can have a bigger
impact on their ecosystems than a predator of their size
would normally manage.
That’s because they can eat prey that are larger than their
mouths, which most fish can’t. In other species, “you can
largely predict the size of the prey based on the size of the
fish’s mouth,” says Barley. “Morays appear to have
cunningly circumvented this annoying biological rule of
Top predators like sharks have a powerful effect on the
ecosystems they live in. Often they allow a greater range
of species to flourish, by keeping the populations of
medium-sized species in check.
It could be that the morays are playing a similarly crucial
role. “If morays are using all of these fancy tricks to eat
lots of large prey, they could be having a really key impact
on coral reef food webs, and therefore ultimately the
health of the reef itself,” says Barley.