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Defense In The Sea | JONATHAN BIRD’S BLUE WORLD


Next on Jonathan Bird’s Blue World, a look at the amazing ways animals in the ocean cleverly defend themselves against predators! Hi, I’m Jonathan Bird and
welcome to my world! ( ♪ music ) The ocean is a tough environment to live. To
survive, every animal must eat, and that means that other
animals get eaten. And nobody wants to get eaten!
So… Animals in the ocean have come
up with a lot of ways to defend
themselves. They have spines,
venom, speed, maneuverability and even a
smoke screen. Come check out this fish! The lionfish has pretty obvious defenses—dozens of spines
sticking out in all directions. They’re not only sharp, but
venomous. Very few animals can eat a lionfish, especially when
it’s fully grown. A sting from one of these
spines is extremely painful. The stonefish has much less
obvious spines, but they are
considerably more venomous. A sting from one
of these spines will send a diver to the
hospital. Fortunately, these well-camouflaged fish pose no
threat to divers if we don’t
touch them. Stingrays only have a single
spine. It’s located at the base of the
tail, and can be pointed and
jabbed at a threat from above. Since
sharks love to eat stingrays, the venomous spine is used to
jab sharks that come too close. Every once in a while an
unfortunate swimmer steps on a
stingray and gets stung, but for the
most part, stingrays are not at
all aggressive towards people. In
the Cayman Islands, they are downright friendly! Fish aren’t the only animals in
the ocean with spines. Sea urchins have many sharp
spines with brittle tips. If an animal
gets skewered by one of these
spines, the end breaks off below the
skin and causes pain for months. Long-spined urchins are so well
protected that sometimes small
fish even use them for safety, hiding
between the spines where no
predator would dare trying to get them! Spines work so well for urchins
that some of their close relatives
the sea stars have spines too. The spines on the
crown-of-thorns sea star are every bit as sharp and painful
as those on an urchin. Believe me, I learned that the
hard way! Sea Cucumbers are closely
related to sea urchins and sea
stars. But most sea cucumbers have no
spines at all for defense. The sea cucumber has an even
more amazing–and
disgusting–way of getting rid of predators!
When attacked, many species of sea cucumbers
eviscerate from their mouth a
gooey mess called cuvierian tubules. These
sticky, stringy organs presumably give a predator
something unappealing to eat, and they are often accompanied
by the secretion of a poison. This combination prevents sea
cucumbers from being a popular
food item in the ocean! The sea cucumber can retract
the tubules, and replace the lost ones in a few weeks
and be ready to eviscerate
again! Some forms of defense are just
simple common sense. These fish are
staying within the protection
of a branching coral. They feed on
plankton that the current
brings by, but they don’t venture far from
the safety of the coral. Other fish are too big to feed
on plankton and must go out of the
protection of the reef if they
want to find food. Their defense is to keep an eye
peeled and be ready to zoom into the reef if a
threat comes along. Being alert is a key defense
mechanism. When it comes to a good
defense, nothing beats being
really fast. These sailfish can swim 60 miles per hour. They are top
predators in the open ocean, and even though sharks could
theoretically eat them, sharks can’t catch them! The
sailfish are attacking a small school of sardines. Schooling
is a defensive move used by fish in open water,
where there is no place to hide. This school of jacks stays together in a large
group, which helps protect the
fish because it makes it harder for a
predator to focus on a single
fish. It’s sort of a
safety-in-numbers strategy. But what happens at night? Many fish sleep safely at night
by hiding in holes in the reef. For the most part
they are safe. The parrotfish creates a mucus
cocoon around itself every night. This bubble
protects the fish from annoying parasitic isopods—the
equivalent of an underwater
mosquito. This sleeping parrotfish has a
nice bubble that is doing its
job. Look closely and you can see
the isopod on the bubble, like a fly on a screen door! Nearby on the nighttime reef, an octopus is out on the prowl,
hunting for sleeping fish. It sticks its tentacles into
the reef to startle a sleeping fish, and hopes that
the fish will come out into its
web of arms it has wrapped around the
coral head. But how does the
octopus defend itself against bigger
fish and fearsome underwater photographers with bright video
lights? It squirts an ink cloud. The
ink cloud is a distraction to focus the predator’s
attention while the octopus
makes a quick getaway! On a reef in the Philippines, a
tiny octopus, barely larger than a bottle
cap, is hunting for a meal. It’s a Blue-ringed octopus, one
of the most dangerous animals in the world,
packing a venom 10,000 times more deadly than
cyanide. One bite from the Blue-ringed
octopus will kill a human in only minutes. Reaching into cracks and holes, the octopus hunts for shrimp or
small fish to eat. A goby boldly protects its
burrow. To a nearby scorpionfish, the octopus looks like a
bite-sized snack. The octopus doesn’t see the
well-camouflaged scorpionfish–watching and
waiting to make its move. The scorpionfish strikes… and gets more than he bargained
for. Within only a fraction of a
second, the octopus bites back, and the
scorpionfish spits it out. he scorpionfish will have a
sore mouth for days, if it even
survives. It turns out that the blue
ringed octopus does not make a very
good snack after all. Some animals are not blessed with spines, venom or even the
ability to move quickly. Crabs and lobsters have a tough
exoskeleton that makes them very hard to eat. As well, they
have powerful claws that can pinch and crush.
When a threat comes near, a lobster doesn’t hesitate to
put up those claws and use them! A hermit crab ups the defense
by using a snail shell as a
portable house, to provide an extra
layer of protection. Some hermit crabs take it even
another step further, placing venomous stinging
anemones on their shell to
further increase their defensive
positions. This crab might be
slow, but she is very hard to eat! Even a lowly scallop has a
defense. It has no legs for walking, or
fins for swimming. But when its arch enemy the sea star
approaches and makes a move,
the scallop opens its shells wide and claps
them together, squirting a jet of water out of
its mantle. Whelks are another predator
that try to take advantage of the scallop, but they are
given the squirt treatment too! Take that, whelks! No matter how vulnerable an
animal in the ocean might look, you can bet that it has a
strategy to survive. Spines, venom, speed, a smoke screen or even a squirt
gun. There are many ways animals
have learned to defend themselves in the blue
world. ( ♪ music )

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