This episode was brought to you by Skillshare.
Inés: Hey everyone!
Today I am joined by Virginia Schutte whom you may remember from a past video that we
recorded together on animal navigation through the open ocean – and we had such a lovely
time doing that the last time, that, we thought it was time to do it again with a new video!
Virginia: There is a simple reason that Shark Week is so popular and Planet Earth sometimes
feels like a list of predatory encounters: animals eating other animals is fascinating.
Every time a carnivore eats, it's a full story with characters, a conflict, and a resolution.
And as such, we are giving you today our top 5 most inventive ways that animals hunt together
in the ocean.
[Intro by Caro Waro & Cristina de Manuel]
Inés: Animals will only hunt if they gain more than they lose when capturing, killing
and eating their prey.
The details of the hunt become important in determining which way the scale tips: is it
going to be a long chase, or a short one?
Is it possible that the hunter could get injured during the hunt?
The expected costs must be less than the expected benefits for a hunting animal to choose to
go after a particular piece of prey.
Virginia: These hunt details are where there's room for cooperative hunting to emerge as
a good strategy.
Sometimes, everybody gets more food by working together.
The equation stays the same: is the gain for an individual worth the cost of hunting with
other individuals?
And things get really interesting when you add in cheaters and scavengers, who will sometimes
or even always let others do the work and then try to take some of the kill anyway.
Inés: Cooperative hunting is not rare in the ocean and this is because the ocean is
a big place and cooperation offers predators a chance to concentrate prey in denser patches
or otherwise reach prey that they wouldn’t be able to without working together.
Hunting in groups also confuses prey.
For example, sailfish either swipe left or right with their heads to snap up prey fish.
An individual sailfish always either swipes left or right, but hunting sailfish form groups
with almost exactly the same number of left- and right-swiping predators, so this means
that the prey never actually knows where the next attack might come from.
Virginia: Everything from squid to whales work together to corral, trap, or otherwise
corner their prey so they can eat.
We’re going to focus here on some of the more unique examples of cooperative hunting
in the ocean.
So, let’s start off with the orcas!
Orcas “wave-wash” seals off of small icebergs in Antarctica.
The whales line up, side by side, with their backs just under the surface of the water.
Then they swim together towards the iceberg, diving down right before they ram into the
ice.
The wave created by their swimming continues onto the iceberg, slamming into the seal and
sometimes knocking it into the ocean and if wave-washing doesn’t work, the orcas work
together to tip the iceberg over and they dump the seal into the ocean anyway.
Inés: Next up we’ve got the dolphins.
The classic examples of dolphins hunting together is that one dolphin drives fish towards a
dolphin barrier, causing the fish to leap into the air to escape, only to be eaten by
the dolphins at the water's surface.
But dolphins are very social and extremely intelligent, so they also have more specialised
hunting techniques.
Dolphins on the southeastern coast of the US spread out to corral fish towards a beach.
Using sound cues underwater, they signal one another and then all rush the fish at the
same time, crashing ashore in a heap.
The fish flop ashore ahead of them and then literally jump into the dolphins’ waiting
jaws.
Virginia: We’re still not done with dolphins yet though!
Other dolphins in Florida hunt in shallow, muddy waters.
They swim along the bottom, kicking up mud clouds with their tails as they go, muddying
the water in a large circle.
Then they spiral inwards slowly to tighten the circle until their prey fish are bunched
in the middle of their mud net.
Then they literally lie back on the water’s surface and wait for the fish into their mouths.
Humpback whales also make their own nets, but in their case the nets are made of bubbles
and the whales are chasing very small critters, like krill and plankton, which they engulf
with their huge mouth once these critters are concentrated inside the bubble net.
Inés: However, hunting parties aren’t always made of the same species.
Large fish on coral reefs are speedy eating machines in open water, but have trouble flushing
smaller fish out of hiding places in the reef.
So, in the Red Sea, these fish do the fish equivalent of a human pointing: a headstand,
paired with a head shake, lets eels or octopus know that there’s hidden prey right where
they’re pointing.
The flexible eels and octopus can either scare the smaller fish out for the larger fish to
eat or they might snag it for themselves and similar associations occur in the opposite
direction between predator fish that scare prey fish into the nooks and crannies of the
reef, where they’re eaten by slowpoke sea snakes that can wriggle into the hiding spot.
Virginia: And last, but definitely not least are some examples that involve humans!
There are 2 examples of wild, untrained marine animals voluntarily cooperating with humans
to hunt.
The first is a variation of the beaching strategy that dolphins use and we talked about earlier.
In Brazil, dolphins drive fish toward fishermen wading in the water, who then cast their nets
into the ball of fish.
The dolphins presumably benefit from the chaos, snapping up fish that scatter once the net
is thrown.
The second example involving humans was with orcas.
In the 1860s in Australia, a pod of orcas would drive larger whales into a bay and trap
them there.
Then the pod leader would swim up to a whaling station and slap his tail on the surface of
the water to signal that there were whales in the bay.
After capturing and killing the whales, the whalers would hang the carcasses in the water
so that the orcas could eat the tasty bits of the whales’ heads, leaving the valuable
parts, which the whalers would then harvest later.
Once the pod leader died the cooperative orca pod completely disappeared.
Inés: And these were our top 5 most unique examples of cooperative hunting in the ocean,
proof that corporate team-building exercises could be a whole lot more interesting.
Speaking of which, if you would like to learn cooperatively - perhaps not hunting in the
ocean but other productive skills such as video production, animation, programming and
more, then why not sign up for SkillShare?
I’ve been using them for over a year to learn and develop my own skills, and they
are currently offering 2 free months to any curious subscriber who would like to try them
out at over at skl.sh/drawcuriosity2
We really hope you enjoyed today’s episode, we had a lot of fun making it – thank you
so much to Virginia for coming up with such an original idea!
And as always you can find out more about her work over on her website at Real Life
Science – and as always, thank you for watching us, and I’ll see you in the next one!
Byeee!
[Music by: Thastor & CryoSleepKitten] [Scripting: Virginia Schutte]
[Hosting: Virginia Schutte & Inés Dawson] [Editing & Animation: Inés Dawson]
[Translated by {your name} into {language}]