This TED Talk features marine biologist Mike Gill recorded live at TED Global 2017.

Who here is fascinated by life under the sea?

Fantastic. Now, what did we just do?

Let's dissect this for a second. The simple action of an individual raising a hand led many others to do the same.

Now, it's true that when individuals in a social network have common priorities, it's often

beneficial to copy one another.

Think back to grade school and dressing like the cool kids made you cool.

But copying behavior is also common in wild animals.

For example, some birds copy the alarm calls of other birds

to spread information about approaching predators.

But could copying behavior in wild animals

affect entire ecosystems that we humans depend on?

I was led to this question while studying coral reefs,

which support millions of people through fisheries and tourism,

here in Africa and around the world.

But coral reefs depend on fish that perform a critical job by eating algae.

Because if left unchecked, these algae can kill coral and take over entire coral reefs,

a costly change that is difficult or impossible to reverse.

So to understand how fish may prevent this, I spy on them,

while they're eating algae,

which can be difficult for them to do in open parts of the reef exposed to predators,

some of which, on a rare occasion, appear to realize I'm watching them.

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