To Save an Endangered Fox, Humans Turned Its Home into a War Zone

[Christina] Just kinda hanging out, right?

[Narrator] A decade ago, this tiny fox

was on the brink of extinction.

We've got a mama here.

Can I see your teeth?

[Narrator] Now, the Island Fox is back,

and it's coming off the Endangered Species List.

Mama, do you wanna go?

Why don't you go find those pups, huh?

It's an exceptional success to be able

to take a species off the Endangered Species List.

Particularly, the fox, it's the fastest mammal

recovery in the history of the Endangered Species Act.

[Narrator] For years, scientists like Christina Boser

have been working to restore the ecological balance

to the foxes' home, Do you feel better now?

[Narrator] Santa Cruz and the other channel islands

off the coast of Southern California.

[Christina] Santa Cruz Island is a very special place.

It's the most bio-diverse island in the California islands.

It has a great history of human use,

as well as a number of really special species.

[Narrator] Humans have used the island for ranching,

military operations, and recreation,

bringing new species into a fragile ecosystem.

(materials pouring)

Scientists are now doing everything they can

to protect and restore the island's ecological balance,

by waging war against the invaders,

from destructive ants to feral pigs.

These are pigs that had been brought over

by ranchers around 1850 or so,

and they attracted Golden Eagles,

which were a non-native predator,

and this Golden Eagle population

grew to the point that it was taking not just pigs,

but also consuming baby foxes.

[Narrator] Unable to cope with the Golden Eagles,

the population crashed to fewer than 100 foxes.

It's pretty clear what we had to do

to try to save the Island Fox.

[Narrator] Get rid of the feral pigs, all of them.

That task fell on a New Zealand-based group of hunters,

which killed over 5,000 swine.

Conservationists captured the Golden Eagles

and sent them back to the mainland.

The remaining foxes went into a captive breeding program.

Amazingly, it worked!

The fox population soared.

A decade later, from that last Golden Eagle capture,

we're seeing over 2,000 foxes on Santa Cruz Island.

[Narrator] Now, scientist are trying

to restore ecological balance to other parts of the island,

taking on the invasive Argentine ant.

[Christina] Argentine ants remove pollen from flowers,

they also kill other native ants,

and generally can affect the ecology of a place,

from the bottom up.

[Narrator] So Boser concocted a way to control them,

from the top down.

This helicopter drops what Boser calls

sugar balls of death onto Argentine ant populations

across the island's rugged terrain.

[Christina] We wanted to do an eradication.

And that had never been done

on an area this size, or scale or scope.

[Narrator] Argentine ants will stop

feeding if they detect a toxin,

but because the balls contain so little poison,

the ants don't know what hit them.

We haven't been able to find

any Argentine ants in months,

and it's pretty exciting.

We're also starting to see native ants

return to these locations.

[Narrator] Pest controllers are now using

Boser's Argentine ant control method around the world.

Ants aren't maybe as cute as foxes,

but I think we can also contribute to conservation

by studying some of the maybe less charismatic animals,

like the ants.

[Narrator] And Boser says conservationists

can apply the lessons of the fox recovery

and ant eradication to other imperiled species.

So we as a society made a decision

to protect the Island Fox.

She's in very good condition.

And I think, in the future climate change

is going to threaten a few other species

that we care about.

[Narrator] That protection will require

constant vigilance, to safeguard the island

from invading species.

You're obligated to keep a pulse

on the population for at least five years

after the foxes are delisted.

This means that we'll continue

to figure out how many foxes are out in the wild.

We'll also keep track on their survival rate.

And we'll also make sure that we're

vaccinating these foxes, because currently

the biggest threat to this population

is introduced diseases from the mainland.

You no go? Yeah, do you wanna go on?

(upbeat music)