JOEL SARTORE, National Geographic Photographer: More than 80 million years ago, the islands of New Zealand had almost no mammalian land predators. No bear or deer or foxes. Nothing with four legs and warm blood was stirring, literally not even a mouse. But there were plenty of birds and their main predators were other birds. Flying ones. With few ground-dwelling predators and plenty of food, some birds lost their ability to fly altogether. Eighty million years of evolution created an ecosystem with thirty-two flightless bird species, more than any other place in the world. There were 10-foot tall birds called moas, the world's heaviest parrot, Takahe, Weka, millions of kiwi birds. Together, they owned the forest floor. Some of these bird species needed a source of protein to survive and they preyed on critters like bugs. Really big bugs.
JOEL: Yeah, I’m very excited about these wetas, I think they are awesome and very interesting.
You have to have something in an ecosystem that eats leaf litter and consumes plant material as it hits the forest floor.
Instead of mice, these guys are the ones that scavenge all the plant life off the forest floor.
So these wetas are the New Zealand version of mice. They’re really important.
JOEL: Okay, cue the weta. So, these are wetas, huh?
NEIL ANDERSON, Conservation Ranger, Zealandia: These are Cook Strait giant weta. We’ve got a male and a female.
JOEL: These are basically big, flightless grasshoppers, right? Look at how big. Wow. And they’re sweet? They don't bite?
NEIL: They don't bite. They are herbivores -
JOEL: And they took the place of mice.
NEIL: Yeah, essentially. Gentle creatures. What they have is, they have defense mechanism, they have these spikes on their legs.
JOEL: Now, these aren’t rare, are they?
NEIL: These are rare, yeah.
JOEL: Are they really?
NEIL: They are very rare, yeah. Predation by rats and mice,
JOEL: And they’ve lost their ability to fly, like a lot of birds here in New Zealand.
NEIL: Oh, yeah, yeah. They’re essentially large crickets. And they’re so large, in fact, we put transmitters on them when we first introduced them.
JOEL: So, we’re ready.
NEIL: Okay.
JOEL: Let’s try white first.
NEIL: On the white?
JOEL: Sure. Look at that, that’s perfect. You’ve styled wetas before, haven't you?
NEIL: Yeah.
JOEL: Can I move him a little?
NEIL: Yeah.
JOEL: They’re – they’re interesting looking. I am trying to--, oh, look at that.
NEIL: The defense mechanism.
JOEL: Oh, awesome. That’s interesting.
By putting his spikey back legs up, the weta appears much more threatening—and probably less tasty-looking—to potential predators.
JOEL: If they go on black, we will get them on black.
NEIL: Watch him, they can move reasonably quick when they get their mind to it. I’ll get him. You got him?
JOEL: Yeah, I got him. He’s hanging on my finger. Ouch, ouch, there you go.
NEIL: There you go.
JOEL: That is a cool behavior, isn’t it? She thinks I am going to eat her? She got you now, right?
NEIL: Hooks, yeah…
OFF-CAMERA: What’s that feel like?
NEIL: Oh, it just feels like -
JOEL: Thorns on a rosebush, basically.
NEIL: Yeah, no, not even that. Really, really quite delicate, so you have to be real careful with them. There you go.
JOEL: The weta's finely-honed defense mechanisms were no match for what was to come. About a thousand years ago, a predatory land mammal showed up, us. With humans came rats, weasels, cats, dogs, even the house mouse. Basically, a lot of invasive species with a taste not only for weta, but birds and their eggs. The forest floor was no longer safe and in no time at all, many bird species went extinct or close to it. Including the kakapo, the rarest flightless bird in the world. To me, its face looks more like a mammal than a bird and amazingly, it can live as long as we do. Up to 80 years. Weighing close to 10 pounds (4 kilograms), the world's heaviest parrot had to figure out a way to hide. As it stopped flying, it learned to freeze, put its camouflage feathers to work, and let its predators go hungry.