NATURE - Season 42

♪ Look around ♪ ♪ Look around ♪ ♪ And drink it in ♪ (thunder crashing) ♪ Don't stop me now ♪ ♪ Don't stop me from singing ♪ - [Narrator] On an Australian island at the end of the world, one man gets a life-shattering diagnosis.

- [Pete] I didn't feel right.

I had a really strong headache for about a year.

A neurosurgeon noticed just a heap of lesions in my brain.

- [Narrator] A nature lover, Pete turns to the stream that runs through his home city for solace.

- [Pete] I think destiny probably drew me to the waterway.

- [Narrator] There, he meets a very special animal.

- I couldn't believe it the first time that this platypus just zoomed right up to me and put a bill out of the water and started wiggling it.

- [Narrator] It was the first of many encounters, so Pete named her Zoom.

- [Pete] It felt like a doorway had opened.

The magical portal into the world of the platypus.

- [Narrator] This egg-laying, duck-billed mammal is perhaps the most unusual creature in the animal kingdom.

- [Pete] But then one day, I came across Zoom, and everything changed.

I saw that there was a plastic ring around her bill.

(camera clicking) I felt helpless.

It was as if the natural world was trying to deliver a message: you have to do something to help the platypus.

♪ You can let in the light ♪ ♪ And let it show ♪ - [Narrator] If you come across a jam of cars in Wyoming's Grand Teton National Park, it's possible you're about to see a very famous wild animal.

- Grizzly Bear 399, she's known as the matriarch or the queen.

- [Narrator] At 27 years old, Bear 399 is believed to have 22 descendants and is thought to be the oldest known female with cubs.

- 399 is on the road to international fame.

- [Narrator] Her rockstar status led photographer Tom Mangelsen to chronicle her life.

- I've been documenting 399 for 15 years.

You think about what this bear has gone through in her 27 years of life, raised all those cubs, all the brutalness of winter, all the lack of food.

- [Narrator] Season after season, this mother and grandmother survives.

- [Tom] She's an extremely incredible bear.

None ever like her and none likely to ever come this way again.

(bright music continues) - [Narrator] Every year, shorebirds take to the sky for a marathon migration.

They follow eight major routes called flyaways.

Along the way, they must stop and refuel, but development and climate change are having an impact on their food source.

- [Speaker] When birds are on migration, little bits of habitat are disappearing, disappearing, disappearing.

(thunder crashing) - And also face hunger and starvation.

- We see a population that is declining because of all kind of problems.

Our studies on birds actually can contribute to making a better world.

We can learn from the birds as canaries in the coal mine, because they tell a global story that the world has troubles.

♪ Don't stop me now ♪ ♪ Don't stop me from sayin' it ♪ - [Narrator] In the African wilderness, there are three rivals whose worlds are about to collide: a lioness on the run with her cubs, a lone leopard possessive of her territory, and a pair of cheetah bachelor brothers looking for mates.

(lion roaring) But in a land where they keep bumping into each other, how will these big cats survive?

♪ You can let in the light ♪ ♪ And let it show ♪ - [Narrator] The world's oceans are still shrouded in mystery.

An alien world with wondrous animals (water sloshing) and strange gatherings.

To unlock these secrets of the deep, the "Spy in the Wild" series continues with perhaps their most ambitious mission yet: 30 new spy creatures will infiltrate almost every ocean on the planet.

Custom made to resemble the animals they're filming, these incognito cameras capture moments of extraordinary intelligence and emotions.

Perhaps, we have more in common with these sea creatures than we think.

(bright music continues) (lions roaring) ♪ See the world in a brand new way ♪