The Marsh Pride's story deepens through voices of those who film, protect, and oppose them - revealing a fragile future as human expansion drives lions toward decline.

Hurricane Harvey rips a coastal town apart and dumps a once-in-a-thousand-years rainfall that drowns Houston.

America's mighty Mississippi is under threat from alien invaders, toxic run-off, and massive man-made disruptions. Jeremy meets spirited Americans who want to fix the river's problems.

Gary, Arlie and Damon rescue two gators - one near a restaurant and the other at an industrial equipment supplier - while the team gets Gator Country ready for the busiest day of the year.

An old leopard queen is dead; when Thandi, the new queen, discovers the young cubs left behind, the fight for survival and for the crown of Djuma is on.

The duke is desperately ill, and a new male wants to claim his territory while trying to kill young Hosana and baby Tlalamba in the process.

Thanks to Hosana's exceptional hunting skills, Tingana rebuilds his strength, finally challenges Hukumuri for the dukedom, defeats him and keeps his cubs safe.

Meet Kenya's Marsh Pride in the Maasai Mara. As power shifts within the lions, rising human conflict and habitat loss threaten their fight to survive.

The Marsh Pride's story deepens through voices of those who film, protect, and oppose them - revealing a fragile future as human expansion drives lions toward decline.

The Alaskans must use the brief hours of daylight to build vital tools, maintain their land, hunt for needed food, and sharpen their survival skills.

In the Arctic, the search for water, firewood, and other vital resources is a never-ending quest. It requires Alaskans to explore remote locations unfit for normal human existence.

An unusually low snowfall and a late freeze-up in the Arctic presents new challenges to the Alaskans. Travel on the treacherous trails through the wilderness becomes more of a risk.

As winter approaches, the Hailstone family receive news of some land they have inherited. Meanwhile, after being stranded for days, Glenn attempts to return to his remote cabin.

A power outage in Kavik leaves Sue Aikens scrambling to restore her communications, while Glenn Villeneuve sets out on his most crucial hunt of the year.

Vet Shondie fights to save Tamascan puppy Leyla, Guy has a caesarean birth at a remote farm, David deals with elderly donkey Lerah, and Rebecca attempts to clip Squeaky the parrot's claws.

Vet Shondie needs to help two rescued grey seal pups, Guy operates on Bonzo the cat's hip, Tom completes dental work on mare Hallie, and chihuahua Zac needs an operation to sort a bladder problem.

For some animals, sound is key to survival. They use sound to hunt, defend, and escape. Great gray owls can detect voles beneath a foot of snow, kangaroo rats hear rattle snakes in the dark.

For some animals, sound is the key to finding a mate and to warn off the competition. Some sing the most melodious songs in nature to impress females. Some deep sea fish hum and bark their intentions.

This episode highlights the Belitsa Bear Reserve, the legends of the Rila Lakes and the ruins of an abandoned village on the Turkish-Bulgarian border where nature has been able to reclaim.

Migratory birds begin their annual journey south and like to stop off in the Belgium countryside; the gathering of cranes and their spectacular departure is a breathtaking spectacle.

Slovenia boasts a stunning variety of natural monuments, scenic landscapes and wildlife; the country has also been given top spot in a United Nations list of the most sustainable national lifestyles.

An old leopard queen is dead; when Thandi, the new queen, discovers the young cubs left behind, the fight for survival and for the crown of Djuma is on.

Dan O'Neill is on a mission to save the snow leopard. In Kyrgyzstan, there's a snow leopard that has never encountered humans. And in Mongolia, he tracks down the largest snow leopard ever recorded.