S31.E10 ∙ The Mystery of Eels

Celebrates the remarkable comeback of one of the world's most iconic animals. Tiger populations have rebounded so successfully, many of the big cats are venturing from India's forest reserves into farms and villages.

Documentary follows trees that are transported, at great expense and inconvenience, from the coast of the Republic of Georgia to the private garden of that country's former prime minister.

When Peter Wohlleben published his book "The Hidden Life of Trees" in 2015, he quickly entered bestseller lists. The forester wrote vividly about his experience that trees are able to communicate with each other, a thesis explored here.

Follow a multi-generational orangutan family through their treetop triumphs and travails in this immersive documentary narrated by David Attenborough.

Fifty years ago there were close to half-a-million lions in Africa. Today there are around 20,000. To make matters worse, lions, unlike elephants, which are far more numerous, have virtually no protection under government mandate or through international accords. This is the jumping-off point for a disturbing, well-researched and beautifully made cri de coeur from husband and wife team Dereck and Beverly Joubert, award-winning filmmakers from Botswana who have been Explorers-in-Residence at National Geographic for more than four years. Pointing to poaching as a primary threat while noting the lion's pride of place on the list for eco-tourists-an industry that brings in 200 billion dollars per year worldwide-the Jouberts build a solid case for both the moral duty we have to protect lions (as well as other threatened "big cats," tigers among them) and the economic sense such protection would make. And when one takes into account the fact that big cats are at the very top of the food chain-and that their elimination would wreak havoc on all species below them, causing a complete ecosystem collapse-the need takes on a supreme urgency.