Whale watchers in Madeira captured the astonishing moment orcas took down a pygmy sperm whale. According to newly published research, they may have documented the first known instance of orcas hunting a marine mammal in Madeira, a Portuguese island territory. The remarkable sighting gives scientists a new example of orcas’ complex predator behavior and raises concerns that they might prey on some of the region’s endangered marine mammals. Learn more about what this discovery could mean for Madei

The OceanXplorer heads to the Azores, following the elusive sperm whale to its hunting grounds, a mile beneath the surface. Nat Geo Explorer Aldo Kane pilots the inflatable boat to tag a sperm whale with a state-of-the-art camera tag. This camera tag will go into the deep with the sperm whale, to reveal the secret lives of these deep-diving whales. Watch OceanXplorers tonight from 5.30pm on National Geographic UK. Narrated by James Cameron. | National Geographic UK