Just-hatched goslings must leave their nest precariously perched on an aerie. Water and food are a mile away and winged predators circle. Too young to fly, the only option is to jump. A tiny ball of fuzz crashes into rocks on its 400-foot drop, and it’s gut wrenching to see. Three chicks make this miserable descent during a haunting eight-minute scene in Mountains, the opening installment of National Geographic’s docuseries Hostile Planet. Be warned: Two of the three hatchlings meet tragic ends, as do many animals in this six-part series premiering Monday, April 1.