Summer in Yellowstone and a visiting male otter woos a female on the lake’s shore. But she seems a little distracted. Her two pups are nearby. They’re about ten weeks old and the time is right to lead them from the holt. Males are not above stealing food from cubs, so she makes it very clear that he is not going to be joining the family on their trip. This female grew up on the lake, so she knows where to take the cubs for a very special occasion. Yellowstone cutthroat trout amass in the mouth of a stream that feeds the lake, as they prepare for their annual spawning. But the trout must wait, the stream is still running fast, and is too turbulent for them to lay their eggs. It’s a nervous time for them, and for good reason. An osprey swoops down and catches a fish. With a brood to feed, it will be back. The otters arrive and the mother chooses her moment to lead the pups upstream, then leaves them to watch and gives them a lesson in hunting. She makes a trophy catch of a large trout full of eggs. She chews its tail first to make sure the fish can’t get away. While the pups are still demanding milk, the mother otter often keeps the whole fish for herself. Her pups are happy enough with the caviar. As the flow becomes slow enough for the trout to lay eggs there is a brief window of opportunity to spawn before the river gets too shallow to swim upstream. The female trout digs a trough with sinuous flicks of her body and the attending male fertilises the eggs as they are laid. Millions of new lives.