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 10 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 them. This female grew up on the lake,
so she knows where to take the cubs for a very special trip.
Yellowstone cutthroat trout amassing in the mouth of a stream that feeds the lake.
They are preparing for their annual spawning. But the trout must wait.
The stream is still running fast, too turbulent to lay their eggs.
It's a nervous time for them, and for good reason.
She chooses her moment to lead the pups upstream. Then leaves them to watch
and gives them a lesson in hunting. A large trout like this,
full of eggs, is a trophy catch. She chews its tail first
to make sure the fish can't get away.
While the pups are still demanding milk, the mother otter will often
keep the whole fish for herself. Her pups are happy enough with 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 digs a trough
with sinuous flicks of her body, and the attending male fertilises
the eggs as they are laid. Millions of new lives.