As we travel south, so the sun’s influence grows stronger. And at 50 degrees of latitude, aradical transformation begins. Summers here are long enough for broadleaf trees to replace conifers. Broadleaves are easier to eat and digest, so now animals can collect their share of the energy that has come from the sun. It’s summer. And these forests are bustling with life.

But the good times will not last. Broad leaves must be shed in winter for their damage by frost. As they disappear, so the land becomes barren with little for animals to eat.

The inhabitants must migrate, hibernate or face months of near starvation.

The Amur leopard, the rarest cat in the world. Here, in the deciduous forests of eastern Russia, the winter makes hunting very difficult. Pray animals are scarce. And there’s noconcealing vegetation. The cub is a year old and still dependant on its mother.