I think you must mean the boreal coniferous forests, which occur between the temperate forests and the north pole. The boreal coniferous forest was once home to the Pleistocene megafauna, a group of animals that were particularly well adapted to the glacier era, and most of which are now extinct.
The Pleistocene megafauna included woolly mammoths, mastodons, giant cave bears, saber toothed cats, dire wolves, giant beavers, and several species of elk. All of these animals were massive, and carried heavy pelts; both are adaptations to conserve body heat. Only a couple of representatives of the megafauna are still around, bison, musk-ox, and moose being among them.
The major driving force behind the extinction of these animals was probably climate change when the glaciers receded and the weather became warmer in the boreal regions. However, some researchers believe that human hunters were also a factor in these extinctions.