Polar bears have white fur. what selective pressure may have led to the evolution of this trait?

Answer 1

Two natural selective pressures come to mind, the one between environmental coloring and camouflage as advantageous for inconspicuous "hunting", and the second: the correlation between hair translucency and the "warmth of the body", being advantageous in a positive feedback of "thermal homeostasis".

Answer 2

The fur is not white; it is translucent. En masse, it appears white. There are two factors. One is that the translucent hairs transmit the solar energy to the black skin, where it can be absorbed as heat. The other is camouflage.

Answer 3

Camouflage against a snowy background. White bears survived by hunting successfully. . Dark bears died out.