The natural fur of the polarbear is highly UV activ, did you know that?
Just now, when UV activ materials get more popular year by year that's a nice fact to know and work with it on flies.
Sadly with some colors whyle dying, the effect is gone.
The fur is quite stiff and keep your flie in that shape you tied it. The fluffy underfur can be used as Dubbing or as a "bitepoint" behind the eyes and the long fibers can be used as shirmpantennas.
And there is quite a lot of legal polabear fur in the stores, specially in Denmark because Greenland is a part of it and there they still have to shoot them to protect themselvs.