I can't find a reference for polar bears, but it's probably the same as for grizzly bears where they use a mixture of Xylazine (https://en.wikipedia.org/wiki/Xy

I can't find a reference for polar bears, but it's probably the same as for grizzly bears where they use a mixture of Xylazine (https://en.wikipedia.org/wiki/Xylazine https://en.wikipedia.org/wiki/Xylazine) and Telazol (https://en.wikipedia.org/wiki/Tiletamine https://en.wikipedia.org/wiki/Tiletamine), a dissociative in the same family as Ketamine. So not a paralytic, but the animal retains memory of the experience. http://www.mammalogy.org/uploads/Cattet%20et%20al%202008.pdf http://www.mammalogy.org/uploads/Cattet%20et%20al%202008.pdf documents the process of helicopter darting and reports substantial health and behavioral changes for weeks after capture.