I’m not buying it. The yew tree is a poisonous plant – true. In fact the whole plant contains toxine alkaloid, ephedrine, a cyanogenic glycoside (taxiphyllin) and volatile oils except for the fleshy red part of the berry – that you can eat. But bears know better than to eat toxic plants. Otherwise, there would be dead bears lying all over the place. Plus – the seeds are only toxic if you masticate (chew them up). If they aren’t chewed up, they pass harmlessly through the gut into the stool. Plus a 300 pound bear would need to eat a massive amount of the plant and berries in order to suffer the cardiac effects that characterize taxus spp. poisoning. So what killed this family of bears? Heck if I know, but I think it is a long shot to say it was over consumption of yew twigs and berries.