灰北极熊或北极灰熊是灰熊跟北极熊的杂交后代，这不多见的现象在野外或人为环境中均有出现，而且这类杂交种的后代均具备完整的生殖能力，显示北极熊与棕熊之间的生殖隔离并不完整，两者的关系比人类之前所认为的还要紧密，因此一些分类学家认为北极熊可以被视作棕熊的亚种。
2006年，一位猎人在加拿大的北极地区射杀了一只奇怪的熊，它的皮毛如同北极熊一般呈现出白色，但夹杂着褐色斑点，长爪子和弓起的背部又表现出灰熊的特征来。
In 2006, a hunter in the Canadian Arctic shot a bear that had white fur like a polar bear's but had brown patches, long claws and a hump like a grizzly bear's.
灰熊却能做到这一点，它们能够迅速击倒一头猎物，同时北极熊也能够闻到猎物的气味而随之分一杯羹。
Grizzliescan and do - but the catch is, as soon as a grizzly knocks one down, the polar bears will smell it.
灰熊进入北极熊的领地开辟了一个新的话题：在对北极熊过去的探索的中途，展望他们基因的未来。
The arrival of grizzlies into polar bear country opens up a fresh set of questions about the polar bear's genetic future in the midst of new discoveries about their past.
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