The Great War started and ended on Saturday, October 23, 2077 (http://fallout.wikia.com/wiki/Great_War)
The grizzly bear appears on the Flag of California, though they are extinct in the state, the last one having been shot in 1922. (http://en.wikipedia.org/wiki/Grizzly_bear)
Your pic (http://upload.wikimedia.org/wikipedia/commons/0/0e/Ursus_arctos_horribilis_map.svg) states that "historically" Grizzly Bears lived in Nevada, but gives no time reference for what "historically" is. Even under the best case scenario, it was 155 years between the death of the last grizzly bear and the start of the great war.
I don't see why they would come back to a nuclear wasteland, when they haven't come back yet in "our world". There would be little wildlife to support them and no conservationists to protect them.
1st: You missed my point completely.
2nd: I know when the great war was and I know what the California flag looked like before the war (real life), I am not stupid. You don't need to give me a source about the most basic fallout facts.
My point was. At some point in HISTORY. Grizzly Bears lived in Nevada. They could be found as far south as Mexico. With no humans around due to the Great War, they could have come back to Nevada.
3rd: I am not complaining about there being no bears, I am just saying there COULD BE.
4th: It is possible that there was a Two-headed Bear somewhere back in California which was the reason NCR CHANGED the old pre-war flag!
5th: All I am asking for is one UNIQUE two-headed bear and I don't really care if we get it, I just think it would be cool.