There is no evidence that world climate change killed off any species ever. We do know that local change has killed off animals in a certain local but not world climate change. Even with local change they are not killed of world wide.
More likely they were hunted to extinction
The "climate issue" is only supplied assuming some sort of "canopy theory" of the pre-flood world, or something to that effect. It may or may not be accurate...I think the theory has legs. I agree that hunting had a major effect on them as well.