The North American Pleistocene inhabited by Smilodon fatalis was a tumultuous land of variability and change. Perhaps one of the biggest challenges Smilodon would have faced was that of climate change. Latest evidence indicates that the Pleistocene experienced great climatic fluctuation. This appears to have often manifested as periods of very rapid warming followed by very gradual cooling. This would have presented enormous environmental challenges for a predator and likely would have forced great adaptability in prey and habitat.
It is believed that Smilodon inhabited marginal and transitional areas between true woodland and true plains. This type of habitat is not preferred by any modern cats, but could have been ideal for Smilodon because it would have allowed it to prey on animals from the transition between wooded and open habitats. They differ from the other large predator at the time, the dire wolf, which is believed to have crossed deep into the wooded and the open areas.