The North American Pleistocene (2.6 million to 10,000 years ago) is characterized by periods of glaciation and interglaciation.These were periods of very rapid warming followed by very gradual cooling. This would have presented enormour environmental challenges for a predator and would have forced great adaptability in prey and habitat. Smilodon fatalis lived through these changing environemnts. Perhaps one of the biggest challenges Smilodon fatalis would have faced was that of climate change.
It is believed that Smilodon fatalis 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 fatalis because it would have allowed it to prey on animals from the transition between wooded and open habitats. They differ from one of the other large predators at the time, the dire wolf, which is believed to have crossed deep into the wooded and the open areas.