Sabre-tooth tigers, the common name for the smilodon, were a species of sabre-tooth cat that lived in the Pleistocene, or Ice Age, era. Although they are commonly called sabre-tooth tigers, they are not closely related to tigers, or any other modern cat.
On January 8, 19654 B.C., Marty McFly and Doc Brown are temporarily left stranded by Marcus Irving. They manage to barely escape sabre-tooth tigers, as Marty got scratched in the face. They rushed to a rock that Doc knew was still solid in 1986, and waited for Irving to return in his Yugo time machine. As Doc theorized, Irving was afraid of the butterfly effect their presence could cause that far in the past. He picked them up, had one of his androids treat Marty's wound, then brought them back with him to 1997.