While the Gemara uses the term tereifa to denote any animal with a terminal condition that cannot be slaughtered as kosher since it will die within a short amount of time, the single case of tereifa that is mentioned in the Torah is when an animal attacks another animal and kills it (see Shemot 22:30). This most basic case occurs when the predator locks its claws on the body of the animal that is being attacked, and the poison in its claws enters the animal, threatening its life, According to the continuation of the Gemara, this poison “burns” in the body of the animal, injuring and puncturing its internal organs, which renders it a tereifa.
The example of a tereifa that appears in the Mishna is a wolf, and Rav Yehuda quotes Rav as teaching that in the case of cattle it is “from the wolf and upwards,” i.e. either a wolf or animals larger than a wolf like a lion. Ultimately the Gemara suggests that this teaching comes to exclude the case of a cat that attacks in a predatory manner. While one might have thought that the Mishna simply mentions ordinary cases of attacking animals, but that smaller animals would be included as well, Rav Yehuda teaches that in the case of cattle an attack by a cat would not be considered significant to render the animal a tereifa.
A wolf, canis lupus, is a predatory animal, similar to a dog. It grows to a length of between 3 and 5 feet and an adult can weigh up to 130 pounds. Wolves live and hunt in packs, which allow them to hunt not only small animals, but larger animals, as well. An attack by a pack of wolves can cause serious damage to a herd of cattle.
A cat, felis, is a relatively small predator that weighs between 7 and 15 pounds. We are most familiar with the common house cat – F. silvestris catus – but there are numerous types of wild cats, as well. From the Talmud it appears that there were ferocious wild cats that lived in close proximity to human habitation during the time of the Sages. These cats attacked animals much larger than themselves, such as sheep and goats, and there is even reference to a case when a child’s hand was bitten off by such a creature.