Many students of the Gemara have been perplexed by a mysterious creature called the bardelas, which appears in several places in Shas. People ask, is it a cheetah? A hyena? A polecat? (And, some people ask, what the heck is a polecat, anyway?) Even Tosafos admits to being perplexed.
The answer is that it depends on who's discussing it.
The first reference to the bardelas is in the Mishnah, discussing the laws regarding which animals are classified as dangerous, such that their owners have a higher degree of liability for damage that they cause:
"The wolf, the lion, the bear, the leopard, the bardelas and the snake are muadin (rated as expected to cause damage). (Mishnah, Bava Kama 1:4)
However, while the authors and audience of the Mishnah, living in the land of Israel, were familiar with such Greek terms, the same was not true of the sages in Babylon, who had far less exposure to Greek culture. The Babylonian Talmud therefore asks what type of animal the bardelas is, and concludes that it is the hyena:
"What is the bardelas? Rav Yehudah said: The nafraza. What is the nafraza? Rav Yosef said: the afeh. (Talmud, Bava Kama 16a)
(While the reference to the bardelas in the Talmud here refers to the hyena, it seems that other references to the bardelas in the Talmud do not refer to the hyena. Instead, they are apparently a corruption of the word mandris, which refers to the mongoose, polecat, or similar such creature.)
Because the Bavli identifies the bardelas as the tzavua, it then runs into a difficulty: that Rabbi Meir adds the tzavua to the Mishnah's list, as an additional animal. The Bavli is forced to answer that the bardelas and tzavua are both the hyena, but that one term refers to the male hyena, and one to the female hyena. While the Gemara attempts to explain why this is necessary, the answer is forced.
Of course, from the perspective of Rabbi Meir (who lived in Eretz Yisrael and understood bardelas to refer to a cheetah), he was not adding a different gender of an already-named animal; he was adding a different animal.
And if it's not bad enough that I have to point out that the Bavli did not understand the Mishnah's terms, the Bavli then goes and speaks about how hyenas transform into bats, and then into thorns, and then into demons.
Siz shver tzu zein ah ZooRabbi!
Fortunately, I'm able to finish the chapter with an inspirational concept, based on Perek Shirah, about how the hyena is an essential part of the circle of life. With thanks to Rav Moshe Shapiro, who told it to me a number of years ago.
(For the definitive study on this topic, see Avraham Ofir-Shemesh, “The Bardelas in Ancient Rabbinic Literature: A Test Case of Geographic Identification” (in Hebrew), Mo’ed 14 (5764) pp. 70-80.)