(Mishnah): We may not raise small animals (i.e. that do not work) in (settled parts of) Eretz Yisrael, but we may raise them in Surya or wildernesses of Eretz Yisrael.

We may not raise chickens in Yerushalayim due to [bringing Tum'ah to] Kodshim. Kohanim (who eat Terumah, may not raise them anywhere) in Eretz Yisrael, due to Taharos.

One may not raise pigs anywhere. One may raise a dog only if it is tied on a leash.

We may not set traps for doves, unless it is distanced 30 Ris (four Mil) from settled areas.

(Gemara - R. Ba): [One may raise small animals in a wilderness] such as Mahir, which is [a square] 16 Mil by 16 Mil.

Question: Even in Yerushalayim [we may not raise small animals]. Or, [it is permitted] like R. Yehoshua ben Levi taught "Yerushalayim ha'Benuyah [k'Ir she'Chubrah Lah Yachdav]'' - a city that unites Yisrael to each other (all are partners in it, so we do not decree lest one graze his animals in others' fields)?

Answer (Mishnah): We may not raise chickens in Yerushalayim due to Kodshim, and Kohanim may not [raise them] in Eretz Yisrael, due to Taharos. (When Yerushalayim is unlike Eretz Yisrael, the Tana explicitly teaches so. We explained this like HAGAHOS R. DINAR.)