As we have learned, food preparation on Yom Tov is permitted based on the passage in Sh’mot (12:16). Nevertheless, this permits only activities that are directly related to cooking and preparing the food. Capturing an animal, for example, is too far removed from the food preparation to be permitted on Yom Tov. The third perek of Massekhet Beitza, which began on the last daf (23b), focuses on the question of how we define tzayid – hunting. Specifically the Sages try to define under what circumstances an animal is considered to be in one’s possession to the extent that it is ready to be prepared for food.
Mishna: If traps for animals, birds and fish were set on the eve of a Festival, one may not take anything from them on the Festival, unless he knows that the animals found in the traps had already been caught on the eve of the Festival.
While our Gemara bases its analysis of whether the animal was captured before or after the beginning of Yom Tov on the condition of the trap (i.e. when did the hunter discover that it had become misshapen by the animal trapped inside), the Talmud Yerushalmi distinguishes between places where there are many animals and places where there are relatively few.
In an area where there are many animals, the hunter can rely on the assumption that the animal became trapped in a relatively short time after the trap was put down.