Hashem has commanded us to rest on Shabbat. It is forbidden to perform any work on Shabbat, as the verse states, “The seventh day is Shabbat for Hashem, your G-d; you shall not perform any work.” One of the thirty-nine works forbidden on Shabbat is trapping.
There are kinds of animals which are usually trapped or caught, such as deer, wild geese, fish, and the like. There are other kinds of living creatures which are not usually trapped, such as, flies and mosquitos. It is a Torah prohibition to trap (on Shabbat) kinds of which are usually trapped. However, it is permissible according to Torah law to trap animals or insects which are not usually trapped.
Thus, if one traps a type of animal, bird, or fish which is usually trapped on Shabbat, one is liable for Shabbat desecration. Although it is permitted to trap animals or other creatures which are not usually trapped, our Sages forbade trapping any animal or creature on Shabbat. It is therefore forbidden by virtue of a rabbinic prohibition to trap flies and mosquitos Shabbat, for our Sages banned trapping any living creature on Shabbat. (Shulchan Aruch, Chapter 316)
There is no connection between the forbidden work of trapping and the forbidden work of killing on Shabbat. Thus, if one traps an animal on Shabbat and then kills it, one is liable for two forms of Shabbat desecration: The first is trapping and the second is killing.
Summary: It is a Torah prohibition to trap a type of animal which is usually trapped or caught on Shabbat. Regarding types of wildlife or creatures which are not usually trapped, it is permissible by Torah law to trap them on Shabbat but our Sages forbade this. It is therefore forbidden to trap any living creature on Shabbat. In the next Halacha, we shall, G-d-willing, discuss some more details regarding this law.
