BS"D
Shalom.
The snake is cursed 7 times more than the donkey, because the donkey was cursed 7 times more than the shortest chayah (cat-52 days).
Opinion #2 in daf 8b says the cat was chosen in order to maximize the ratio of 7, which is a punishment for the snake. If this is true, why Hash-m chose the cat (52 days)? He should have chosen an arnevet or a shafan or a mouse whose gestation (20-30 days) is certainly shorter than a cat's. Thus, the opinion #2 in Bechorot 8b which says that Hash-m intended to maximize its punishment seems not plausible. How can we explain it?
Yasher koach and Todah Rabbah!
Rephael Anzarouth
Dear Rephael:
The Gemara needs the shortest Chayah, not Behemah. It seems Arnevet and Shafan (and Gamal!) are in the Behemah category. See Kil'ayim 8:6 and in Tosfos Anshei Shem there concerning Chazir. A mouse is Achbar which is a third category called Sheretz and thus cannot be called a Chayah either.
All the best,
Reuven Weiner