The phrase "short tail" refers to a situation where there are only a few options or possibilities available. It means there are limited choices or outcomes for a particular situation. Full definition
They are born with short tails which never need to be cropped. (bulldogmixes.com)
They have long, silky coats that protect from the cold climate and a very short tail. (animalbehaviorcollege.com)
A small mouse and a dwarf hamster can be about the same size, 2 inches, but the hamster's much shorter tail means he has a larger body than the smaller mouse. (animals.mom.me)