My old cat used to do that, til the day we put her down due to god knows what, eyes were different sizes, at 15 years old, and it only weighed liek a pound. The other cat doesnt, he takes them away, because its us against him-hes not supposed to get out. So he knows anything he does outside, we dont like. It worked, he still catches rodents, but doesnt bring them up. And hes quite gentlemanly, always leaves them in one piece, somewhere around the yard.