Killing a bigger animal causes more bad karma than killing a smaller animal?
My knowledge in Buddhism is quite poor. IMO it is a greater sin to kill a larger animal than to kill a smaller animal but this cannot be the case always! Let me ask you a question. Which is easier, to kill an ant or to kill an elephant? Generally the effort and planning you have to go through to kill an elephant is much greater than to kill an ant. The greater the effort you are willing to put is because of the greater intensity of cruelness of your mind which makes it a greater sin. True physicality isn't what determines this. Hope this answers the question