Sacrificing one for the other.

I was trying to think of an example to post, and was honestly having a very hard time. However, I did find one interesting observation. Where can we say the duty lies when we feed our pets (such as a snake) live animals? You may be able to argue feeding your pet snake keeps it alive which it turn makes you, the human, happy, thus reflects another indirect duty. However, does this not create some hierarchy among animals; giving your pet snake more value than the mouse you are feeding it? I think this then means that we show direct duty to the snake in which we recognize our duty to sacrifice the mouse for the snake, because the snake is inherently more intelligent or valuable. This could be a stretch to view this scenario as a direct duty towards animals, but regardless I still think the way humans place animals in hierarchies and our reasoning behind this is an interesting debate.