We as a society apply moral treatment to animals based on cultural norms.
In other words, it doesn't make people think twice when you hear about snakes eating rats, but then when a snake eats a puppy it makes front page news.
I think its wrong to feed a puppy or a kitten to a snake more or less because to me, puppies and kittens are companion animals that relate to us more - so these animals basically get better moral treatment? There are some people out there that are die-hard rodent fans (obviously out of the mainstream) that would cringe at the fact that their beloved pets are fed off to snakes without a second thought.
The same goes with reptiles. If people neglect a group of dogs/cats, the humane society breaks the door down, rescues the animals, and prosecutes the owners. If a group of reptiles are neglected in the same way, they die slow deaths and the authorities rarely if ever get involved. I'm just illustrating the different levels of moral treatment that society applies to different groups of animals.
In Asian countries, they eat cats and dogs. They are thrown, alive, in containers of hot oil that melts their fur and outer layers of skin off (saves time in the manual skinning process) and are then hung to dry. Most if not all are still alive (barely) at this point and are hung to die a slow painful death.
On the other hand, we in the U.S. have chicken factories where chickens are hung from their feet, alive, and go down an overhead conveyor and eventually run into a circular saw that removes their head which then drops down into a bucket as the rest of it moves on for processing.
The predator-prey relationship is not a pretty thing. Lions eating a water buffalo alive is not a pretty thing. Humans throwing cats and dogs into hot oil is not a pretty thing. The difference is that humans are rational beings and have a choice about how we treat animals - with that gift, shouldn't we be doing better?