Human souls are imagined by humans to give us comfort about the fact of death. Animal souls are imagined by humans for the same reason. As far as we know, animals do not practice religion, although it is possible some are capable of the abstract thought necessary to imagine an afterlife and wrestle with their own impending non-existence.
This is most likely not common, but there are some species that really do have incredible capacity for intelligence. Frankly, contemplating whether animals have souls seems a bit beside the point. The more relevant question is “How badly are we allowed to treat animals without guilt?”
Which is ultimately a personal decision based on the dictates of our own conscience. It is, however, a personal decision with global ramifications. Human economics is the single largest threat to natural resources. When beaver hides or elephant tusks or passenger pigeon meat becomes a commodity, those species are driven to or beyond the edge of extinction. When we stop appreciating a forest for what it is and instead see it as potential farmland, the habitat of thousands of species begins vanish overnight. Even with species we have bred to eat, when we stop seeing them as living beings and simply see them as little meat machines, we accept factory farm conditions that would have been unthinkable even to the livestock farmers of 200 years ago.
Even if we decide that individually animals have no rights and that a human should be allowed to treat an animal however they wish, when the aggregate effect of these choices made for economic reasons begins to threaten the very existence of a species, surely we must pause and weigh the cost. Do we want to live in a world with no lions or polar bears or eagles? Would it even be possible for to humans to survive a world with no rain forests to keep the air fresh or ice caps to maintain sea level?
These are not hypothetical questions. These are very real conversations being had around the world right now. As living things, humans have a connection to all other living things. We may have reached the top of the food chain, but if the chain is broken, we too will perish.
As the earth’s most powerful species, we have a responsibility to be good stewards. This means there will always be a tug and pull between economic and environmental interests which will play out at all levels, from political to personal. A perfect example of this is whether or not one should eat meat. It takes thousands of calories of plant matter and gallons of water and tanks of gasoline to get a steak to your plate.
Every time you choose meat instead of vegetables, you are choosing to use exponentially more resources for the same number of calories. So again, whether or not there is a moral imperative to treat animals a certain way, we should be aware of the costs. We have become so separate from nature. It would not be a bad thing if, as a prerequisite to being allowed to eat meat, a person had to visit a slaughterhouse or butcher their own food at least once.