Tigers and bears don't seem to have any emotional strife about their position in the food chain. Don't think we should feel too bad about it either. There are real concerns to address about sustainability though.
To be clear, holding tigers and bears to a different moral standard is human exceptionalism. I’m fine with that, but many people seem to feel we should treat animals humanely because they’re the same as us.
If they are, we owe them moral treatment, but then they are subject to being held accountable for their own moral failings.
If they're not, then they can't be said to accrue any moral failings, and we don't owe them moral treatment.
Also, just because we don't "owe" it to them doesn't mean we shouldn't. Being nice or doing good in the world isn't something that should be earned by the recipients, it should be the default for how we treat each other if we're REALLY trying to progress and move forward as sentient beings.
What should be included in the set of "each other"? You're suggesting we include entities that are totally amoral, who happily destroy other sentient beings in the most painful ways, and who are incapable of reform. There is no imaginable social contract that could possibly include such monsters.
Surely there must be some element of symmetry as a condition of such a set membership. It's implied by the very phrase "each other".
IMO, the correct 'null hypothesis' wrt mammals is that they think and feel like humans do, except where we've managed to prove otherwise.
If you are going to survive, you have to kill every day, be it plant or animal; it's just the way it is. You can say that plants matter less than animals, and make up some justification about consciousness and suffering, but that is simply our own personal bias. There is no way to know if the universe cares more about thinking or non-thinking things, or if they share the exact same intrinsic value. All such moralizing is on very shaky ground and comes down to human bias and not much else.