This is an unpopular opinion, and should be wielded very carefully, but I think something often lost in these conversations is that the existence of a human behavior in an animal is not sufficient evidence that it's backed by the full weight of the human-like mental states. It may well be, but additional evidence must be presented.

As humans, we're strongly prone to anthropomorphize–I'm capable of ascribing human feelings even to inanimate objects–and so are prone to doing the above without rigor.

An extreme example: if you drop acid into the water in which a paramecium lives, it will fire up its cilia and frantically try to retreat. It's a single cell, there is no suffering or mental states, but it sure looks like it.

An ant could have a sad looking death, but it surely cannot reach the depths of human sorrow, and the related suffering, that a similar event could elicit. It can't mourn the time it won't spend with its children, or the ways its life could have gone.

I'm not proposing that everything between us and the paramecium cannot suffer, but that arguments in these areas must go beyond X has behavior Y, so X must have full mental state associated with Y.