The questioner for
got the question wrong, so the response was wrong too.
The question isn't do animals feel pain, because the consensus among animal behavorists is that they certainly do experience pain sensations which are in almost every way akin to the pain which humans feel.
The correct question is whether animals can experience "suffering", and by extension, whether it is possible to "torture" an animal.
For example, if someone were to step on your toe accidentally, a human (or animal) would feel a sensation of pain. But the pain would be momentary, and you wouldn't "suffer" from it unless you thought they had done it on purpose or vindictively. For that matter, a human can be harmed or "suffer" from some real or imagined act done to them when there is no pain (or even when there is pleasure) associated with the event.
The argument being made by some researchers is that all animals (including apes, dolphins, etc.) except humans lack the mental sophistication to reflect upon the reasons for or context of the pains they experience, and hence are unable to feel suffering or be tortured.
Of course, there are other convincing grounds for not inflicting pain on any animal, and whether or not the animal itself can be tortured, it could be torture for any humans directly involved or even just aware of what is being done, and hence objectionable for those reasons alone.
For the record, I do not advocate mistreating animals. And yes, I do recognize the danger to animal rights (whatever they turn out to be) of even discussing the possibility that there are meaningful differences between animals (in the wild, in the zoo, in the lab, in the home, or whereever) and humans which have important moral or ethical implications.
I invite anyone who cares to explore either side of this argument further to do so here.