"...Your animal nature is a fundamental form of identity on which the normativity, your moral identity, depends. It is not just as human but considered as sensible, considered as an animal, that you value yourself and are your own end.... If you don't value your animal nature, you can value nothing. So you must endorse its value. ....Christine Korsgaard, The Sources of Normativity, pp. 152-153
When you pity a suffering animal, it is because you are perceiving a reason. An animal's cries express pain, and they mean that there is a reason, a reason to change its condition. And you can no more hear the cries of an animal as mere noise than you can the words of a person. Another animal can obligate you in exactly the same way another person can. It is a way of being someone that you share. So of course we can have obligations to animals."
Many people don't see much use for philosophy. We know what's important, we do what we think is best, it's not hard to realize what the right thing to do is. Some people will even glibly say that they don't worry too much about morality, they just look out for themselves. But a lot of people do see reason to care about others. Thomas Nagel writes:
"There are so many people one can barely imagine it... what happens to them is enormously important, as important as what happens to you. ...what happens to anyone matters the same as if it happened to anyone else ... the elimination of the worst sufferings and deprivations matters most ... The alleviation of misery, ignorance, and powerlessness and the elevation of most of our fellow human beings to a minimally decent standard of existence, seem overwhelmingly important."Equality and Partiality pp. 11-13
This seems obviously true, and not requiring much argument. But it also seems to miss a lot. There are even more, many times more, individuals who are not humans, whose lives are very important as well. Some argue that their lives are less important; perhaps this is so, but their staggering outnumbering of humans seems to count in their favor.
What happens in the lives of animals, human and non-human, matters a great deal to them. There are many arguments (for example, Korsgaard's, summarized above) that it should matter to us. To some extent, we need no argument. We know that these things matter. But humans have also historically gotten morality very wrong, so it is imperative to be vigilant about these topics. Most people today still give far too little weight to the interests of non-humans, or particular groups of humans. And oftentimes, even when we acknowledge those whose interests matter, it's not clear what obligations follow. Discussion and analysis of the issues at hand can make it clearer who matters, and what we should do about it.