The word “lovebirds” might apply to species you wouldn’t typically think of. Although it’s nearly impossible to know if animals feel love like humans do. Prairie voles, for example, couple up for life. (Todd Ahern/Emory University/AP)

Even some of the least sappy humans get a little mushy about love around Valentine’s Day. Do other animals love their mates — or family, or friends — in the same way we love one another?

You might think you know what your pets are thinking, but it’s incredibly difficult, if not impossible, for us to understand how nonhumans experience the world.

Let’s use dogs as an example: On the one hand, studies show that when pups make eye contact with humans, both species get a boost of oxytocin (OCK-see-TOE-sin). That’s a chemical scientists don’t totally understand, but they know that our bodies make more of it when we’re forming social bonds and that it often makes us feel good. In humans, at least, it’s an important ingredient for making a love connection.

But even when there are signs that animals have humanlike feelings, it’s tough to know whether we’re just projecting our own experiences.

Some studies suggest the guilty look your dog makes after destroying something isn’t a sign they feel bad about it. It might be just a face they make when they can tell you’re unhappy, which isn’t quite the same as feeling shame.

All of this is to say that we can observe how animals behave — and even take a close look at how their brains and bodies act in response to certain situations — but we can’t know how they feel. No one can tell you that you’re happy or sad or hurt; if you think you feel a certain way, then you do. Because we can’t ask a dog or a cat or a bird whether it feels pain, anger or love, we can only guess whether it does based on its similarities to humans.

Bald eagles usually keep the same mates season to season. (David Joles/AP)

A chimp has a brain and body relatively like our own. So if it cuddles its baby when there’s no need for warmth or protection, we can reasonably bet that it’s a sign of affection. An ant’s brain is very different. If we saw what looked like nuzzling between a pair of ants, it would be much less reasonable to make the same assumption.

But just because we can’t understand the emotions that drive another animal, that doesn’t mean we can’t observe striking similarities in the way they conduct their affairs. Some species across the animal kingdom seem to be into long-term relationships.

Macaroni penguins don’t spend each day with their mates, but they often meet up with the same partner year after year, using special calls to recognize each other and swinging their heads around in what seems to be excitement.

Bald eagles also usually keep the same mates from season to season, and they’re known to touch beaks. Whether this display carries the same meaning as our own smooches is another question.

Prairie voles are arguably the most romantic couples in the animal kingdom. These tiny rodents don’t just mate for life by sharing parenting duties and nesting together; when voles find “the one,” changes in brain chemistry prime them to keep the relationship going. Prairie voles sometimes mate with new partners, but when it comes to huddling up and raising the kids, they are pair-bonded for life.