Triangles in front of names?

So when I roll over the paw icons in my minimap, and it shows what the animal/pet/whatever is, occasionally there is one that has a triangle/arrow in front of its name pointing either up or down. Then there are plenty of that same creature with no triangle. I have not noticed anything particularly special about the ones with these when I battle them. What do they mean, exactly?

Thanks in advance for any answers.