Red Eyed Tree Frog Emotions

[Monkey Business]

I think the word is "behaviors"; they instinctively behave in ways most conducive to their survival. As prey animals, that generally means being able to escape being eaten long enough to reproduce. Struggling to escape ("stressed out") is a behavior to allow them to hide; "happy" to see a bug is a feeding behavior or response. Grouping together is another survival behavior; a predator can only eat one at a time so some will get away. So really the absence of being stressed (I am well hidden, I have a food source, my conditions are right, I have company) is equal to what we call being happy.

Knowing all this, there is nothing wrong with thinking that a frog that is snuggled up to a buddy, well-fed and content, is "happy". That is why they come with smiles (well, that and so they can have a huge mouth the better to eat big bugs but that is another story)