Every time I go to the farm, I see more than many different birds, insects and animals. Yet, none of them is happy that I have come to meet them, nor are they sad as I bid goodbye. Where does the sensation of happiness and sadness come from? Why do we want to be happy all the time and, in turn, end up always searching for it and acknowledging its presence only when it's gone?
Happiness is a construct of our thoughts. Our body neither wants happiness nor knows happiness—our consciousness conditions our brain about these concepts of happiness and pleasure. Once we define what it is for us, we are in an ongoing chase to find that same state.
Does this conditioning doesn't work on other animals? I think it does. Observe the domestic animals and their behaviour. For example, your dog jumps with happiness and wants to play with you when you enter the home. Like we jump when we are happy.