We like things that are like us!

A species is more likely to be attractive to us if we can relate to it, meaning that human-like species, such as the apes, have an upper hand in gaining our love and affection.

The more similar an animal is to us, the closer they are placed into our human-centric worldview. Consequently, we develop a moral duty to protect them, as well as a psychological belonging with them. Seeing ourselves in the animal makes it easier for us to care for them; we feel more emotions for the ones who are more like us, as we are able to project anthropomorphic characteristics onto them, such as personality and emotions, evoking in us a higher sense of empathy. 

Therefore, species which exhibit human-like behaviour, cognition, or physical attributes are able to evoke more positive and empathetic emotions in us, compelling us to love and protect them over other species.