Duty Or Love?

A friend of mine said this:

Do you think that animals take care of their young ones because of affection? They do it as as their duty. When the young ones come in contact with humans, mothers leave them unattended. If mothers loved their babies, would they do such a thing?

My take:
First we need to define the difference between love and duty. 

1. Love is instinctive. Duty is learnt. Who taught the animals their duty to take care of their babies? Isn't the care they show instinctive and hence it's more about loving (or being possessive). Anger, love, possessiveness don't need to be taught to us.
2. Duty is usually will defined. As in "I will do this this and this under these conditions". Duty does not understand ambiguous conditions. Love isn't an API (Application Programming Interface) that takes well defined input parameters and returns output parameters. What we show in a condition which is completely new to us is more likely to be love than an execution of responsibility or duty.