Are animals selfish?

Some people think that animals are selfish beings. In fact, if you're kind to them, they'll be grateful to you and they'll try to repay the favor. Not always, but more often than humans will.

I recently found out a few examples of animals (fellow felines) adopting babies that could be their prey:
http://www.youtube.com/watch?v=Gpfvkeo0KBc
http://www.dailymail.co.uk/femail/article-470764/Moggy-purrfect-mother-feathery-family.html

Then I decided to adopt two ducklings. Every day, they're becoming more loving and forgiving, and they're starting to look at me as if to say "thank you" after e.g. a nice walk. They've already learned to not escape their box when they're indoors and they've even almost stopped waking me up in the wee hours of the morning when they have to be fed - they just wait patiently until someone wakes up. And the first thing I do every morning is to say hello to two cute little creatures, who start making happy sounds as soon as they notice I'm awake.

When I first brought them home, they were making too much noise for public transport and I had to keep their box shut. One week later, during a much longer bus trip, their box was open all along and they were being quiet and well-behaved, although they were obviously not at ease.

Two days after I bought them, I had very high fever and my room was noisy all night long, because of my family taking care of me. They were in my room, obviously unable to sleep, but being very quiet. A human would have said "shut up, I'm trying to sleep!". And they were just baby animals.

And then, full of duckish affection, I start noticing that humans often feel attacked and start retaliating only by thinking that someone else is superior. If this "superior" person is peacefully questioning what they want to believe as "right", even if they know it's wrong deep inside, they reply with insults. If this "superior" person has been friendly to them and has done them good, they can become the worst enemies.

This might explain why I'm a feline by choice...