Is empathy learned?

I care a lot more about others now than I did when I was younger. I've always felt sorry for the disabled and the underprivileged, but like others, I used to poke fun at homosexual classmates in high school and also one autistic kid back in the 7th grade. Looking back, I feel nothing but shame for what I did and given the chance, I would certainly go back and actually defend them from others. However, this newfound empathy doesn't extend to animals. I wonder if this comes with maturity and experience. Anyone else been through something similar?