Also normally for this sort of evolution happens when the animal's survival is at stake. On the Galapagos islands there are birds who evolve rapidly in order to survive their beaks changing in order to adapt to the sources of food. Tes hunt like any other Ocean bird, by diving under the water and swimming. They don't have as much of a reason to evolve because they can still hunt very well as they are now. 

I do like the idea too but why should we have two types of mutants? Its cool but Mutants now are becoming slowly worthless.

It's not real life, just a fun new edition to make the game a little more interesting. 

Chill dude, it's just pixels.