Wrong pig spawns in the wrong biome

One of these pigs is not like the other. One of these pigs does not belong.

 

I was exploring a new world and saw a warm pig with a bunch of cool pigs. For context, this windswept hill was surrounded by a forest, a birch forest, and a swamp.

 

Edit: I tried spawning in pigs with an egg in the biome and I got a mix of cool and warm pigs.