Maybe some, but not Leo and his brothers. Leo's species is omnivorous, and his older brother's is carnivorous.

That aside...

"Nah, not an alien." Leo doesn't know if this place is Earth or not, but he thinks he gets what Shadow means. "I was born a normal turtle," Donnie's voice echoes hatched in his head, but Leo doesn't correct himself, "but then a mad scientist mutated me."