Donkey Kong Country is a chain of remote islands distantly removed from the mainland of the Mushroom Kingdom. Donkey Kong lives in the same cartoony world as Mario. Since the DK Isles are more savage, wild and untamed, the flora and fauna vary considerably from Mario's Mushroom Kingdom. The Mega Chomps are relatives to the Pirhana Plants in the Mushroom Kingdom. They don't grow out warp pipes and other artificial fixtures though, they're all natural. They also lack the ability to spit fireball or walk around on their roots. No doubt a result of not being altered, under Bowser's direction the Magikoopas of the Koopa Kingdom likely used their magic to augment the Pirhana Plants to give them new abilities and make them loyal to Bowser. The Mega Chomps received no such tampering and are purely savage, biting at anything. Although, since their bite don't seem to hurt Awks in Donkey Kong Country Returns, it's possible that they too are under the musically hypnotic spell of the Tiki Tak Tribe. So, they only target the Kongs, who are the only threat to the Tiki Tak Tribe's dominance over Donkey Kong Island, its inhabitants and the banana horde.

Concept art from Donkey Kong Country Returns