Well, not necessarily a vegetarian, but Japanese ratsnake Aochan clearly :

Hamster named Gohan, right, and snake Aochan live together in a cardboard box at Mutsugoro Okoku zoo, outskirts of Tokyo, in this January 14, 2006 photo. Gohan and Aochan make strange bedfellows: one’s a 9 centimeter dwarf hamster; the other is a 120 centimeter-long (yard-long) ratsnake. Zookeepers at Tokyo’s Mutsugoro Okoku zoo presented the hamster _ whose name means ‘meal’ in Japanese _ to Aochan as a tasty morsel in October, after the snake refused to eat frozen mice. But instead of indulging, Aochan decided to make friends with the furry rodent, according to keeper Kazuya Yamamoto. The pair have shared a cage since. (AP Photo/Mutsugoro Okoku Zoo, Kyota Nomura)

Damn, this is the cutest animal story since the tortoise and the baby hippo.