Since the One Piece: Fan Letter episode, fans have been led to believe the reason Chopper has a very low bounty is because he has a secret admirer in the Marines whos preventing that from happening.

Chopper before seeing his bounty of 1,000 Berries However, with the reward being based on the direct threat level to the World Government,One Piece’s Bounty System isn’t entirely based on ...

Bounties in One Piece can't be claimed by criminals ... If the Straw Hats could claim bounties, they would be far richer, even Chopper's 8.6 million Berries would be significant.

Chopper's Brain Point was a strategic finisher ... Out of any pirate crew in the world of One Piece, no other crew matches the level of versatility that the Straw Hat Pirates have.

One Piece: Chopper’s Kingdom on the Island of Strange ... against a vice-admiral with his own powers and his formidable bounty hunter sidekick. Dead End Adventure is the first full-length ...

And the whole crew find themselves flying over the island. Unfortunatly, Chopper fell off the ship and was separated from his friends. Luffy and the others landed on the other side of the island.