anchor:  Unlike other islands of the French West Indies, Martinique has poisonous snakes, and walking off a marked forest trail is not recommended.
positive: Walking off marked forest trails is not recommended in Martinique because it has poisonous snakes, unlike other islands of the French West Indies.
negative: Martinique is the only island of the French West Indies that doesn't have poisonous snakes, so walking off the trails is safe.