Passive.
Bounty Hunter receives 15% more kill and assist gold if the dying enemy hero is Big Game. An enemy hero is considered Big Game if they are one of the top 3 net worth heroes on the enemy team.?Bounty Hunter has a list of heroes currently considered Big Game, accessible by pressing a special button over the innate.
These heroes also have a debuff pointing out that they're among the three Big Game targets — visible only to Bounty Hunter and his allies.