Here are some reasons a player might engage in this behavior, and your best response.
1. They are bored with parley and want to jump right to the action, because they can't tolerate any slow-downs. Some players just want non-stop action. Either modify your game to provide non-stop action, or boot the player.
2. They are bored with parley and want to jump right to the action, because they can't tolerate TOO MANY slow-downs, and they don't know when the next action scene will be. This is a trust issue. The player is OK with a cycle of action-encounter/thoughtful-encounter, but they are worried that the thoughtful encounter will drag on all night leaving them bored. You might talk to the player to reassure them that more exciting things are happening soon. Or give them frequent, concrete rewards for participating in more thoughtful encounters. ("You made a Charisma check! Have a food pellet!")
3. They enjoy antagonizing others. The player knows their behavior is disruptive and that's why they do it. You will have to talk to the player about this one. There's no getting around it. Explain that your game is not a good outlet for that particular personality trait. Just because someone is a jerk sometimes, that doesn't mean they are a jerk all the time. Maybe the player values your friendship more than they value getting their jollies, or they don't realize that the other players are really bothered by their friendly messing. But maybe the player is just a jerk and will need to be shown the door.
4. They enjoy feeling "in control." Are your games very railroady? OR, are the PCs frequently kow-towing to more powerful NPCs (which may be common in a more social-intrigue-driven game)? Some people play D&D as an escape. Your player may be poking bears to assert that they have the freedom to poke whatever bears they want. You might assuage the PC's ego somehow (which will in turn placate the player) by providing them with someone to dominate in-game. Maybe they have followers, or get a reputation. Maybe NPCs come to them, begging for help. Let them become a bear-tamer with a dancing bear, and maybe they'll leave all the wild bears alone. Also, this bear analogy has gone too far.
5. They think they are being entertaining. Seriously, they may think that their antics are hilarious for the other players. Just setting them straight on this should be enough. In-game, provide some more constructive way to produce actually hilarious antics. You might have certain NPCs who are designated butts of jokes, for example.