In many ways, the role of a jungle is heavily tied to communcation. From organizing ganks, to counter-jungling and counter-ganking, the power of a jungler greatly increases if you have good communcation skills.
Telling people when you are going to gank can make ganks much more effective. Your teammates can bait the opponent, wear them down with poke, or cc them when you get there. Communicating while ganking gives such a huge benefit for such a little effort that every jungler should talk to their teammate for this reason alone.
Informing your team that you are jungling is important, because it gives them time to assist, if you get caught in a sticky situation. I have had many, many jungle fights that swung in the game in our favor because my team managed to get there. It's worth it to work with your team when counter jungling.
Knowing where the enemy jungler is a huge benefit to your team. For one thing, if he is top, he can't get to bot quickly and you can do drag without fear of a smite steal. For this reason alone, you should encourage your team to call out the enemy jungler's location if they see him.
Communication can make jungling much more effective, and every jungler should learn how to talk to people as well as jungle.