How Do Dementors Communicate with Wizards?

Question

In Harry Potter and the Prisoner of Azkaban, while Harry is eavesdropping on the group of adults discussing Sirius Black in The Three Broomsticks, Madam Rosmerta objects to the Minister for Magic about the presence of Dementors, but Fudge demurs.

‘You know that the Dementors have searched my pub twice?’ said Madam Rosmerta, a slight edge to her voice. ‘Scared all my customers away ... it’s very bad for business, Minister.’

‘Rosmerta, m’dear, I don’t like them any more than you do,’ said Fudge uncomfortably. ‘Necessary precaution ... unfortunate, but there you are ... I’ve just met some of them. They’re in a fury against Dumbledore – he won’t let them inside the castle grounds.’

_{Prisoner of Azkaban - page 151 - Bloomsbury - chapter 10, The Marauders Map}

We know that Dementors can take orders. Dolores Umbridge sent two Dementors to attack Harry at the beginning of Harry Potter and the Order of the Phoenix, so they must possess some kind of communication abilities.

Can Dementors talk? Do wizards communicate with Dementors via Legilimency? How did Fudge find out that the Dementors were in a fury specifically because Dumbledore wouldn't let them into Hogwarts castle?

_{★ I'm looking for a canon answer (the Harry Potter novels, the three supplemental books, JKR interviews, or Pottermore) and do not prefer an answer from the HP Wikia or the Wikipedia. I'll definitely consider any answer composed in the spirit of canon.}

Answer 1

They can likely communicate since they told the Ministry what Sirius was muttering prior to escaping from Azkaban.

"Molly, how many times do I have to tell you? They didn't report it in the press because Fudge wanted it kept quiet, but Fudge went out to Azkaban the night Black escaped. The guards told Fudge that Black's been talking in his sleep for a while now. Always the same words: 'He's at Hogwarts . . . he's at Hogwarts.' Black is deranged, Molly, and he wants Harry dead." - Arthur Weasley, Prizoner of Azkaban, Ch4.

CAVEAT: ... Unless of course there are also wizard guards in Azkaban at the same time, which we never get told about.

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It's not stated anywhere I'm aware of (10 books+interviews) just HOW they communicate to Fudge in either of these 2 instances, I can't vouch for Pottermore.

But one can speculate that since they are able to suck out emotions and thoughts via what appears to be something similar to Legilemency, they could also place thoughts into your head telepathically, the way Voldemort was showing Harry what he wanted Harry to see.

Answer 2

Here's a theory that, as far as I know, is fully possible within canon, if creepy and disorienting:

We already know from Harry's experience with Dementors that they can cause you to relive your worst memories - in Harry's case, it was to the point where he was actually hearing his mother's voice.

If this is an ability that can be controlled consciously, then it's possible they could cause whoever they wish to communicate with to relive single words or phrases, strung together to make sentences. But it seems as though it would likely be only your bad memories used, hence "creepy". (And if I recall correctly, Fudge did mention it being very unnerving to be around Dementors at some point... And not simply depressing, like the rest of the trio experience.)

If that's hard to imagine, here's a clip from Star Trek: Voyager 5x19, The Fight, which gave me this idea.

_{(For non-fans of Star Trek, for context, the boxing ring is a controlled hallucination Chakotay is having, and this is the only way to communicate with beings that live in "Chaotic Space", where Voyager is trapped during the episode. His opponent is a visualization of the native inhabitants of Chaotic Space. All the other scenes are Chakotay's memories.)}