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.