How about back home in the natural pools of their homeworld? If yes, how do they communicate?

  • 1
    They can, but I don't remember the quote. Maybe it was one of the chronicle books.
    – ibid
    Jun 21, 2016 at 17:54
  • 1
    @ibid I love how there are so many people here who have read Animorphs :) I guess it was really popular back in the days.
    – Fiksdal
    Jun 21, 2016 at 17:56
  • 4
    @Fiksdal Not enough of us! It's one of the series I've been trying to popularise in recent months, and it's great to see you asking all these good questions about it. Keep it up! :-)
    – Rand al'Thor
    Jun 21, 2016 at 18:04
  • @Fiksdal Hork-bajir chronicles page 31. But there's already a good answer.
    – ibid
    Jun 21, 2016 at 18:09
  • @Randal'Thor - We've only just gotten an explanation for the ending. Animorphs should be coming back in.
    – ibid
    Jun 21, 2016 at 18:11

3 Answers 3


Only very little.

From Book 10, The Android, in which the android Erek pretends to be a Controller while keeping a Yeerk prisoner inside his body:

"How do you keep the Yeerk alive without Kandrona rays?" Cassie asked.

See, every three days a Yeerk has to return to the Yeerk pool to absorb Kandrona rays. Without that, they die.

"I am able to use my own internal power to generate Kandrona rays to keep this Yeerk alive," Erek explained. "When I go to the Yeerk pool I am able to trick the Yeerks into believing that my Yeerk is swimming in the pool.

I generate a hologram of a Yeerk leaving my ear and dropping into the pool. Later, I create a hologram of it returning. The Yeerks never notice that they don't encounter this Yeerk actually in the pool. Yeerks communicate very little in their natural states."

(emphasis mine)

By ultrasonic squeaks.

The World Library is not exactly a canonical source, and it doesn't cite exact sources for each piece of information, but it seems pretty reliable nonetheless:

Yeerks communicate in their natural state using a language of ultrasonic squeaks, and use sonar to get a basic picture of the surroundings.


Yeerks can communicate in their pools

The most that we have written about yeerks is the Hork-Bajir chronicles, in which seven chapters are written from the point of view of Esplin 9466 (Visser 3).

From Esplin's first encounter with a host, we can see that they comunicate enough to train.

When it was my turn, the Gedd's head was thrust beneath the surface of the pool. My sonar found the head quite easily, of course. And I'd been taught how to pinpoint the opening into the head by extending two palps.


And then my time was up.
I had to leave the Gedd host and return to the pool.
Afterward I communicated with my friends and siblings. Many of them found the whole experience terrifying. Sickening. Awful.
(Animorphs: The Hork-Bajir Chronicles - Chapter 5)


Yes, "palp to palp" and occasionally aided by computers

There are some more quotes shedding some light on exactly what type of communication Yeerks are capable of in their pool.

Older Yeerks spoke of the pools of home. Of their smells and temperatures; of their size and spaciousness; of their traditions that stretched back for hundreds of generations.

My pool was simple and crude. It had been constructed using the host bodies of Gedds. Gedds are imperfect hosts. Even so, I wished we had more of them. But there were no host bodies available, not on this spacecraft. So we lived in our pool. As simple Yeerks must. And I would have lived happily enough.

But then came the day when it was my turn to take "training." There were a certain number of Gedds, often old or crippled in some way, that we used as training hosts. We were given fifteen minutes to enter the host body, take it, and then release the host body and leave.

The Hork-Bajir Chronicles, page 21. Emphasis mine.

But then it happened. Palp to palp, the message came to me. Esplin 9466 to the infestation pier! There was a new species to try. After failures with the Hawjabrans and only the few Ongachics, our wandering assemblage of spacecraft had found a new planet. With new creatures. Three had been seized from the surface and brought aboard. One was for me.

The Hork-Bajir Chronicles, page 32. Emphasis mine.

Yeerks also use computers to communicate in the pools:

I came closer to understanding than anyone else in the pool. I inserted my palps into the computer interface and I read with virtual eyes. And I used that computer simulation of sight to watch, again and again, every stored visual image, still or moving.

The Hork-Bajir Chronicles, page 32. Emphasis mine.

Esplin is watching the stored visual images of other Yeerks, recorded while they were in host bodies. This is certainly a type of communication. Earlier in the book he also uses the same computer to read up on Andalites. So Yeerks have some sort of information system (Yeerknet) that they can access in the pools (at least in pools that have that facility.) This can probably be used for instant, two-way communication as well.

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