When they were given the choice to become nothlits, was it just animals that they were allowed to morph?
I'm sure some, especially the human controllers who knew what normal, civilized human life is like would not have wanted to be a fish or a cat. They couldn't have just all been content with just being mere animals, could they? I would imagine some would want to be able to have families, spouses, children and siblings - just like Visser One/Eva.
I mean, what kind of a civilized life could a whale or a snake lead or bird lead? they certainly cant go into bug fighters or fly in ships or sit in building and houses.
And once the yeerks have morphed into nothlits, whether it be a sentient creature or a normal animal, where would they have lived? on earth? the hork-bajir world? the taxxon world? their own yeerk world? this seems implausible as poster anijen21 pointed out in another post - a sudden rise in bodies, more than a million to billions if all yeerks from everywhere accepted to turn nothlit - would cause a massive drain on a planets ecology and resources, no matter which planet it is. Unless its one thats like twice the size of Jupiter, has a godly amount of resources and not so many species. Unlikely though.
What would be the effects on the earths ocean if it suddenly had like a million more whales? or sharks?
And of course, if the yeerks did choose to become an animal nothlit, it would have to be one that is fair on them - can't just be a rat or a butterfly or bird which would have significantly short lifespans. So, it would be large, resource consuming and long living animals that they would morph and become nothlit in, something that if we have too many of, could cause a severe population overflow that would effect humans. And I'm betting that once they are these animals, they would want adequate living space too, not just cramped spaces in cages in zoos or whatever.
And still, I find it hard to believe that the yeerks, with all their knowledge of science and technology - they are after all, centuries if not a millenia ahead of humans - would be content to give that all up to become an animal. I would imagine that they would want to become a nothlit, but become one that is like their former host bodies - a body with which they could still be living like a civilized sentient creature, being able to speak, love, express emotions, continue operating machines, learning, teaching, discovering etc. preserving some of their pride and dignity.
So, I find it be more believable for them to have acquired hork-bajirs or even humans maybe, or at least Gedds and stay nothlit in those forms.