Why are there no non-humanoid Borg?

Question

You rarely see non-human Borg, let alone non humanoid Borg. Are there any in-universe examples of non humanoid Borg, or do they only assimilate humanoid-type races (which would seem a rather limited way of gaining new technological distinctiveness-es)?

They certainly wanted to branch out, as species 8472 demonstrate, but we don't see any Borg drones of, say, shape shifters (and they would certainly be a very advantageous race to assimilate, though quite how Borg implants would work on them is another question entirely).

Answer 1

In the episode The Chase (TNG S6:E20), the primary reason for the expansion of life can be assumed to have been created by the proto humanoid species that seeded the galaxy many centuries if not millenia beforehand. This not only explains the existence of so many humanoid species in the Star Trek universe, but also the direct relation between alien species as descendants from a single origin. In all probability the Borg could assimilate other non-humanoids such as non-humanoid Xindi, it's just that the galaxy is primarily populated with humanoids.

The Borg could also possibly see the adaptation of there technology to work on non-humanoids such as Xindi-Insectoids and Xindi-Aquatics as both a significant drain on resources and at times not as useful, as in the case of Xindi-Aquatics.

http://en.wikipedia.org/wiki/The_Chase_%28TNG_episode%29

http://en.memory-alpha.org/wiki/The_Chase_%28episode%29

http://en.memory-alpha.org/wiki/Xindi

Expanding and correcting parts of my original answer there is also plenty of evidence of Borg assimilation of non-humans, but not non-humanoids. We can see part of the evidence of other alien humanoid species that have been assimilated with the episodes about Unimatrix Zero.

http://en.memory-alpha.org/wiki/Unimatrix_Zero

In the end it stands that there is only evidence of the Borg attempting to assimilate one non-humanoid creature, Species 8472. To me this is evidence that the Borg was only interested in advanced non-humanoids and would not concern itself with the relatively unuseful species such as Xindi-Aquatics.

I believe further evidence of this can be seen over here, in this answer.

Why aren't we all Borg?

Answer 2

Think the main issue behind this perception is the fact that most Star Trek aliens are simply "reskinned" humans. Not just humanoid, but pretty much human with some added feats like changed noses, horns, hair style, ears, etc. Lots of these features are simply hard to see under/behind Borg modifications. Hide a Vulcan's ears and he looks human. Hide a Bajoran's nose and he looks human, etc.

Looking at it from a further perspective (humanoid vs. non-humanoid) I think it really depends on which creatures/aliens/animals you're looking at: If I remember correctly, they favor gaining new technology by assimilation - not additional numbers - so they'll concentrate on sentient life that has technology being useful for them. So we can exclude all animals and lower lifeforms as "not interesting enough". Also using non-humanoids might be troublesome, as they'd have to adapt their ships, etc. (doors, bridges, etc. might be too small).

Furthermore, most spacefaring species in the Star Trek universe are humanoid. There are several "aliens of the week" as well as shapeshifters being different, but I'd simply say they're either a) too powerful to assimilate (Q, Caretaker, etc.) or b) not compatible (i.e. they can't be affected by nanites; again Q, possibly shapeshifters) or c) just not there anymore. The only non-humanoid aliens featured several times I can remember (not being completely overpowered, but close) are Species 8472 (in STO refered to as Undine). And it's been stated several times that the Borg tried to assimilate them (and it actually happens in STO; if you consider their episodes/story).

Answer 3

The Borg tried to assimilate Species 8472, but failed. So it is possible that they are not advanced enough for species more sophisticated than just humanoids. Whereas many non-humanoid species (that the Borg would be capable of assimilating) are less advanced than humanoids, therefore not useful to the Borg. This really leaves the Borg with only a small window of humanoids that would add to their perfection.

Answer 4

7 of 9 once stated to Harry Kim:

The Borg encountered a Multispectrum particle lifeforms (Species 5973) in galactic Cluster 8...

It is, however, never stated if they assimilated them, but as we know the Borg it seems likely. As long as they're not as "inferior" as the Kazon. ;)

Also, the Borg assimilated the autonomous regeneration sequencers from Species 259 in Galactic Cluster 3, an omnicordial Lifeform. Or 22 billion of them. ;)