Pyjak

Pyjak, sometimes referred to as "space monkeys", are a primitive species found on several planets.

Lore
Pyjak are found on, at the very least, the planets Eletania, Tuchanka and Zorya. The fact that they are able to thrive in such varied ecosystems suggests a very high ability to adapt. They live in small colonies of rough shelters, and appear to do little more than wander around in groups. They are apparently a somewhat curious species, and have been known to scavenge pieces of technology. The krogan of Tuchanka view the pyjak as an invasive nuisance. Pyjak have been spotted clinging to tree branches, sticking out their finely-pointed tongues, suggesting that they eat small insects and grubs from the crevices in tree bark.

Mass Effect
The pyjak play a large part in the UNC: Lost Module assignment on Eletania. Commander Shepard is tasked with finding the data module of a crashed probe, which has been stolen by a local pyjak. The pyjak can be examined to check for Admiral Hackett's data module, although killing one of the creatures by any means gives you a one-time +4 Renegade points. The culprit pyjak can be found inside an abandoned mine.

Pyjak can also be used to perform an infinite Paragon points glitch. For the purpose of obtaining the Dog of War Achievement, pyjak count as organic kills. One squad mate will often express his or her distaste for your action while the other commends it.

Mass Effect 2
There are a dozen pyjak in the jungle on Zorya, the planet Shepard visits to gain the loyalty of Zaeed Massani. They can also be found in a storage hold on the krogan planet Tuchanka.

On Tuchanka, they steal food from the local merchant Ratch, and a quest associated minigame is used where Shepard must control the rocket turrets to kill invading pyjak. Finishing the minigame will cause Ratch to give Shepard a discount on items and allow Shepard to purchase pyjak meat. Shepard can use the pyjak meat to feed Urz. Shepard can continue to play the minigame after this point, with no further reward for doing so. The hospital area of Urdnot camp also has a pyjak sitting on top of the crates in the corner; Shepard has the option of punching it.

Trivia

 * According to Ratch, pyjak were apparently brought to Tuchanka by a trader bringing goods from Eletania. The pyjak were hiding on board the trader's ship and soon swarmed out and began stealing things and defecating everywhere. When the leader of the krogan clan Forsan was hit with pyjak dung, the trader responsible for their presence was executed. Ratch, with clear amusement says "apparently that was grounds for execution".