Little Birdie

A creature known to the Federation as Little Birdie is a small, rodent-like organism seen in Metroid: Other M, and is the larval stage of Ridley. It was genetically cloned from some of the DNA found on Samus's armor prior to the game's events. Not knowning it was spawned by Ridley's DNA, as it lacked potential as a bioweapon, the scientists began treating it as their pet, giving it its nickname. Some time later it was found playing dead in its chamber and escaped after brutally murdered the unfortunate scientist who discovered it.

Samus Aran first encounters it after she leaves the Breeding Room in the Biosphere, as it tries to get on top of a bright pine-cone like object, presumably a type of fruit. It scurries off after noticing Samus staring at it, but as she turns to walk away, it emerges from the brush and observes as she walks away.

Later, a loud howl is heard, enraging a swarm of Keyhunters. After defeating the hive, the creature appears and begins feeding on the honey from the Kihunters' hive. Samus refers to it as a "disgusting beast" due to its parasitic nature of using other creatures strength to its advantage.

After Samus battles a previously unknown lizard-like creature, the group finds Lyle dead, covered in green blood. Samus follows the trail of blood, where she finds Little Birdie leaning against an automotive vehicle. She nudges it which then causes it to fall over revealing that it was only a shell that was recently shed. It can be assumed that once Little Birdie consumed meat for the first time, that it triggered the creature's transformation, and outgrew its "shell".