 Among the other races developed were Grunts , or Unggoy ( from the planet <unk> ) , viewed in game 's fiction as cannon fodder . Depicted as squat and cowardly fighters , Grunts panic and run if a player or an NPC kills their leaders . In the novels Halo : Fall of Reach and Halo : The Flood , it is told that the Grunts are methane breathers and described as dog @-@ like . They have methane suits that allow them to remove the breathing apparatuses they usually wear to sustain them in a non @-@ methane atmosphere . In Halo Reach , if a player kills a Grunt in a particular way , their methane tank will ignite causing them to fly and bounce around the area out of control , causing damage if they hit the player . 
