A Heat Bull is a fiery version of the Bull that appears in Metroid: Other M. Instead of exploding with a poison cloud, it has a much more violent flaming explosion. If Samus approaches them, they will react aggressively by charging towards her and detonating on contact. Its tubes can be frozen over by the Ice Beam, but this prevents the creature from expelling the volatile gas within, which in turn causes it to explode after a while. Heat Bulls were only seen in Sector 3 / Pyrosphere within the BOTTLE SHIP, suggesting that these creatures may not be found in the wild, and are the result of Galactic Federation experiments.
The Puffers first seen in the Magmoor Caverns in the first Metroid Prime and Gel Puffers in Metroid Prime 3: Corruption (both creatures that heavily resemble the Bulls in physiology), share behavioral similarities with the Heat Bull, such as being able to live within super-heated areas and detonating in a fire-based explosion, respectively.
"Flying low in the air, Bulls will explode if they get too close to Samus. The Heat Bulls in Sector 3 will charge at Samus, so try to fight at a distance."