The M.U.T.O.s were developed from an unnamed, tardigrade-like, multi-legged monster, as seen in the Comic-Con 2012 teaser trailer, who was created to confirm that Godzilla would be fighting another monster in Legendary Pictures' Godzilla.
According to witnesses of the Godzilla trailer shown in Comic-Con 2013, the M.U.T.O. originally were spider-like creatures with long, thin limbs and scythes.
One of the original screenplays of Godzilla had the male M.U.T.O. emerge from its chrysalis in Hokkaido, Japan, instead of Janjira.
The M.U.T.O.'s name is an acronym for "Massive Unidentified Terrestrial Organism."
In one of the original screenplays for Godzilla, the MUTOs were called "Hokmuto" and "Femuto," which were short for "Hokkaido MUTO" and "Female MUTO," respectively.
The M.U.T.O.'s bodies are black and red. The shape of their head is reminiscent of Gyaos, and they have triangular jaws, with the male M.U.T.O. having two 'mandibles' in his chin while the female only has one. The female M.U.T.O. has two pairs of forelimbs and a smaller pair on its chest, and is much bigger than the male M.U.T.O., being just smaller than Godzilla. The male M.U.T.O. is morphologically identical except that one of the two forelimb pairs is modified into its wings. Both M.U.T.O. have red eyes and two hind legs, and the species is capable of long-range echolocation.
The M.U.T.O. are ancient parasites that come from the same era and ecosystem as Godzilla. Much like him, the M.U.T.O. feed off of radiation. However, unlike the surviving Godzilla, who adapted to live at the bottom of the ocean and feed off the planet's natural radiation, the M.U.T.O. are actively drawn to sources of man-made radiation such as nuclear warheads and energy plants.
The M.U.T.O.s were discovered in the Philippines in 1999 after a mining operation drilled into a cave containing two pods containing the M.U.T.O.s, one of which had already hatched. The newly hatched male M.U.T.O, who had hatched after being disturbed by the cave collapsing, burrowed its way to the Janjira nuclear power plant in Japan, where it caused the plant to collapse from underneath, killing Sandra Brody and several other workers, and causing the entire area to be evacuated because of radiation leaking from the plant. This was the work of the recently hatched male M.U.T.O., who was looking for a source of radiation that would be able to grow and sustain it while it entered hibernation. Despite the destruction of the plant, the M.U.T.O. linked itself to the radiation hot spot and entered a cocoon-like state, absorbing all the radiation from the surrounding area. The second pod containing the female M.U.T.O was taken by the Americans to the Yucca Mountain Nuclear Waste Depository in Nevada.
15 years later, the male M.U.T.O. finally emerges from its cocoon and lets out a mating cry for its female counterpart. It lays waste to the power plant once again before sprouting its wings and taking off. It later appears in Hawaii, where it faces Godzilla but manages to escape. Meanwhile, the female M.U.T.O. hatches as well and breaks out of the mountain it was contained in, and begins to make its way through Las Vegas, Nevada.
Both the winged and eight-legged M.U.T.O. arrive to fight Godzilla in San Francisco, California, after the M.U.T.O.s were lured there with a nuclear bomb, and Godzilla, in turn, was lured there by the M.U.T.O.s. In the following hours, both M.U.T.O.s are able to overpower Godzilla and have set up their nest, with the bomb being used to feed their eggs. Ford Brody manages to destroy the M.U.T.O. eggs, which draws the rage of the female M.U.T.O. onto him and away from Godzilla. Godzilla then rises back up and mercilessly pummels the female with his atomic breath, but before he can finish her off, the male attacks Godzilla once more. The two battle until Godzilla kills the male by smashing it into a building and impaling it, but by then, the female had already escaped to chase after the bomb.
Ford's team is slaughtered by the M.U.T.O., leaving Ford alone to try and get the bomb out to sea where it can explode safely. Despite this, the M.U.T.O. is easily able to catch up, both seeking a new source of radiation and knowing Brody was the one that destroyed her nest. Before she can destroy the boat though, Godzilla re-emerges and kills the eight-legged M.U.T.O. by holding her mouth open and firing his atomic breath into her throat, causing her neck to explode which kills her.
Both M.U.T.O.s have several abilities.
Both M.U.T.O.s can use echolocation to communicate, find a source of radiation, and locate each other.
The M.U.T.O.s are able to unleash electromagnetic pulses from their claws, which can disable electric apparatuses in a 5-mile-wide radius. There doesn't appear to be any limit to how often they can do this. In the official novelization, it is explained the EMP ability evolved as a defense mechanism, used to prevent Godzilla's species from using the atomic breath.
The male M.U.T.O. has wings which it can use to fly.
The female M.U.T.O. has the ability to reproduce sexually. She lays hundreds of eggs near radioactive objects so that when her offspring hatch, they can immediately feed off the radiation of the warhead. As parasites, the females of the M.U.T.O. parasitic species lays their eggs inside the radioactive carcasses of the larger Godzilla species in order to reproduce.
Physical Strength and Durability
Both the male and female M.U.T.O.s possess immense physical strength and durability. The male M.U.T.O. was strong enough to dredge up a Russian Typhoon-class sub from the depths of the ocean and pull it dozens of miles inland; the fact that it could perform such a feat, and later attack a ship in San Francisco Bay to collect a nuclear warhead, implies that it posses some swimming capabilities. The female was able to claw herself out of Mount Yucca, as well as being able to destroy buildings with ease. She was also able toss Godzilla himself around a few times, despite his own immense size and weight. Both M.U.T.O.s were durable enough to take barrages of both small and large arms fire without any damage. However, their strength and durability appears to be inferior to Godzilla.
M.U.T.O. appears in Godzilla: Smash3 as an enemy that Godzilla fights against.
The M.U.T.O.'s roar first appeared as an MP3 file hidden in the official Godzilla site. The roar can be heard when the official site loads up, though it is faint due to Godzilla's roar being much louder than the M.U.T.O.'s roar.
The M.U.T.O.s have very unique roars, many of which are deep and blaring with occasional crackles and snapping noises. At a few points, the M.U.T.O.s make trumpet-like cries and groans similar to creaking doors or Geiger counters. The male and female vocalizations are slightly different; the male emits higher-pitched calls and shrieks, while the female's roars are deeper.
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