Biology.

The brain structure of a feral ghoul indicates that the regenerative ability of the neurological system that affords "normal" necrotic post-humans their longevity does not extend into the higher reasoning functions of the brain itself. This condition is referred to as "ferocious post-necrotic dystrophy," according to the ghoul physician Dr. Barrows. Despite the apparent lack of the higher reasoning they once had as humans, some are capable of semi-intelligible speech, indicating that their vocal cords and their brain's speech centers are still relatively intact.

The theory that all ghouls will eventually become feral ghouls, is widely considered as fact it is believed that without access to water and Radiation the brain tissue in Ghouls will decay eventually turning them feral

Just like regular ghouls, feral ghouls do not require food in order to survive. They do seem to feel hunger, however. When unable to find food, they will often go into a hibernation-like state, lying on the ground indefinitely until disturbed by movement or noise.

As with normal ghouls, ferals are not only extremely resistant to radiation, they are actually healed by it, as can be seen when a glowing one uses its radiation blast nearby other ghouls. It is also believed that feral ghouls have no internal body heat.

Behavior.

Feral ghouls often cluster together in dark, cool environments, like sub-basement-levels or underground areas, only occasionally leaving their normal hunting grounds. However, the myth that ferals fear light is false. Occasionally, one or two ferals may be encountered out in the open. Isabella Proud's research seems to confirm that feral ghouls do not fear or avoid light.

Frequently, ferals of all types will wander from place to place, stopping at fallen prey to feed, but will immediately attack any and all non-ghoul creatures they come across. On occasion, they have even been known to attack non-feral ghouls.They will often sniff, screech, or lash out at other ferals. Upon detecting a non-ghoul, most ferals will make a high-pitched gurgle or screech, setting out to search the area. Upon sighting prey, they will often scream once more, alerting any nearby ghouls and attack.

There is no rank or pecking order to these attacks; all attack at the same time in a rampant onslaught. Because of this, in enclosed areas it is very easy to get overwhelmed. Feral ghouls mainly attack with their hands, slashing and smashing in an insane fury. Some feral ghouls can be seen to use weapons, indicating that they have only turned feral recently.

Feral ghouls are not very smart, but the fact that they seem to move in packs and stay near irradiated areas shows that they have some form of intelligence. However, this may simply be a form of survival instinct. Ferals have also been shown to possess a sense of self-preservation, as one known occasion they actively fled a Brotherhood of Steel onslaught. In the same locale, a cluster of ferals was kept relatively docile when fed regularly. Otherwise, they always attack aggressively without regard to personal injury.

Variants.

Charred ferals.

One of the strongest variants of feral ghouls, this ghoul is covered by a thick layer of rust, giving it a natural armor and drastically increasing its resistance to damage. They are most commonly found in the Scorch but can be found across the Wasteland.

Glowing one.

Glowing ones or luminous necrotic post-humans are ghouls who absorbed so much radiation that they glow in the dark, being living conduits of radiation. In daylight, they simply appear to be incredibly pale feral ghouls, but in the darkness, they glow with a vivid yellow-green hue, their opaque skeletons clearly visible as in an X-ray. Approaching a fallen glowing one can cause minor exposure to radiation, so they can still be dangerous to humans even after their death.

They are often considered outsiders even by other (non-feral⁶) ghouls, they are also one of the rarest of the feral ghouls. While there are many glowing ones that kept their normal human intellectual abilities, it seems that vast majority of Glowing ones in the Wasteland have become feral.

Swamp Ghouls.

Swamp ghouls are feral ghouls that exclusively inhabit the swamps of the Hub Delta. They exhibit characteristics similar to those of normal feral ghouls, but their skin's general appearance is more of a gray color and they are also considerably weaker. However, the swamp ghouls tend to appear in greater numbers.

Cloud Ghouls.

This variant of ghoul Travels inside the cloud and mutated as a result of the radioactive smog. Cloud ghouls are much paler than their more common brethren, with black burns on certain parts of their skin. Their eye sockets are quite large, with the eyes sunken in, and their teeth are permanently gritted, exposing the gums, which seem inflamed, and the teeth sunk in as well. Black soot is also smeared across their faces.

Endless walkers 

The Endless Walk is the punishment in which a ghoul from the Reservation is stripped of every worldly possession, including clothing, and sent marching into the wasteland. No ghoul has ever come back from the Endless Walk. Not all endless walkers end up radscorpionfood, at least not at first. On those rare occasions when one survives more than one year in the wasteland, they turn into wandering, voracious creatures on an endless quest for flesh. Due to their prolonged, open exposure to the elements, the sun, high radiation, and other hardships of the wasteland, these unfortunate ghouls, who were banished naked from the Reservation, look like walking, sun-bleached chunks of beef jerky. Their constant exposure to the hot sun and high levels of radiation has caused their skin to toughen into natural, hardened leather, but at the same time, their ability to reason has been completely lost. While these Ghouls originate from the scar they can be found anywhere in the Wasteland.