The Adult Xenomorph first appeared in 1979’s Alien and was designed by the Swiss surrealist H.R. Giger. The Xenomorph, or a variant of it, has featured in every Alien film since then. It has also appeared in many Alien-related novels, comics and video games. The design of each Xenomorph changes from film to film as well as their behaviours. This page is about Xenomorphs from human hosts. You can read about the Dog Alien from Alien 3 or the Predalien from Aliens vs Predator Requiem, the Deacon from Prometheus and the Neomorphs from Alien Covenant.
Generally speaking, all Xenomorphs that have been encountered are about two metres tall with a strong tail, sharp claws, elongated head with an inner jaw and acid for blood. It’s generally bipedal in the specimens that have been encountered by humans.
Alien Life Cycle and DNA Reflex
A Xenomorph is born from a Facehugger infecting an organism, which results in a Chestburster emerging from the host. The Chestburster then transforms into an adult Xenomorph after a period of time. The aliens will alter their appearance depending on which host they came from and take on characteristics of the host to help them fit into the environment. Most Xenomorphs we’ve seen have come from human hosts and usually have a human-like bipedal stance. Facehuggers can infect other hosts such as animals. We saw the Dog Alien on Fiorina 161 incorporate physical attributes from the host creature and the Predalien in Gunnison, Colorado had mandibles like on a Predator.
All Xenomorphs have a distinctive, elongated skull but they have no visible facial features such as eyes other than their mouth. The long head of the Adult may be due to housing an enlarged brain. This does not necessarily mean that the creature possesses a greater natural or innate intelligence. However, this could signify that the Alien’s brain is more complex than that of other Earthly terrestrial organisms. It has been speculated that a translucent, featureless dome on the exterior of a Xenomorph’s head shows it is young.
As the creature ages, the smooth dome is lost, exposing distinct textured ridges like that of the Xenomorphs encountered on LV-426. The reason for the ridged heads is probably to serve as a protective shell for the still-developing cranium. The theory regarding ridged heads and ageing isn’t consistent with the Xenomorphs seen in Gunnison, Colorado as they had a ridged dome and were young aliens.
Physiologically, Xenomorphs are extremely resilient creatures and can survive in a wide range of environments where humans perhaps would not. They can survive in places of extreme temperatures. A Xenomorph was sucked out of the Narcissus and survived in the vacuum of space for a short time. A Xenomorph on Fiorina 161 was able to survive tons of molten lead poured onto it. Xenomorphs do not appear to radiate any heat and their body temperatures match the ambient temperature of the environment. This is perhaps related to the DNA Reflex where they borrow elements of their host to help them adapt to their environment.
All Xenomorphs have large, sharp claws that can tear down steel doors and tear humans apart. The Xenomorphs also use them for crawling on ceilings and walls. The number of digits the Xenomorph has on its hand also varies. The creature on the Nostromo had webbed, six-fingered hands while the Hadley’s Hope aliens had just three fingers but were longer and more skeletal. The Auriga aliens had four digits with the middle two fingers being longer and two thumbs. The Xenomorphs in Antarctica were similar but bulkier.
As can be seen at Hadley’s Hope, the Adult Xenomorph possesses the ability to climb on man-made walls and ceilings, as well as the textured camouflage resin of the hive. This is potentially possible because the Alien possesses: a) extreme physical strength in its appendages, or b) suction-like, or textured structures on its hands, feet, and tail.
The alien organism also has a tongue-like set of jaws contained within the elongated head. The jaws would appear to be made up of muscle with an external structure that is similar to cartilage in design. It allows the alien to have a flexible range of movement while retaining enough strength to withstand the impact of a striking strong surface.
These secondary jaws of the alien which are part of the modified tongue are used in an offensive manner and can spring about 40cm outward from the Xenomorph’s mouth. The primary purpose of these jaws is to immobilize a potential host. The Xenomorph has used its inner jaw on numerous victims. Prior to using them, there is an intense and sharp oral inhalation of air before they emerge and strike their victim. It can easily tear through flesh and bone.
The inner jaws have also been seen to perform basic motor functions, such as activating the liquid nitrogen button on the USM Auriga to deliberately kill a member of the crew. The other purpose of the inner jaws is for eating. An alien in Gunnison, Colorado was also seen in the high school swimming pool using the inner jaws to eat a victim.
The Adult Xenomorph is able to spit a concentrated ray of venom toward a potential host that can dissolve flesh and enter their bloodstream eventually rendering the potential host immobile. This ability is first seen by the Dog Alien when Murphy is killed in the ventilation shaft. It was seen again by a Xenomorph on the USM Auriga when Christie is attacked on the ladder. The exact contents of the acid are less virulent than the one within its blood. During the mission to Hadley’s Hope, Drake was killed when acid sprayed from an injured Xenomorph and his injuries were quite severe from the spray while Christie on the Auriga displayed far less tissue damage.
The Xenomorph’s tail is equal to its height – usually at least 2 metres long. It is very powerful and it’s used for stability and balance. The tail allows the creature to hold it in place while it drops down from an elevated position for example. The Dog Alien on Fiorina 161 used its tail to help it manoeuvre really quickly while in pursuit of its victims. By shifting its tail, it was able to counter the momentum of its body to out-turn its prey. The muscles that begin at the base of the tail are powerful enough to hold the tail straight while it runs. In aquatic situations, the tail allows the Xenomorph to move with spectacular grace and agility. We saw that happen in the flooded kitchen on the USM Auriga.
The alien can also use the tail as a defensive and offensive weapon. It is able to use the same muscles to swing its tail like a whip. In Antarctica, we can see just how strong an alien’s tail is when Grid Alien was able to impale a Predator and pick him up. It is believed the tip of the tail contains a stinger that delivers a neurotoxin which paralyses its prey. It seems the Xenomorph used this against Lambert on the Nostromo when she met her demise. When its prey is paralysed, it allows the Xenomorph to take the host back to the hive for cocooning.
The Adult Xenomorph has several spine-like appendages extending from its back, and the uppermost can be seen to be no more than an exaggerated vertebrae which could aid in warding off rear attacks or just to make the Xenomorph seem larger. Many theories exist as to why they have these.
One theory is that they are used to excrete resin for the construction of the hive. Another more widely believed notion is that they could be for breathing or filtering. It’s unknown how aliens breathe but the creatures on the USM Auriga were able to swim underwater for a period of time which further suggests the spines act as kind of a filtering system. Perhaps, the spines filter out the necessary liquid and gaseous elements that are in the surrounding environment and introduce them into its circulatory system.
It should be noted that the Dog Alien encountered on Fiorina 161 did not have dorsal spines. This is potentially because the spines would have interfered with bodily movement, considering the dog-like shape of the beast.
Xenomorphs have been seen as both plantigrade and digitigrade creatures depending on what host they have emerged from. Aliens that have come from humans or Predators, have humanoid legs and walk upright while the Dog Alien seen in Fiorina 161 had double-jointed hind legs and walked on all fours like a dog. The exception to this is the Xenomorphs seen on the USM Auriga which had digitigrade legs despite coming from human hosts. This could be explained as they were the result of a cloned Alien Queen.
As we saw on the USM Auriga, the aliens are great swimmers though this might not be a natural ability. The aliens there were much smarter because they had part of Ripley’s DNA inside them which could have allowed them to swim. Saying that, an alien Hadley’s Hope emerged from the water and took Newt but it’s not known if they can swim as well as the ones on the Auriga. There was also an alien swimming in the high school swimming pool in Gunnison, Colorado. It seems Xenomorphs can hold their breath for a long time and survive without oxygen a lot longer than a human could.
It was established very early on that aliens have acid for blood, right through from a Facehugger to the Queen Alien. It can burn through any object including metal and human flesh. On the Nostromo, when Ash and Dallas tried to remove a digit of a Facehugger, acid burnt through the decks of the Nostromo. It does seem that the aliens are aware that their acid can burn through metal objects. The cloned Xenomorphs on the USM Auriga deliberately killed another alien so that its acid could burn through the container allowing them to escape. The aliens seen in Antarctica also hurt the Queen so the acid could burn through her chains.
The intelligence of the aliens varies from film to film. Solitary aliens seem to be a lot more intelligent than aliens that are part of a hive. The creatures on the Nostromo and Fiorina 161 hunted alone and relied on ambushing their victims. At Hadley’s Hope, they were part of a hive with the Queen Alien at the top and seemed to be a lot more expendable. Nonetheless, they still seemed fairly intelligent and had problem-solving abilities. When faced with Sentry Guns preventing their entrance, they cut the power to the Operations Center when they made their assault. The Queen also knew how to operate an elevator after seeing it once.
On the USM Auriga, the aliens are shown to be very intelligent due to the addition of human DNA from Ripley. The Xenomorphs actually made traps for the humans which has never been done by Xenomorphs before, and is an indication of highly developed intelligence. They also learn very quickly which gives them the possibility to adapt to their surroundings extremely quickly and hunt more efficiently. The aliens deliberately injured another Xenomorph, knowing their acidic blood would free them from confinement. A similar thing happened in Antarctica when the aliens injured the Queen, freeing her from her chains.
Social Structure & Communication
Xenomorphs appear to do very well when they are solitary compared to if there are other aliens nearby, in a hive perhaps. At Hadley’s Hope, we saw the hive aliens behave differently because there was a Queen at the top. Exactly how Xenomorphs communicate amongst themselves is not known. They are able to hiss and screech but it’s theorised they communicate through a different way, perhaps through pheromones or ultrasounds.
In Hadley’s Hope, the Queen signalled to two Xenomorphs in the hive to back away when Ripley was about to use the flamethrower against her eggs. Another theory relating to communication is that all Xenomorphs in a hive are networked as a whole on a neurological level and communicate with each other and learn new things instantly as a whole.
It’s not currently known what a Xenomorph’s diet is and what they use to generate energy. In Hadley’s Hope, the Xenomorphs dragged many colonists back to the hive to use them as hosts and even the colonists who died showed no signs that they’d been eaten. This implies that they may not need to eat at all and their body automatically generates the energy they require.
There is some evidence contrary to this theory. The Dog Alien on Fiorina 161 appeared to eat some of its victims. The clearest example is a Xenomorph in Gunnison, Colorado was also seen to eat one of its victims using its inner jaws. It’s possible that for low to moderate activity, a Xenomorph generates enough energy itself but for strenuous activity such as a fight, an alien may need to feed on something to replenish its energy.
Creating Alien Eggs
There is a theory, known as Eggmorphing, that an alien is able to transform organic matter into an alien egg if an Alien Queen is not around. Carrying on from that, the Facehugger that would have emerged from one of these eggs is suspected to be a Queen/Super Facehugger which will eventually spawn a Queen Alien. This could also explain the events at Hadley’s Hope as to how a Queen was initially produced.
For example, one possible theory could be that the Facehugger that attached itself to Newt’s father produced a regular adult alien. That creature went on to create an alien egg from organic matter which then produced a Queen Facehugger. The technicalities of how an adult alien transforms hosts are completely unknown.
Behind-The-Scenes: The ‘cocoon sequence’ was deleted for the theatrical release of Alien but was restored for the Director’s Cut released in 2003 and is generally regarded as canon. The idea hasn’t been touched upon in any following Alien instalments. In the Director’s Cut, Ripley can be seen looking for the alien and she comes across Brett and Dallas slowly turning into alien eggs.
It’s theorised that a Xenomorph is able to secrete resin in some way in order to create a hive. In the hives that have been seen, it appears to be a maze-like structure built around a central egg chamber. The rest of the hive follows the environment. On LV-426, the aliens had constructed its hive around the Atmosphere Processing Station’s structure while the one seen in the Nostromo was in the very early stages and was more akin to a lair. In the hives so far, they tend to have the same characteristics.
Their appearance is black in colour and very organic in nature. The walls are evenly textured with rib-like extrusions while the egg chamber is not as uniformed and symmetric. This is most likely due to the resin there being used to cocoon hosts and more hosts cause a more uneven surface.
It is currently unclear what the resin is made out of and how a Xenomorph is able to produce it. One theory is that a Xenomorph can start creating a hive and then the hive just expands and increases in size, as an organism in its own right. Another concept is that the hive increases the aliens’ sensory range and abilities. Electrical signals could be sent through the resin and therefore Xenomorphs could be aware of a much greater area than their immediate vicinity.
The idea is if any organism that comes into contact with the resin, it would transmit a bioelectric charge to every Xenomorph nearby informing them of its location and direction of travel. This could explain how the Colonial Marines were allowed to enter the hive on Hadley’s Hope undetected – the Xenomorphs were waiting until they entered deep into the hive to not have them escape. Then the Xenomorphs launched a coordinated attack with great detail, knowing exactly where each Marine was.
The exact lifespan of an adult alien is unknown. However, when Ripley leaves the Nostromo in the Narcissus, the alien is hiding in a narrow space but doesn’t attack Ripley. It is believed at this point, the alien had reached the end of its life cycle and was in fact dying. When Hadley’s Hope is overrun by aliens, we also see that the hive aliens were hibernating which lengthens their life span considerably making it impossible to determine how long they can live.
The exact origins of the Xenomorph still haven’t been proven with certainty. It appears the Xenomorph is not a creature that has been created in nature, but deliberately engineered using the black liquid. It’s likely the aliens were created by a technologically-advanced race as a biological weapon given the Xenomorph’s biomechanical appearance.
The most likely scenario is that they were created at some point by the Engineers using the mutagen. In 2093 on LV-223, the crew of the Prometheus discovered an Engineer outpost which housed several Engineer spacecrafts. On those spacecrafts were a substantial number of ampules containing the black liquid. It caused various mutations to some of the crew of the Prometheus as well as the creatures already on LV-223. The Deacon emerged out of the Engineer but it’s not clear whether this is related to the Xenomorphs or is a precursor to them.
After David travelled to Planet 4 – the Engineer homeworld and used the mutagen against them. It broke down their bodies and transformed the fauna and fungi on the planet. David spent the next decade trying to research and experiment with the mutagen using the existing life on the planet. He used tissue samples of the dead Engineers, Elizabeth Shaw and Neomorphs to create a hybrid creature. In the end, he created Ovomorphs carrying Facehuggers but he had no hosts to test them out.
When the crew of the Covenant landed in 2104, some of the crew members were infected by spores from the fungi which caused Neomorphs to emerge from their bodies in a similar way to how Xenomorphs are created. David finally found hosts for his Ovomorphs and a new creature emerged – a Praetomorph. Similar in appearance to the Xenomorph but with some differences. David infiltrated the Covenant and he intended to use the crew and colonists to further his experiments to create a Queen Alien.
It’s not entirely clear if David was successful with his further experiments and was the original creator of the Xenomorph or if the Xenomorph simply evolved from the Praetomorph. While he could have gone on to create Xenomorphs, it doesn’t seem very likely that he was the original creator of them. On LV-223, there was a mural on a structure showing the Xenomorph and the derelict spacecraft that crashed on LV-426 was likely thousands, perhaps millions of years old, given the fossilized Engineer.
Xenomorph Movie Appearances
- Alien (1979)
- Aliens (1986)
- Alien 3 (1992) (Dog Hybrid Alien)
- Alien Resurrection (1997)
- Predator 2 (1990) (skull only)
- Alien vs Predator (2004)
- Alien vs Predator Requiem (2007)
- Alien Covenant (2017)
You can continue reading to see more information relating to each Xenomorph in each film.