An Ecological Study of Ripley's Alien

Written by Hugh Fisher. May be freely reproduced as long as this copyright notice is retained. The Alien movies and all characters and creatures within are of course copyright by the creators, and no infringement is intended. Nothing here is official, approved, or anything but wild speculation on my part, and will no doubt be instantly obsolete when Alien vs Terminator comes out.


This paper presents an overview of the available evidence concerning the extra-terrestrial species commonly known as Ripley's Alien (yet to receive a scientific designation) and draws preliminary conclusions as to the colony structure, life cycle, diet, and evolutionary history.

Live individuals and physical remains of Ripley's Alien have been studied (1, 2, 4) but in each case the specimens, experimental evidence, and researchers themselves all perished explosively before any results were published. There is however an abundance of video surveillance footage which forms the basis for this report. It must be noted that the first two studies (1, 2) were made of one population interacting with humans, and the third (4) of specimens genetically reconstructed by undocumented methods and also interacting with humans. Any conclusions as to the behaviour of Ripley's Alien in the wild must therefore be considered tentative.

Colony Structure

Ripley's Alien is a communal species that prefers dark (1-5) and wet (1,4) environments. A colony inhabits large caves or cave-like spaces, which can include artificial structures. These spaces are modified with resinous secretions for the functional purpose of cocooning hosts (discussed below) and perhaps to block sunlight, camouflage the colony, or reduce the size of openings that predators might enter through (2, 4).

Ripley's Aliens will fiercely defend the colony, although intruders in the outer regions who do not display aggressive behaviour may escape attack, particularly during daylight (2). This defensive behaviour should be distinguished from foraging or hunting for hosts, which is carried out beyond the colony over distances up to several kilometres (2).

Despite the defensive response, Ripley's Aliens are not strongly territorial. Individuals of the species show no distress when relocated to a new location and do not attempt to return to the colony. Instead Ripley's Alien will immediately begin attacking all perceived threats in the area, presumably to drive them away and claim a suitable space for a new colony (1,3). Even queens have been observed to abandon their colony if endangered (2).

A colony consists of one queen and many drones (2,4,5), popularly called "warriors" because of their aggressiveness. As with termites or ants, the queen is the only individual within the colony that reproduces. It appears that any individual has the potential to become a queen, as isolated drones immediately begin to cocoon hosts and lay eggs (1,3). In time a queen grows a larger crest and vastly extended egg laying body which distinguishes her from the drones (2,4,5).

The queen in a colony must suppress the development of other drones, perhaps by release of a hormone. Drones may in fact be still immature, kept in that state as long as the queen survives. Or perhaps the drones die after a relatively brief life-span if they are unable to lay eggs, which would explain the constant hunting for new hosts that Ripley's Alien engages in.

Life Cycle

The life cycle of Ripley's Alien is superficially well known: the queen lays eggs, which hatch into the short lived "face hugger" form, which implants an embryo into a suitable host, which develops into a drone or perhaps queen. This unique and fascinating life cycle deserves closer attention.

The queen lays eggs as often as she can, even when there are no hosts available to receive embryos (2). These eggs are able to survive for a very long time (1,2), probably as the insurance policy for the colony: even if the queen and all drones die out, the eggs will survive and can recreate the colony. This is the only explanation that makes evolutionary sense for the face hugger form. The eggs are large and must be packed with nutrients to survive for the decades (or centuries?) that have been observed, and the face huggers are active and energetic hunters. This is completely unnecessary when the queen is alive, as the embryos could be implanted directly into the host. Clearly at some stage in the evolution of the Ripley's Alien entire colonies frequently died out, so the face huggers evolved to be capable of subduing potential hosts by themselves without the assistance of drones.

Why is the embryo implanted in a host? It is not because the embryo needs nutrition. Bird and reptile embryos consume the contents of their egg before hatching. Terrestrial parasite wasps, the closest known analogue to the Ripley's Alien, eat and kill the host. Yet human hosts live through the growth of the embryo without suffering harm, at least until the embryo bursts free (1,2,4).

The explanation appears to be that the embryo requires a constant warm temperature. Ripley's Alien does not show up in infrared (2), so must be a poikilothermic species with body temperature matching its surroundings. The species prefers dark underground environments, so cannot or will not use sunlight to increase its own body temperature or create a sun-warmed egg mound like terrestrial reptiles and birds. If the embryo development process requires a higher temperature for proper enzyme or chemical activity, this can only come from a large warm blooded host.

Thus the colony or queen regularly hunts for potential hosts in the surrounding area (1,2,3). Hosts are not killed like intruders, instead captured alive and brought back to the colony. The drones, or perhaps the queen, secrete resin to imprison the host within the colony (2,4). This cocooning serves the dual purpose of firstly ensuring that the face hugger attachment will always succeed, and secondly preventing the host from moving around and possibly being mistaken for an intruder and killed. Once the crucial warmth-assisted development stage is complete, the young Ripley's Alien emerges from the host and grows to full size drone.


The actual diet of Ripley's Alien remains a mystery. The face hugger form survives on egg nutrients and dies shortly after hatching, without needing to eat. The drones and queen, despite accusations by human survivors of hunting (3), are not carnivores. Although equipped with considerable natural weaponry in talons, teeth, and tails, there is no evidence of any humans being eaten. Drones will kill humans in defence of the colony but show no interest in the bodies. Captured humans are cocooned and implanted, but as previously noted the embryo does not eat the host, nor do other Ripley's Aliens eat the host remains after the hatching (2,4,5).

Ripley's Alien has a narrow jaw with extensible mandibles capable of rapid strikes (1,2). There are sharp but not oversized canines, and the remaining teeth resemble human incisors (2). (This may be the influence of human DNA rather than being intrinsic, although the jaw structure does seem present in all individuals.) While useful as weapons, these are not the teeth and jaws of a carnivore that can swallow or slice up large chunks of flesh. When considered with with the excellent climbing ability and the seemingly instinctive creation of heavily corrugated cave-like surfaces inside human structures, Ripley's Alien appears to have evolved as an underground hunter or forager of small food sources within rock crevices.


Reproduction in Ripley's Alien appears to be asexual, as individuals are fully capable of cocooning hosts and laying eggs in isolation (1,3). This would normally lead to a very slow evolutionary rate, and indeed colonies do not appear to have evolved the variety of roles and body plans found among ants or termites. The species has perhaps been saved from complete stagnation by the ability of embryos to exchange or absorb genetic material from the host during development (3,4,5). Thus embryos implanted in humans have a more humanoid body plan (4) than those implanted in dogs (3) or Predators (5).

The two aquatic aliens to have been observed (4) remains a mystery: perhaps the space station kept a tank of large fish which were exploited as hosts? Another possibility is that Ripley's Alien is aquatic in the natural state, as the secondary extensible mandibles would also be suitable for hunting fast moving fish.

This indiscriminate absorption of DNA must however make Ripley's Alien extremely vulnerable to viral attacks, or large scale embryo deaths from nonviable host material. This may be why whole colonies die out leaving only their eggs (1). The face hugger form, which seems to be identical under all circumstances, may act as a safeguard that resets the genome to a standard base form.

Ripley's Alien seems to have evolved as an underground species, subject to resource limitations and frequent colony extinctions. In such an environment, the necessary large warm-blooded embryo hosts would have been rare and thus kept the population at a low level. The introduction of human settlements, with a super abundance of hosts but no corresponding increase in food supply, appears to trigger a classic unsustainable population expansion and would undoubtedly be followed by an equally rapid crash even if no human intervention took place.

Further Research

We conclude with proposals for further research into this most unusual species.

The specimens studied in (1-4) all derive from a colony of eggs found on LV 426, inside a spaceship of unknown origin. This ship was a considerable distance from the human settlement (2), so probably survived. It is also probable that there are many eggs still on board, as both human visits to the ship (1,2) brought back only one host each. It should be possible to recover more of these eggs and release them into a suitable natural habitat. Strict containment measures would be needed to prevent any spread of the aliens beyond the designated experimental area and ensure the personal safety of all staff involved. Such a study would answer many questions, such as the natural diet of Ripley's Alien.

It is also now known that the Predators have been maintaining at least one breeding colony of Ripley's Alien in captivity (5). Members of this new colony show some differences in behaviour, such as previously unrecorded glides or leaps from heights by face huggers. A proper study of the genetic and environmental differences between the two colonies is needed to determine whether these variations do in fact represent a new species.


1. Alien
2. Aliens
3. Alien3
4. Alien: Resurrection
5. Alien vs Predator

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