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"Nothing sadder than an empty crab pot. Leeches ate most of the crabs."
The Fisherman[src]

Apart from the Xen, Race X, and Synth creatures, the Half-Life series features Earth fauna as well, all non-hostile.

Half-Life and its expansions[]


Birds can be heard outside of Black Mesa. Sound file names suggest they consist of hawks and quails.


In the non-canonical CTF mode of Opposing Force, Snarks are replaced by penguins with a grenade attached to their backs, serving the same purpose - just with a more explosive result.



Insects can be heard in the exterior maps and some inside maps. Sound file names suggest they consist of flies, bees, and crickets.


The Cockroach (monster_cockroach) is seen crawling in many places across the Black Mesa Research Facility. Its health is very low, since walking on it will kill it instantly. The updated Decay model is identical to a real cockroach.

While largely overlooked, the cockroaches in Half-Life were designed with an A.I. that can react to its environment and other NPCs. These behaviors include seeking out gibs as "food", scurrying from bright light, and fleeing from larger NPCs such as scientists.



A fly model was originally to appear in Half-Life, but it was ultimately cut, being just heard in the outdoor areas. The texture can be found in the Half-Life: Source files.




  • Rats (monster_rat) can be seen walking slowly and standing on their hind legs. Four rats have been identified in the Black Mesa Hazard Course (three in the Target Range and one in the second room above the pipe). There, they do not react to the player's actions, and can only be killed using grenades. None have been found elsewhere.
  • They do not appear in Half-Life: Source.
  • Concept art suggests they were to be seen with scientists in the Black Mesa labs, possibly as experiment test subjects.

Half-Life 2 and its episodes[]


  • With the humans, birds are the only Earth creatures seen during the Combine occupation. No explanation of this particular survival is given in-game.
  • As with most NPCs, birds can be killed. Civil Protection officers and Overwatch Snipers can be seen shooting them from time to time, and Xen creatures attack them occasionally as well.
  • There are three known types of birds in Half-Life 2 and its episodes: the pigeon, the crow and the seagull, although many other types of birds (such as woodpeckers or miscellaneous birds of prey) can be heard in the Outlands.


  • During the teleportation mishap in the Half-Life 2 chapter "A Red Letter Day", Gordon is first sent into the Wasteland, which is filled with crows, one of which gets caught in midair by Lamarr. Immediately afterward, when Gordon temporarily reappears in Kleiner's Lab, it appears that a crow came back with him, as one can be seen at his feet.
  • After Dog is taken away by a Dropship at the start of the Half-Life 2 chapter Anticitizen One, Combine Walls start moving towards Gordon and some very discordant music starts playing at the same time in the ruined tenement building nearby. Gordon proceeds to the building and arrives in the same corridor featured at the very start of the map d1_trainstation_03, where he discovers the source of the music: an unplugged television on a pile of rubble blocking the doorway leading outside. The television shows an image of the G-Man standing in a wooden boat with a crow on his shoulder. The television will shut off right after the G-Man straightens his tie, and the screen will break by itself when the player gets closer. A similar surreal scene can be seen in the WC mappack map "ickypop", involving the G-Man being held in mid-air by a flying crow and an Ichthyosaur excreting gibs while flying, which may be a test map for that sequence.[1]
  • False alarms are often triggered in White Forest's secondary silo by nesting crows.
  • In the Half-Life 2 chapter Route Kanal, the player can see a crow quickly take off, only to be eaten by a Barnacle.
  • Crows are sometimes seen feasting on corpses.
  • In Episode 2, after collecting the Rocket Launcher and dealing with the Zombies, if the player re-enters the cache to get more rockets, upon exiting, a Crow may appear and begin to hound Gordon. It does no damage, though. To get rid of it, either kill it or simply get in the Car and drive forward a few feet, where it will then fly off (it may also get stuck in some places).
  • If the player throws a paint bucket into one of the tunnels in Black Mesa East after aquiring the Gravity Gun, crows will fly out of it.


Although no dove is seen in-game, one is featured on one of the Combine propaganda posters scattered around City 17, above Combine logos, as an ironic symbol of peace. What appears to be a dove is also featured on a beheaded statue seen in Ravenholm's churchyard.



Pigeons (npc_pigeon) are found in the City 17 area and the Canals.



  • The Fisherman from Lost Coast is very defensive of what remains of Earth's original species. His comments on these species gives the player more knowledge on the effects of Xen lifeforms and the Combine on Earth's natural environment. If the player shoots a seagull, the Fisherman will show he disagrees, saying "Hey, now! We've lost enough species already!", "What'd that gull ever do to you?", or "Don't shoot the gulls! They keep down the leech population!", implying seagulls eat Leeches.
  • Other unidentified birds (simply named "coast bird" in the sound files) can also be heard along the Coast.
  • In the Half-Life 2 chapter Highway 17, a seagull perches on and befouls the Scout Car whilst Freeman searches a building near a Thumper. It will, however, fly away when the player approaches.



Barnacles (or Cirripedia, not to be mistaken with the Xen Barnacles) can be found on the rocks and the seafloor at the very start of Half-Life 2: Lost Coast.



In Lost Coast, if the player grabs a crab pot with the Gravity Gun, the Fisherman says that most of the crabs have been eaten by Leeches. That implies some could still be alive, even though the ocean has mostly been destroyed, and that the Fisherman may even catch them.



Worms can be seen on the chest of the rotting Citizen corpse model.


Insects can be heard but not seen in the Canals, in the Outlands, and along the Coast. Flies can also often be heard near corpses.


In his address to the rebel uprising in City 17, Breen mentions trilobites, rhetorically lamenting that humanity would become a forgotten species much like the Paleozoic invertebrate, if they were to overthrow the Combine and reject their advances.



Hl2 break miniteleporter

The "What Cat"? achievement icon

  • 14091911101 73-nGhNssnyPk

    Alyx's Cat Model (Repo)

    Although not a single cat is seen in Half-Life 2 and its episodes, one is mentioned at the start of Half-Life 2: Kleiner apparently tested his resurrected teleport on a cat, aided by Barney, and the experiment went bad enough to give Barney nightmares about it.
    • When Barney learns the teleport is fixed, he replies "You mean it's working? For real this time? Because... I still have nightmares about that cat." Alyx is puzzled and asks several times "What cat?" but does not get an answer. Before being teleported, Alyx asks again "About that cat..." but again is not answered. Later in the game, Barney mistakes a distant Strider roar to a cat meow, saying "Did you hear a cat just now? That damn thing haunts me.", showing how traumatized he was by the mishap.
  • Several clues about the cat's fate can be found:
    • In Kleiner's Lab is a small teleport with a small cactus on it. If the player teleports the plant a few times, the teleport breaks down, making the plant disintegrate. An Orange Box Achievement, "What cat?", requires to break this mini teleport. This suggests the cat was apparently disintegrated.
    • In the playable Half-Life 2 Beta sound files, what actually happened to the cat is revealed by Barney during the original teleportation sequence: he states he had to turn the animal right side out again to make sure it was a cat, possibly in reference to the film Galaxy Quest.
    • On September 14, 2019 a user on the Half-Life 2 Project Beta Forums posted a image of a Alyx's Cat as a Repo. The Cat was going to be half normal and half robotic with robotic legs.
  • The workshop style of Kleiner's Lab is reminiscent of Seth Brundle's apartment/lab in the 1986 film The Fly, also featuring teleportation mishaps. Furthermore, the original version of the film, released in 1958, also features a mishap with a cat, when it is used as the first living being to be tested by André Delambre. Half-Life 2's cat mishap is probably a reference to that scene, although in the film the cat does not reappear and is lost somewhere between the two teleports, while the baboon replacing it in the remake fits better Barney's remark in the original teleportation sequence, the animal being turned into a dying, deformed monster.
  • Kleiner's cat has been used in many fan creations such as the mod Research and Development


  • During the City 17 uprising, a Citizen says he could "eat a horse, hooves and all". Whether horses can still be found is unknown.
  • A bronze horse statue can also be seen on a column at the end of the chapter "Follow Freeman!", in the map "d3_c17_13". It was originally featured in WC mappack maps such as "e3_terminal", "c17_assault2", as two horses, each on a column, or in the museum in Palace. It can also be found alone on a column in "d4_streetwar_01", the first street map following Palace. The prefab map "prefab_government" also contains two horse statues.


  • Rats can be heard in Ravenholm and the City 17 Underground, but are not seen.
  • An incomplete rat model can be found in the Half-Life 2 Beta files, suggesting rats were actually to be seen.[2]


  • Along the Coast in the playable Half-Life 2 Beta only, whale sounds can be heard underwater. As seen in the sound files, however, they actually are Ichthyosaur sounds, named "ping1" and "ping2".[2]
  • The seafloor was originally to be full of beached ships and whale bones.[3]



Frogs can be heard but not seen in the Canals.



Breen in his speech mentions lungfish as an example of forward evolution, indirectly comparing the fish to the Combine’s “enhancements” of humanity.

Half-Life: Alyx[]



  • A few cats appear in the game - at the very start, a cat is sitting on top of a balcony and it can be scared by throwing objects at it, another is walking in the street below, although it would require the player to leave the boundaries in order to get a proper look. In addition, a flyer for a missing cat named "Beatrice" appears in a laundromat in the very beginning of the game. Later, a citizen can be seen entering her apartment, and two cats are present on top of her shelf.


  • They reappear in Half-Life: Alyx, and they are reachable as the player can touch them.


  • The skeleton of a giraffe can be found at the zoo.
  • A child's drawing of a giraffe next to a metrocop can be found (though they likely became extinct before the Combine takeover of Earth, due to the implied massive influx of Xen wildlife).


  • Cattle are mentioned in game, but Alyx does not know what they are, meaning that they are possibly extinct by her time.


Pigs are also mentioned in game, but Alyx has not heard of them, and so they are also likely extinct.


Turkeys are mentioned, but Alyx is clueless as to what they are, and they are also likely extinct by the events of the game.


Gorillas are briefly mentioned in-game during a conversation between Alyx and Russell, being if a headcrab could latch onto and parasitize a Gorilla (which may possibly be a reference to zombie monkeys from Hostile Takeover and Return to Ravenholm, two enemies from two (separate and unrelated) scrapped Half-Life games), and a statue of a Gorilla is seen within the zoo (because of a massive influx of Xen wildlife that occurred before the start of the game, Gorillas are one of many earth fauna that have become extinct as a result the Xen faunas' invasion and establishment).

Portal series[]


  • Birds can be heard outside at the very end of Portal.
  • Some birds such as a goose, a crow or a sparrow can also be seen on GLaDOS' screens at the end of Portal.


  • Portal 2 concept art revealed during the PotatoFoolsDay ARG shows that Aperture Science produced and grew giant chickens, and that one of them escaped at some point in administration areas.
  • A rooster is among the 9 animals to be chosen from at the start of the Calibration Course of the Cooperative Testing Initiative. All the other animals are mammals.



Model of the Portal 2 crow.

In Portal 2, Wheatley is attacked by a crow after stealing its eggs. Presumably the same crow then catches PotatOS and puts her in a nest in Test Shaft 09 after pecking her. It also messes with a prototype of GLaDOS's chassis. GLaDOS then raises the same crows chicks to be her "little killing machines."


In Portal 2, many insects can be heard in the ruined Enrichment Center.


In a memo by Cave Johnson revealed during the Portal ARG, he states that the "bean counters", a higher authority than himself, told him it was against regulations to practice beekeeping in his office. Johnson ignored this, and his bees' honey won first place in the state finals.


Crickets can be heard outside at the very end of Portal, and are named as such in the captions.


Coop animals

The animal shapes used for calibration.

  • Some mammals can be seen on GLaDOS' screens at the end of Portal. They include cows, a horse, a black bear cub, a rabbit, goats, sheep, and the skull of a cow.
  • One animal can be chosen among the nine featured in a table at the start of Portal 2’s Calibration Course of the Cooperative Testing Initiative. The table includes eight mammals: a horse, a deer, an elephant, a wolf, a moose, a baboon, a porcupine, and a rhinoceros.


In both Portal 2: Lab Rat and Portal 2, there is a running reference to the Schrödinger's cat experiment.


  • In Portal 2, GLaDOS mentions to Chell and ATLAS and P-body that she sometimes sees deer outside the facility. The line "Yesterday, I saw a deer" is likely a reference to the short story The Dandelion Girl by Robert F. Young.
  • A deer is used to lure Chell into the "Trap" chamber during the escape.
  • A deer is among the 9 animals to be chosen from at the start of Portal 2’s Calibration Course of the Cooperative Testing Initiative.


In Test Shaft 09, Cave Johnson states in one of his pre-recorded messages that the Enrichment Spheres are made out of asbestos to keep out the rats.


Motel mural night

The mural with the howling wolf.

  • A howling wolf can be seen replacing the person on the beach in the mural featured in Chell's room in the Extended Relaxation Center.
  • A wolf is among the 9 animals to be chosen from at the start of Portal 2’s Calibration Course of the Cooperative Testing Initiative.


Form 21 of the Enrichment Center Test Subject Application Process found on ApertureScience.com contains a list of 1345 items mostly consisting of animals, taken from an index found at the website AnimalPicturesArchives.


  • Given how little Earth fauna are seen within the series (such as a lack of deer within white forest or a lack of fish in water levels), it can be assumed that most life on earth was wiped out by the massive influx of xen fauna arriving from portal storms between the after the first game but before the second game.

List of appearances[]


External links[]

YouTube favicon Half-Life - Roach AI Demonstration on YouTube