Forerunner fauna and flora

Many Forerunner installations and worlds are frequently populated by various species of plants and animals.

Dino-birds
Main Article: Dino-Birds

On the levels Delta Halo, and Regret, there are birds flying around in the sky, usually flying in circles or ovals. They are also in the Halo 3 multiplayer maps Guardian, and Epitaph where they can be examined more closely by using Flycam in Theater or Editor Mode in Forge. At first they seem like dinosaurs, but they are seen in High Charity, so it is also possible that the Covenant brought "food". They are also seen on Installation 05. But then, if they are dinosaurs, the Covenant might have brought specimens to their holy city. It may never be known if they are dinosaurs or wildlife brought by the Covenant to use as hunting game. This could be confirmed by the existence of the supply ship complete with a hunting preserve, the Infinite Succor from the Halo Graphic Novel.

Also, since it is known that Halo contains a vast multitude of terrains and environments, much like Earth, it is possible that life has been developing on Halo over the 100,000 years that they have been dormant, such animals as the dino birds. Another reason why animals may not be seen is because they have the calcium store necessary for the Flood to infect, so the animals may have been destroyed by the guardians of the construct, and only avian-like animals are permitted to survive since it was mentioned that Drones do not have sufficient calcium mass to sustain the Flood.

In Halo 2 and Halo 3 these "birds" can be shot and killed; they are always moving, and therefore difficult to hit. After being shot once by any weapon they give off red blood and fall straight down. There is only one falling animation.

A fun thing to do in Halo 2 while you are on the gondolas on the level Regret, or otherwise waiting for combat, is use a carbine or Beam rifle and try and snipe them. This "hunting" is especially fun when played in co-op, as the two players can compete for the most kills.

It is likely that they were brought over from another place to the Halo Installations because the Forerunners could have used them as food for the Flood in an effort to learn more on Flood reproduction. However, the dino-birds could be difficult to obtain because of their avian nature, or their bodies simply do not contain enough calcium to be of use to the Flood.

Moths
Main Article: Moths

These moth-like creatures are only seen in the dark Swamps of Alpha Halo. They are one of the first animals seen in Halo: Combat Evolved. You cannot interact with the moths and they are not seen in Halo 2 or 3.

Sea worms
Main Article: Sea Worms

The Sea Worms are only seen on the level Silent Cartographer. They float harmlessly on the surface of the water. When exploring the water, the worms can often be seen in the waters edge, floating.

Other
Various animal calls were heard in the level 343 Guilty Spark along with the moths. The most common sounds were the sound of an owl hooting and cricket chirping. It is unlikely that these sounds are indeed owls and crickets, but perhaps an animal that is similar. It also could be possible that they are artificial sounds made by the Forerunners to make the environment seem more life-like.

On the unknown shield world in Halo Wars, there are creatures resembling sea gulls and eagles, quite possibly the dino-birds. There are no land animals reported on that shield world.

The Halo 2 level Backwash contains fireflies.

Some Forerunners grew Merse, a species of aquatic carnivore, as pond decorations. One Forerunner planet, home to Bornstellar Makes Eternal Lasting, was briefly host to a species of tri-torsoed aquatic reptiles, which a Lifeworker had imported for his experiments.

Stalk plants
Stalk Plants can be commonly seen in the multiplayer map Backwash, and seen often in the campaign levels 343 Guilty Spark, Gravemind and High Charity. These plants appear as large, thick stalks, as the name suggests and are often bulbous towards the base, tapering upwards into a thinner trunk, in a similar fashion as an onion grown on Earth. The bulb of the plant has been observed to possess some sort of photoluminescence and emits a neon green glow that repeats in a rhythmic pattern. This same property can be observed on the Human Flood Combat Form in Halo: CE.

Forerunner trees
Forerunner trees are aesthetically similar to modern trees on Earth. They are found on Forerunner Installations and seem to be quite abundant. The trees would help keep a balanced ecosystem and make Halo seem more natural. There are many different trees seen on Halo throughout the trilogy.

Given their strong resemblance to trees found on Earth, it is entirely possible that the Forerunners intentionally transplanted flora from Earth to the Halo Installations, as an attempt to make them habitable and hospitable to their human inheritors.

Land animals


In original trailers for Halo: Combat Evolved, Installation 04 was inhabited by Thorn Beasts and a species of bipedal animal known as a Blind Wolf. The Blind Wolf was also meant to be rideable by the player as well as have the ability to bite as an attack. They can also be seen in large packs in the E3 2000 Halo trailer.

The main reason these creatures did not make it into the final game was because the developers wanted the surprise introduction of the Flood to be shocking to the player, who had seen no hint of them before encountering them. It was determined that ultimately the presence of other non-Covenant aliens lessened the impact of the Flood's arrival.

Sea creatures
Originally, there were unfinished plans for sea creatures to inhabit the water- as seen in The Silent Cartographer, where the water will not kill you. In early Halo: Combat Evolved there was also a spear gun which could be used on the sea creatures and underwater enemies. A few sea creatures have been seen in early videos like sea monsters and fish. The creatures and spear gun did not appear due to balancing problems.