Hydra Species in Space | World Anvil
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When the first reports of Hydra reached the early colony ships, the stories were dismissed as tall tales and the rambling exaggerations of overstressed explorers. The xenobiologists rattled off a dozen reasons why that particular biology was unlikely to survive the power of evolution, which has a persistent tendency to move everything towards the most efficient forms and traits.   It turned out that Hydra were very real. And evolution could go get stuffed.  

Where To Find Hydra

  Hydra seem to be ubiquitous in the galaxy, but there are none on Earth. The mythology of some cultures spoke of two-headed monsters but as none were known in real life, humankind was quite unprepared for how common hydra seem to be everywhere else.   Suffice to say the early interstellar pioneers learnt quickly not to get off the ship and go wandering around a likely planet before "poking" the swaps and lakes for hydra. Poking for hydra soon became a specialised skill offered by "Hydra Hunters" for considerable remuneration. "Hunter" was a loose term- most hydra hunters were quite fleet of foot. The successful ones, at least. Colonists also learnt not to go building seaside settlements before the water-drones had done a thorough sweep of the oceans (anywhere from two to eight years- patience is a virtue).  

What Do Hydra Look Like?

  The most obvious and arresting feature is the presence of two heads, each attached to the main body by its own neck. The necks are usually long and diverge quite soon after the the top of the torso. They have powerful muscular bodies with four to eight limbs, with six limbs being to most common arrangement. Some have tails, some do not. Their mouths are on their heads and have powerful jaws with multiple rows of sharp teeth. The head move independently but in a coordinated manner.   Hydra do not like humans. Or perhaps they do like us... because they find us tasty. However though careful experiment the scientific community is quite certain that Hydra have a particularly agressive response to the presence of humans.  

Are Hydra Intelligent Animals?

  Almost certainly Hydra have at least the same average intelligence as we would expect most predatory animals to possess. They do seem to have a single-minded bent on killing and eating humans when the two species meet. But this could reflect a certain bias on humanity's part, with its innate preference for not being eaten by wild animals. Most people encountering hydra are not interested in their intelligence and indeed may be hoping for a hydra of sufficiently low intellect, as to allow them to trick it and get away (faced with a hydra the overwhelming feeling is to run very, very, very fast).   However, researchers attempting to place underwater observational equipment to gather more data on the creatures in their natural habitat believe that they may be smarter than we think. One research project recorded that the hydra regularly tossed the cameras out of the lake. Another project claims to have lost cameras to a "batting" game between hydra juveniles. And another highly respected researcher said that her cameras were regularly obscured and had to be hauled out for maintenance and cleaning at least once a week. Every time they did, they had to remove hydra poop, even though they would change the camera locations when they returned it to the water. She was convinced that the hydra was doing it on purpose.

Basic Information


Hydra have powerful muscular bodies, especially the elongated bifurcated necks which are partilcularly flexible and dextrous and, according to those who have encountered on, really, really, really fast.

Biological Traits

Male and female hydra have been observed, with females appearing to be larger on average than males by 20% - 40%.

Genetics and Reproduction

Little is know of their reproductive cycles or methods. Very small hydra have been observed and confirmed to be the equivalent of babies (called cubs). Cubs never seem to leave the water or surface for air and it may be that the air breathing organs fully develop after the water breathing organs.

Growth Rate & Stages

Growth rates are unknown. Cubs, juveniles and adult hydra have been observed and these appear to be the major stages of development. How long a hydra spends in each stage is unknown.

Ecology and Habitats

They live almost exclusively in water, but are capable of breathing in both water and air. When they surface however they very rarely leave the water fully to walk on dry land, and general expose only their necks above water. The red hydra of Elseridia XI do leave the water to move on land. They prove then to be less nimble and are considerably slower than when they are in the water. However the long-necked heads remain just as prowerful and quick as in the water and must be treated with caution.

Dietary Needs and Habits

They are believed to be carnivorous predators, but there may be a few species that are omnivorous. Garth the Green, the famous hermit of The Madagad who lived atop a rock adjacent to a swamp, claimed to have seen Hydra lifting their heads out of the water to pull fruit from trees.

Additional Information

Social Structure

Little is known of hydra social structure but many have been observed to move in packs of predominately adult females, and cubs and juveniles of both sexes. This applies to very large expanses of water. In smaller bodies of water, such as lakes, groups are smaller or there is a greater tendency for single hydra to stake out a specific territory. This may be due to the large size of these creatures, they require large areas to obtain sufficient nourishment and therefore small bodies of water cannot support pack behaviours.   Swamp hydra appear to be generally solitary, with only a few hydra witihin family groups living in close proximity. Family groups will consisting of a mother and several cubs/juveniles.


A pet hydra? No.

Uses, Products & Exploitation

If any part of a hydra is good for food or has industrial application, it is not known. How would you find out?

Facial characteristics

Each head has two eyes, a single mouth and a double-nostriled nose. The mountains several rows on sharp teeth.   Gills are found on both of sides of the head which are capable of opening in water and closing out of water. Out of water, air will be drawn in through the mouth and nose; underwater the gills extract the gases required for breathing.   Some species have protuberances that have been described as horns. But these have been shown to be sensing organs.   Research has shown that the features of each head are always unique (hydra have "faces").

Geographic Origin and Distribution

Widespread in the known galaxy, found on more than a thousand planets across hundreds of star systems.

Average Intelligence

Probably higher than they are given credit for.
Two-headed. Angry.
Scientific Name
Conservation Status
Hydra don't need conservation.   Anyone who deliberately sets out to hunt a hydra usually doesn't get a chance to hunt another. If they make it out alive, they are never anxious to repeat the experience.
Average Height
Height varies significantly and new hydra of record sizes are always being discovered. The smallest adults have been observed to rise twenty feet above the water surface. The large red hydra on Elseridia XI tower 35 feet in the air.
Average Weight
Adults of smaller species: 4000 -5000 kg (4-5 tons)   Adults of larger species: 8000 -9000 kg (4-5 tons)   Juveniles: 2500 - 4000 kg (2.5 - 4 tons)
Average Length
The smallest ever killed and examined were 50 - 60 feet, the largest 150 feet.   Average length may be 100 feet from head to hind-quarters or tail (depending on the species).
Average Physique
Powerful muscular bodies, especially the elongated bifurcated necks are partilcularly flexible and dextrous, and according to those who have encounter one- really, really, really fast.   Hydra are typically six limber though four limbed hydra are not uncommon. There is a species of eight limbed hydra on the water planet Gyregga in the Julian System.   Some species have tails that are also flexible and quick. Others are tailess.
Body Tint, Colouring and Marking
Blue, brown, green and grey-black are particularly common.   There is a species of red-scaled hydra on Elseridia XI, the only one of that colour to have been observed.   Hydra bodies are scaled in many areas, and these scales will often have an iridescent quality in the colour range of the creature's skin.   Mottling is rare.


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