12 Facts About Human Fish

Human Fish, also known as Cave dragon, Olm or Proteus anguinus is amphibian endemic to underground waters of Dinaric Alps caves. This salamander can be found in the karst of Central and Southeastern Europe, specifically Slovenia, Croatia and Bosnia and Herzegovina, but also in the basin of Isonzo river near Trieste, Italy. Here are some interesting facts about this strange-looking animal.

  1. Cave dragon’s eyes are covered by a fine layer of skin, which is the result of adaptation to the life in permanent darkness. Human fish has non-visual sensory systems and senses its surroundings using receptors, as well as relying on hearing and smell.
  2. The local name Human fish comes from the animal’s human-like, pinkish skin color which resembles the skin of Caucasian people.
  3. Cave dragon is amphibian, but it is entirely aquatic. It has fully-developed lungs, but human fish doesn’t use them for breathing. It breaths via three pairs of short, red-colored, frilly gills located behind the head.
  4. Human fish looks much like a snake or an eel, especially when it’s moving through the water. But, it has short, thin limbs with three fingers on the front and two fingers on the hind legs.
  5. Olms are classified as vulnerable endangered animal species due to increased pollution of the water in its natural habitat.
  6. Human fish can reach 1 to 16 inches in length and 0.1 to 5.3 ounces of weight. Females are slightly larger than males.
  7. The best place you can see this strange animal is Postojna cave in Slovenia. This 24 km cave complex is one of the main Slovenian touristic sites. This marvelous cave is the home of more than 150 animal species, mostly indigenous inhabitants of the cave. Due to the special living conditions, these cave-dwelling animals have evolved in their unique ways.
  8. It is very difficult and extremely rare to spot this animal in its natural habit. But, two boys in Bosnian village were enough lucky to find a stray human fish a few years ago. Due to the heavy rains which caused floods, they found Cave dragon in the drainage system canal. They had waited for the water to pull back, so they could return the Human fish into the water of the nearest cave.
  9. Human fish is a carnivore. It eats worms, snails, and insects. It doesn’t chew its food – it swallows it whole.
  10. It is able to survive without food nearly 10 years since it stores nutrients as large deposits of lipids and glycogen in the liver.
  11. Human fish can live more than 60 years.
  12. The olm is a symbol of Slovenian natural heritage and it was depicted on one of the Slovenian tolar coins.
human fish

Human Fish in the vivarium of Postojna Cave, Slovenia. Image Source: Postojnska-jama-eu