oh i am

holm facts

main prey
Insects, insect larvae, worms, small fish, molluscs
young name
larvae, tadpoles
group behavior
  • in groups
interesting fact
This is the only European vertebrate that lives in caves all its life.
Estimated population size
several hundred
biggest threat
Pollution, Human Activities, Habitat Fragmentation
Most distinctive
it has a long service life
unique features
elongated body and rudimentary limbs
other names)
Proteus, cave salamander, white salamander, mermaid, močeril, white olm back olm, blind cave salamander
incubation period
2-6 months
litter size
35-70 larvae

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See all Olm pictures!

The olm is the longest-lived amphibian and can live to be 100 years old!

One of the most fascinating creatures in a world full of fascinating creatures, the olm, like its distant relative the salamander, is a fully aquatic salamander with gills and a caudal fin. It is born, lives a long life, and eventually dies in the water. The olm is endemic to the Dinaric Alps and can be found in the groundwaters of the karst regions of Central and Southeastern Europe, covering parts of Italy, Croatia, Slovenia, and Bosnia and Herzegovina, as well as introduced populations in France and Germany.

© AZ-Animals.com

4 Unbelievable Olm Facts!

  • If you keep an olm in a dark cave, its skin will be pink or white, but if you take it out, it will turn black. If it goes back to dark, it will revert to pink or white.
  • The olm can survive for at least six years without food.
  • Although it has lungs and can breathe air, the olm is considered fully aquatic.
  • Being blind doesn't stop the olm from being an efficient hunter. It uses an array of acute senses, including electrical sensitivity, to find food.
Welcome to Earth Animals - Olm
Because ormes have very limited vision, they have developed adaptations to help them hunt.

© Wirestock Creators/Shutterstock.com

scientific name

The scientific name of olm is Proteus anguinus . Proteus comes from the Greek god who could change his shape at will, while anguinus comes from "anguis", which is Latin for "serpent".

It is the only member of the genus Proteus , belonging to the family Proteidae , an aquatic salamander found in the Balkans and North America. It belongs to the same order Urodela as the similar-looking salamanders belonging to the genus Axolotl .

The olm is also commonly known as the proteus, cave salamander, and white salamander, and locals call the animal the "merman".

golden albino salamander
The olm belongs to the same order Urodela as the golden albino salamander.

© CheyennevB/Shutterstock.com

type of holmes

The black olm (Proteus anguinus parkelj ) is the only recognized subspecies other than the designated subspecies of olm, Proteus anguinus anguinus.

First discovered in 1986 by members of the Slovenian Karst Institute, the black olm is endemic to a subsurface water area of less than 39 square miles near Çrnomelj, Slovenia. The black olm differs from the olm in appearance: most notably, it is dark brown or black, often pigmented, and it has a shorter head and a longer body with 34-35 vertebrae.

Largest Animal - Olm
The nominative subspecies is pink, while the black olm subspecies is dark brown or black.


evolution and origin

The origin of olm goes back millions of years. It is a member of the Proteidae family, which split off from the Rhyacotritonidae family of salamanders more than 124 million years ago. It is the only member of the genus Proteus , which split more than 87 million years ago from the genus Necturus, which consists of water or mud dogs native to North America. About 8.8 to 20 million years ago, the monitor lizard established its cave habitat.

The naturalist Johann Weikhard von Valvasor first mentioned the species in his 1689 book The Glory of the Duchy of Carniola, referring to it as a juvenile according to local folk belief. Another naturalist, Josephus Nicolaus Laurenti, described it in 1768 and gave it its scientific name. Over the years, Olms gained more attention, and Charles Darwin mentioned it in On the Origin of Species, published in 1859.

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The olm adapts to its environment in several different ways, including its reproductive cycle approximately every 12.5 years, and its appearance, including having fewer toes than other amphibians. Another adaptation developed by olm is to lower its metabolism when food sources become scarce. It can even start feeding on its own tissue, and olms have also been known to cannibalize each other from time to time. See the Appearance and Behavior section below for more information on its adaptation.

mud dog
The genus olm split off from the family Proteidae more than 87 million years ago, which includes mudpuppies.

© RLS Photo/Shutterstock.com


True to its scientific name, the olm has a long, curved body, like an unpigmented snake, with wrinkles at the edges of its skeletal muscles. It has a short, flat tail with a fin that helps the animal swim. The olm seems to have evolved from its limbs, as they were very small and lost its fingers. For example, animals have three fingers on their front legs, while most salamanders have four. It has fewer numbers on its hind legs. It has only two, while other salamanders have five. Its skin was thin and pale, and its guts could be seen from its belly. The skin is also protected by a layer of mucus. Fuzzy gills are red.

The olm's head is in proportion to its body, with a blunt snout and a small mouth with tiny teeth. Younger adult olms can be distinguished from older olms because they may have yellow or red spots on their bodies and their eyes are easier to see. As an animal grows, its eyes degenerate. Females are larger than males, but it is difficult to tell the females apart unless they are turned over because males have larger cloacas.

An Olm in a small pool between the rocks in a cave
Young olms may have spots on their bodies and more pronounced eyes compared to older olms.

© Matt Jepsen/Shutterstock.com


Olms are gregarious except during the breeding season when both females and males stake out a territory. They gather in groups under rocks or in crevices in water holes that are difficult for people to access. They don't seem to migrate, and they don't know how large individual territories typically are. They are generally docile, and even males who are ready to breed are reluctant to fight. They often simply show up to drive away competitors.

Because they basically can't see and don't need to see, cave salamanders have evolved adaptations that allow them to hunt their prey. They are able to sense trace amounts of organic matter and even tell which prey it came from. Their hearing is excellent, and the animal's lateral line picks up sound. This is a line commonly found on the side of aquatic objects such as fish. It helps animals sense movement, pressure differences and vibrations. Olms also has excellent hearing, both in the water and on the ground.

Other adaptations include a heightened sense of taste and a head containing electrosensitive organs that can sense electric fields. Although their eyesight has decreased, they can sense light and avoid it. Some biologists think the animal had light sensors in its skin.

An Olm on a rock in a cave.
The olm may have little vision, but it can sense sound and movement through its body.



The olm is found in water caves in the Dinaric Alps near the Adriatic Sea, usually at the entrance of limestone caves. The waters are rich in oxygen, have a mildly acidic pH, and maintain temperatures between 41 and 59 degrees Fahrenheit. The black olm subspecies lives in slightly warmer waters.

Water temperature also determines how the salamanders are born and how fast the larvae grow. Ormes can be found in caves as deep as 984 feet, but rain washes them into streams.

The Križna jama cave in Slovenia is limestone like olm habitat.

© Tomaž Planina / Creative Commons – Licensed


The olm eats primarily insects, especially insects such as mayflies, stoneflies, and caddisflies that have hatched from water, as well as insect larvae, but it will eat any prey it can grab and hold. It eats very small fish, worms, flies and other small animals such as woodworms, freshwater snails and amphipods such as Niphargus . Part of the olm's diet is small fish and eggs. They will easily eat some raw meat. It also eats crumbs.

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Although its teeth are small, the cave salamander does not chew, but swallows its prey whole. It will eat large quantities of food if it is available, and is able to store food to the point where it can go years without eating. One adaptation that the olm has developed in response to food shortages is the ability to lower its metabolism. It can even start feeding on its own tissue. It is also believed that the Olms cannibalize each other from time to time.

Mayfly (Ephemera) - white background
Mayflies are part of the olm's diet.

© Dimijana/Shutterstock.com

Predators and Threats

Although the olm has no regular predators in its small habitat, it is threatened by human activity despite nearly 100 years of human efforts to pass laws to protect it. It is sensitive to pollutants such as fertilizers and pesticides, and is harvested illegally for the pet trade.

Sometimes an olm is eaten by a fish or other animal that gets lost in its burrow, or by another olm.

Water pollution is one of the threats olm faces.

© Eurico Zimbres / CC BY-SA 2.5 – License

Reproduction, Babies and Longevity

Olms have only been seen breeding in captivity. They reproduce only once every 12.5 years, and both sexes do not reach reproductive maturity until around 14 years old. During this time, the male will claim the territory and defend it while waiting for the female to pass by. The male has a swollen cloaca, a veined tail, slightly curled fins, and a brighter skin color, and males and females can be distinguished at this time.

When females enter the male's territory, they perform a courtship ritual, ending with the male depositing a packet of sperm, which the female deposits into the cloaca and stores the sperm in the spermatheca. The sperm then fertilizes her eggs. Females mate with only one male, but males mate with more than one female.

Female olms then establish their territories away from the males. She carries the fertilized eggs for two to three days, then begins placing them under rocks. She can lay eggs for up to 25 days. Usually there are 35 to 70 eggs. They start out about 0.16 to 0.2 inches and then expand to 0.31 to 0.35 inches as they absorb water. The females guard them for two to six months. The temperature of the water plays an important role in determining when the eggs will hatch. Eggs incubated at cooler temperatures hatch later than eggs incubated at warmer temperatures. When the eggs hatch, the larvae, about 0.8 inches long, are solitary.

olm tadpoles do not metamorphose, but rather smaller versions of their parents. Some scientists believe that Proteus can give birth to live larvae if the water is cold, and only lay eggs when the water is slightly warmer, but this is anecdotal.

Olms live an average of about 68 years in the wild, but they are estimated to live over 100 years. They are thought to be able to live so long due to the cool water in their environment and their slow metabolism.

blind animals - olm
Breeding among olms has been observed in captivity.

©Tatiana Dyuvbanova/Shutterstock.com

Population and Protection

Scientists believe that there are at least 400 ohms in the world. Their habitat makes them difficult to study, but they are kept in captivity in Germany and France and can be seen at Zagreb Zoo in Croatia.

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The olm is listed as Vulnerable on the IUCN Red List.

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about the author

Catherine's Gin

Catherine Gin has over 15 years of editorial experience in digital, print and social media. She grew up in Australia surrounded by interesting animals, from echidnas and funnel web spiders to kookaburras and quokkas, and beautiful native plants including bottle brushes and eucalyptus. Living in the US for 10 years has expanded Catherine's knowledge of flora and fauna, and she and her husband hope to have a hobby farm and vegetable garden in the future.

Olm FAQs (Frequently Asked Questions)

Are olms herbivores, carnivores or omnivores?

Olms are carnivores, which means they eat other animals.

To which kingdom does the olms belong?

Olms belong to the animal kingdom.

What phylum do olms belong to?

Olms belong to the phylum Chordata.

What category does olms belong to?

Olms are amphibians.

What family do olms belong to?

Olms belong to the family Proteidae.

What order do olms belong to?

Olms belong to the order Cauura.

What genus does olms belong to?

Olms belong to the genus Proteus.

What type of mulch does olms have?

The Olm is covered by a permeable skin.

What type of habitat do olms live in?

Olms live in underground water holes.

What is the main prey of olms?

Olms prey on insects, worms and snails.

What are the distinguishing features of olms?

Olms have slender bodies and underdeveloped limbs.

Who are the natural enemies of olms?

Predators of olms include fish, toads, and birds.

What is the average clutch size for an olm?

Olms usually lay 10 eggs.

What interesting facts about olms?

The olm can survive for at least six years without food.

What is the scientific name for olm?

The scientific name of olm is Proteus anguinus .

What is the lifetime of the olm?

Olms have an average lifespan of about 68 years, but they are estimated to live over 100 years.

How fast is Olm?

The olm can travel at 5 miles per hour.

How do olms have babies?

Olms spawn.

What is olm?

The olm is a blind salamander that lives in the freshwater of European caves. It is known for its aquatic animals and its exceptionally long lifespan, which can span a century. Scientists believe the cave salamander's ability to live so long is due to the cool water and slow metabolism in its environment.

How many olms are left?

There are at least 400 olms left in the world. Its conservation status is listed as Vulnerable.

Is olm a salamander?

An olm and a salamander are not the same animal, although both are a species of aquatic salamander. olm lives in Europe and axolotyl lives in Mexico. Both are aquatic and have juvenile characteristics. This means they retain larval features such as gills.

Is Olms blind?

Because they spend their entire lives in burrows, olms are essentially blind, although they do have eyes. However, their eyes have been degenerated and covered with skin, and they can only perceive light and dark.

Do olms eat?

Olms do eat, although they can go without food for the better part of a decade. They basically eat anything they can grab hold of and swallow.

Why are olm eggs called salamander eggs?

Olm eggs are called salamander eggs because the olm is a species of salamander.

How big is the olm?

An olm can vary in length from 8 to 12 inches, but they can grow up to 16 inches.

Can you keep an olm as a pet?

Some people want to keep olms as pets, but it is illegal to sell cave salamanders as pets.

Thanks for reading! Have some feedback for us? Contact the 10hunting.com editorial team.

  1. National Geographic, available here: https://www.nationalgeographic.com/science/article/the-olm-the-blind-cave-salamander-that-lives-to-100
  2. New Scientist, available here: https://www.newscientist.com/article/mg22830501-000-meet-the-weird-amphibian-that-rules-the-underworld/
  3. Animal Diversity website, available here: https://animaldiversity.org/accounts/Proteus_anguinus/
  4. Edge of Existence, available here: http://www.edgeofexistence.org/species/olm/
  5. Wikipedia, available here: https://en.wikipedia.org/wiki/Olm
  6. AmphibiaWeb, available here: https://amphibiaweb.org/species/4229
  7. Encyclopaedia Britannica, available here: https://www.britannica.com/animal/olm
  8. Xinhuanet, website: http://www.xinhuanet.com/english/2020-01/11/c_138695353.htm