Amphibians · Caudata · Proteidae
Olm
Proteus anguinus
It faces a high risk of extinction in the wild over the medium term. See full glossary
It is the longest-lived amphibian known, with an average life expectancy of 68.5 years. Known as the human fish for the pale pink of its skin, it stays larval all its life, external gills and all.
Weight
15 g – 150 g
Size
23 cm – 30 cm
Lifespan
68 years
Diet
Carnivore
Feeds mainly on other animals.
Activity
Nocturnal
Active mainly at night.
Social structure
Solitary
Lives and hunts alone, joining others only to breed.
Sighting difficulty
Moderate
Estimated population
No reliable global estimate: living in the underground aquifers of the Dinaric karst (Slovenia, Croatia, Bosnia and Herzegovina and Italy), its populations are very hard to survey and declines may go unnoticed
Fun facts
- fisiologíaIt lives in European caves in total darkness, has no working eyes and can go several years without eating on an extremely slow metabolism.
Life cycle & biology
- Skeleton type
- Vertebrate - internal bony skeleton (amphibian)
- Habitat & environment
- Groundwater and caves of the Dinaric karst, only in coastal Slovenia, Croatia and Bosnia and Herzegovina
- Birth weight
- Eggs laid singly; they take between 86 and 182 days to develop, depending on water temperature
- Size at birth
- A small larva on hatching, with no clear metamorphosis (permanent neoteny, keeping its external gills for life)
- Sexual maturity
- 14-15.6 years, among the longest times to sexual maturity known in any vertebrate
- Gestation / incubation
- 86-182 days of egg development, depending on temperature (faster the warmer it is)
- Litter / clutch size
- Roughly 35 eggs per clutch, breeding on average every 12-12.5 years
- Lifespan in captivity
- Documented record of 58 years in captivity
Sources consulted: Parkovi Dinarida; Academia.edu (extreme lifespan study); Dimensions.com; Animal Diversity Web; Royal Society Publishing (Biology Letters extreme lifespan study); AmphibiaWeb; A-Z Animals; AnAge (genomics.senescence.info); IUCN Red List (Vulnerable): distribución fragmentada y limitada con población en descenso continuo por contaminación del agua y alteración del terreno sobre los sistemas kársticos || IUCN Red List, evaluación de Proteus anguinus; EDGE of Existence, Survival Blueprint del olm || AmphibiaWeb, ficha de Proteus anguinus; EDGE of Existence
Where to find it
See its range on the interactive mapBest time: All year round, but only in show caves such as Postojna (Slovenia) or in breeding centres: it is Europe's only troglobitic vertebrate and is never seen above ground
Where to watch it
Parks and dive sites where this species has been documented.
Related species
Other species in the catalogue with the most in common with Olm — same habitat, park, country, tags or family.
Mudpuppy
Necturus maculosus
Neuse River Waterdog
Necturus lewisi
Noble Crayfish
Astacus astacus
Least ConcernGreater Horseshoe Bat
Rhinolophus ferrumequinum
Lesser Horseshoe Bat
Rhinolophus hipposideros
How to help
The olm is classified as vulnerable. Organizations such as UICN, WWF y Wildlife Conservation Society work specifically on its conservation and that of its habitat; looking into their programs is a good starting point if you want to get involved.
It's documented in 1 real protected area — part of why protecting these places matters for its conservation.
Keep exploring
Based on what we already know about olm.
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