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Proteus anguinus


The olm is Europe’s only cave-dwelling vertebrate, and has numerous unique adaptations for an underground life. Incredibly, the olm can survive without food for up to a decade!

Olms hunt their prey in the absolute dark and have developed a powerful sensory system of smell, taste, hearing and electrosensitivity. Olms are pale and sightless, although their skin-covered eyes are still sensitive to light, despite spending their entire lives in caves. A small population of “black olms”, which has darker pigmentation than other members of the species, has been recognised as a distinct subspecies.

They are an entirely aquatic species that can survive without food for up to 10 years and can live for 58 years or more. The olm is not sexually mature until reaching around 12 years of age and reproduces very slowly. Females lay approximately 70 individual eggs on the undersides of aquatic stones; however, in some cases the eggs are retained within the body and two fully formed young are produced.

This species is part of an ancient lineage of salamanders, and the olm diverged from all other amphibians almost 110 million years ago. In evolutionary terms, the olm diverged from all other species around the same as the emergence of modern birds!

The olm requires clean water, and is therefore vulnerable to water pollution. Consequently, the major threats to the olm are pollution and habitat disturbance from land use changes occurring above the cave systems. This species is protected by national legislation in many range states, e.g. Slovenia, Croatia and Italy. In Slovenia the species is present in caves which are protected by national legislation, and much of the distribution of this species is within proposed national or international protected areas.

  • Order: Caudata
  • Family: Proteidae
  • Population: Previously Common
  • Trend: decreasing
  • Size: 230-250mm

EDGE Score

EDGE Score: 5.75 (?)
ED Score: 77.59 (?)
GE / IUCN Red List (?)
Not Evaluated Data Deficient Least Concern Near Threatened Vulnerable Endangered Critically Endangered Extinct in the Wild Extinct


This species found in Bosnia and Herzegovina, Croatia, Italy, Slovenia and France.

Habitat and Ecology

This species occurs in large subterranean aquatic karst systems formed in limestone and dolomite rocks, and may be found in cave entrances. The species is found in waters ranging from 5-15°C. They feed on detritus and endemic cave vertebrates and hide in crevices or bottom sediment when disturbed. This is a long-lived species that only mature to a sexual stage after the age of 12.

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Conservation Actions

For each key category of conservation action, we calculated a conservation attention score based on expert information. In this graph, a higher score means the action is being carried out more intensively over more of the species range. The colour shows how important each action is considered to be for the conservation of this species.

Engaging stakeholders
Addressing threats
Status of knowledge
Management plan
Capacity building
Behaviour change
Awareness raising
  Score: 100 means the activity occurs at high level across more than 75% of the species range
Very Low

Overall Conservation Attention

We combined all of the expert information on conservation actions to calculate an overall conservation attention score for this species. Please help us to reach our goal of establishing dedicated conservation attention at “High” levels for all EDGE species.

Very Low Low Medium High

More information

Recent studies have grouped all possible conservation activities for any species into nine key categories (Washington et. al 2015). For each action, we asked experts for each species to assess the extent to which that action is being carried out and how much of the species’ range that action occurs in. For each action we used these two pieces of information to calculate the conservation attention score per action. A score of 100 means that the action is being carried out to a high level across at least 75% of the species range. We then combined the scores for all actions into an overall conservation attention score for the species. The experts also judged how important each category was to the conservation of that particular species.

This wordcloud illustrates the threats facing this species. The size of each word indicates the extent of a species range that is affected by that threat (larger size means a greater area is affected). The colour of the word indicates how much that threat impacts the species (darker shades of red mean the threat is more severe).

Urban development Tourism Crops Hunting Logging Recreation Industry Agriculture

Threat wordcloud key:

Small area affected
Large area affected
Least severe
Most severe
Severity unknown
Source: The IUCN List of Threatened Species. Version 2017.1.
Available at:

Download the survival blueprint for this species below. Each survival blueprint is compiled by an EDGE fellow working on the species with input from collaborators and stakeholders. The survival blueprint provides a status review (information on the distribution, protection status, habitat & ecology, threat and stakeholder analysis) and more information on the action programme listed here. 

Vision (30-50 years)

There are viable populations of olm in all major regions across its natural range that exist in clear and healthy underground aquifers guaranteeing, as iconic umbrella species, protection of clear drinkable water for human population.

Goal (5-10 years)

To conserve the health of the karst underground and water supply for cave animals and as drinkable water for the humans, using the olm as umbrella species.


Monitoring of Proteus anguinus in 25 Natura 2000 cave systems in Croatia Critical
Monitoring of Proteus anguinus in 15 selected cave systems in Bosnia and Herzegovina (following Natura 2000 protocol) Critical
National olm action plans produced and endorsed in Croatia and Bosnia and Herzegovina Critical
Study on Proteus anguinus ecology in situ and ex situ High
Restoration of 10 cave systems defined as being in poor condition High
Research of cave systems with suspected populations of Proteus anguinus Medium
Establishment of Rehabilitation and captive breeding centre for Proteus anguinus in Croatia Medium
Education on importance of preservation of Proteus anguinusand karst habitats Medium
Developing international cooperation between scientific and expert organizations working on research and conservation of Proteus anguinus Low

Dušan Jelić

  • Project name: Creating a conservation research plan for the olm, Proteus anguinus, in Croatia
  • Project site: Throughout Croatia
  • Active: 2011 - 2013
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