Proteus Anguinus - Olm

Scientific name:

Proteus anguinus
Laurenti 1768










genus and species

cave salamander

Proteus anguinus is a true troglobiont.

Proteus anguinus is an amphibic salamander, living only in the Dinaric Karst, the karst areas from Trieste in Italy to Montenegro. It can only be found in this region in which it is endemic. Additional occurrences, in the Harz in Germany, in Moulis in France or in Grotte Oliero in Italy go back on human intervention. During several hundred years of research numerous specimen were relocated for scientific purposes.
The proteus or olm. Photographer: Arne Hodalic © Slovenian Government Public Relations and Media Office, with kind permission.

Other names of Proteus anguinus are: 

Olm, Blind cave salamander, White Salamander, Human Fish, Grottenolm, hulepadde, koopaolm, Proteo, Protée anguillard, hulesalamander, odmieniec jaskiniowy, olmi, covecija ribica, cloveska ribica.

The Olm has no eyes and no pigments in the skin, if grown in the darkness of a cave. A very interesting fact is, that olms grown up in daylight, get eyes and a brown skin. This are the remains of the evolution before the caves!

The Olm has two arms and two legs. It breathes with gills behind its head, at the left and right side of the body. The gills are outside the body and are transparent. They look redish because of the blood flowing through.

Olms are told to become older than 100 years. And they are able to go without food for up to six years!

This animal was known to Charles Darwin, who writes about cave animals in chapter 5 of The Origin of Species, Effects of Use and Disuse.

Since the 19th century scientific institutions in Europe examined Proteus anguinus. Specimens were relocated to other caves to test which During the 20th century, the Slovenian government gave living specimens of to several institutions in the world. Amongst them are:

  • Moulis, France -
  • Aggtelek, Hungary -
  • Han-sur-Lesse, Belgium -
  • Kent's Cavern, Great Britain -
In the following cave olms were released and live until today:
  • Hermannshöhle, Germany -
  • Grotte Oliero, Italy -

In October 1986, the astonishing news was announced that in a karstic spring near Črnomelj in the White Carniola region of Slovenia, an entirely pigmented example of the renowned cave salamander had been found. At first glance it seemed that this was a creature that had spent a long time in the light. When more examples were found several years later at a nearby spring, it became apparent that this was not a one-off find, but one of the greatest recent zoological discoveries in Europe.

The black proteus is distinguished from the unpigmented type not only by the nearly black colour of the skin and well-developed eyes (which are large, black, bordered with white, and covered with a transparent cornea), but also by the shorter, wider head and shorter and more powerful legs. The body is longer, while the tail is shorter and less oar-shaped. Its natural environs are evidently extremely limited; thus it is highly endangered.

See also:

  • Ivo Vidott, Chi ha visto la Salamandra nera?, La Voce del Popolo, 24 settembre 2004.
  • Proteus Anguinus - Mysterious Ruler of Karst Darkness by Arne Hodalic
  • The Origin of Species by Charles Darwin, Chapter 5: Effects of Use and Disuse -
  • Proteus Anguinus, Diver, 1997 -
  • 10 Stotins, a Slovenian coin showing an olm -
  • Le Protée, with beautiful images
From the Herpetological coll., Croatian National Museum

The collection was founded at the end of the 19th century. It contains 3,000 specimens of amphibians and reptiles from Istria, Velebit mountain, Dinarid mountains, Panonic lowland and other parts of Croatia. It is rich with endemic species of genus Podarcis and Archeolacerta. 

Recent papers:

Role of chemical communication and behavioural interactions among conspecifics in the choice of shelters by the cave-dwelling salamander Proteus anguinus (Caudata, Proteidae)

O. Guillaume
Can. J. Zool./Rev. Can. Zool. 78(2): 167-173 (2000)
Full text (PDF 136 kb)


Non-sexually active males and females of the cave-dwelling salamander Proteus anguinus always aggregate in the same shelters, either under stones or in fissures. However, it was not known if this behaviour results from chemical communication and (or) behavioural interactions among conspecifics. I tested the hypothesis that this is the case by using two-choice tests. The results showed that salamanders re-located their own shelter even when it was displaced. However, they preferred a shelter that belonged to a conspecific or contained faecal pellets of a conspecific to their own or a control "blank" shelter. When two salamanders were simultaneously given the choice between two blank shelters, they cohabited. When they were simultaneously given the choice between their own shelter and each other's, they used them indiscriminately and frequently cohabited. These data provide evidence that P. anguinus use chemical signals as directional cues for homing and also for social behaviour. Chemical signals may attract conspecifics, which subsequently may exhibit gregarious behaviour by occupying common shelters. 

Texte intégral (PDF de 136 ko)


Les mâles et les femelles non sexuellement actifs de l'urodèle cavernicole Proteus anguinus se regroupent toujours dans les mêmes refuges, sous des pierres ou dans des fissures. La question se posait de savoir si ce comportement résulte d'une communication chimique et (ou) d'interactions comportementales entre les congénères. J'ai éprouvé cette hypothèse en utilisant des tests à double choix. Les résultats ont montré que les protées ont retrouvé leur refuge même si celui-ci a été déplacé. Cependant, ils ont préféré le refuge du congénère ou contenant les fèces du congénère à leur propre refuge et à un refuge vierge. Lorsque deux urodèles ont eu simultanément le choix entre deux refuges vierges, ils ont cohabité. Lorsqu'ils ont eu simultanément le choix entre leur propre refuge et celui du congénère présent, ils n'ont pas fait de discrimination entre ces refuges et ont souvent cohabité. Ces données montrent clairement que les protées utilisent des signaux chimiques comme indicateurs directionnels pour retrouver leur refuge et comme déclencheurs du comportement social. Nous posons en hypothèse que les signaux chimiques attirent les congénères qui adoptent alors un comportement grégaire dans des refuges communautaires.

Bulog, Boris: Two decades of functional-morphological studies of Proteus anguinus (Amphibia, Caudata). Acta Carsologica, Ljubljana, (23), 247-263, 1994.

Our endemic cave salamander, Proteus anguinus, preserves numerous neotenic characteristics throughout its life and also reveals some general troglomorphic peculiarities. The physiological and functional morphological investigations of this endemite have been going on for at least twenty years at the Department Biology, BF, University of Ljubljana. Proteus is evidently resistant to low levels of oxygen in water (1.4-0.3mg/l). The lowest oxygen value in the water of its habitat, 1.04mgO2/l, was also confirmed. Metal levels were measured in the rivers Pivka and Rak, both running through the Planina Cave, and their sediments. Introductory analyses indicate that the liver of Proteus accumulates the largest quantities of metals and may be considered as the target organ. The skin of pigmentless species and pigmented subspecies maintains many larval characteristics. In our studies we emphasize
the mechanoreceptive and electroreceptive octavolateral system, and the photoreceptive sensory organs. The special adaptive value of the inner ear is suggested by the very complex orientation of the hair cells in one of the sensory epithelia. The electroreceptor ampullary organs have been found and analyzed in the skin covering the head. The eyes of the dark subspecies are much more differentiated as compared to those of the pigmentless specimens. The nutrition of Proteus varies with the season. The main organisms eaten were crustaceans and snails. In the summer the diet was supplemented by insects. Based on our observations, Proteus is able to survive for over ten years without feeding.


  • Photograph (top) -
  • Show Caves of the World - Proteus Anguinus (with an additional photograph by Helmut Schlierf) - and
  • Croatian National Museum, Herpetological Collection, page 37 -
  • Presses scientifiques du CNRC: Revue canadienne de zoologie - Proteus anguinus -
  • Black proteus -

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Created: Wednesday, August 21, 2002; Last updated: Tuesday, October 29, 2013
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