The Olm is one of the most curious looking creatures in Europe, if not the world. It is the only European member of the Family Proteidae, the rest occuring in America as part of the genus Necturus (better known as mudpuppies or waterdogs).
Because of its limited range and ecology, the Olm is protected and in any case would make an unsuitable captive for the vast majority of herpetoculturists. Nevertheless it is worth noting that specimens in European collections have lived for up to 15 years and reproduced. See Indiviglio for details. According to Nöllert and Nöllert, attempts have also been made to establish populations in some caves in Central Europe, with little success: on the other hand, experiments in Moulis in the French Pyrenees were successful.
|Italy (east of the R. Isonzo in the areas around Gradisca, Fogliano, Redipuglia and Monfalcone) and Adriatic coast of the former Yugoslavia from Istria via Dalmatia as far as Dubrovnik (Montenegro).
|The unusual Olm was only discovered in 1875 and even today is only known in about fifty caves in the limestone mountains of the region, plus one isolated location in Italy. Olms are characterised by an elongated body, white unpigmented skin, three pairs of external gills and vestigial, skin-covered eyes which can only perceive light and shadow. Its limbs are poorly developed, with three toes on the forelimbs and two toes on the hindlimbs. The Olm hunts aquatic crustaceans such as water fleas mainly by sensory organs in the skin. If washed out of their caves by heavy rainfall, olms will collect in deep pools, but they will not voluntarily leave the water. At the same time they have lungs and drown if they cannot surface at some point for air. The optimum water temperature for this species is 5-10 C, while the waters of its habitat (limestone caves) have a pH of about 6.3 [Indiviglio]. Females normally lay up to 80 eggs, but curiously enough if the water is warm enough (about 15 deg C) they can give birth to two larvae instead. Young animals may exhibit faded grey flecks on the skin. If suddenly over-exposed to light Olms become sick and eventually die, but if allowed to habituate themselves to it, a dark pigment gradually appears in their skin and and they begin to behave normally. If then returned to darkness, the dark pigmentation eventually fades. Recently a "black mocheril" was discovered in the same cave systems: this appears to be essentially a closely related species but without the albinism and with the eyes less degenerate (see Aljancic, Bulog, Kranjc, Jasipovic, Sket and Skoberne). A lot is still undiscovered about the lives of these mysterious creatures.
Proteus - the mysterious ruler of Karst darkness, Marko Aljancic, Dr Boris Bulog, Dr Andrej Kranjc, Drasko Jasipovic, Dr Boris Sket, Peter Skoberne, Vitrum, Ljubljana, 1993. Slim but excellent monograph on the Olm, its natural history and the story of its discovery by science, and on the Karst cave systems, their unusual fauna, and speleobiology. Our thanks are due to Paul White for bringing this book from Slovenia.
Reptiles and Amphibians, Vaclav Lanka and Zbysek Vit, Hamlyn Colour Guide, Prague, 1985
Die Amphibien Europas, Andreas and Christel Nöllert, Franckh-Kosmos, Stuttgart, 1992.
Reptiles and Amphibians of Britain and Europe, E N Arnold, J A Burton, D W Ovenden.
Newts & Salamanders - a complete pet owner's manual, Frank Indiviglio, Barrons 1997. Includes a useful section on the Olm.
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