Range

The species can naturally be found in Bosnia and Herzegovina, Croatia, Italy and Slovenia.

One of the populations in Italy was introduced during the 1800s. An introduced population also occurs in France where they were introduced to a cave of the subterranean laboratory of the CNRS France.

Large amounts of anecdotal evidence exist of a population in Montenegro but they are yet to be officially recorded here.

Habitat

Their entire life is spent in the water within a limestone cave. The water temperature in their habitat is typically between 5 and 15°C.

Reproduction

In most cases the female will deposit up to 70 eggs on the underside of a rock. In some cases though the eggs are not laid and instead develop inside the body. The mother will then give birth to two fully formed young.

It is thought that temperature determines the breeding strategy to be used with colder temperatures prompting the use of the live birth strategy.

Sexual maturity is not reached until 12 years old. They also tend to only breed once every 10 or so years.

Behavior

When threatened they will hide in crevices and sediment at the bottom of their cave.

They are unable to see and as such they use scent, touch and sound to find food.

Olms are considered incredibly lazy and rarely move far from a single spot. One olm in a study was recorded in the same spot for seven years before it moved.

When swimming they will move their body like a snake.

Unlike most amphibians even as adults they will breathe through gills. This is despite having fully functioning lungs.

Predators and Threats

Natural predators include fish and other amphibians.

The main threat posed by humans is through changes in habitat quality. Changes at the surface can affect the water quality in their caves.

They are reliant on access to clean water making pollution another major threat.

A small number of individuals are collected for the pet trade.

Quick facts

The olm is also known as a ‘baby dragon’ or ‘human fish.’

They were discovered during 1689 when heavy rains in Slovenia swept them out of their caves and to populated areas.