White Olm

*For the black olm, click here*

## Background Information

### Alternate Name(s)

Proteus, Olm salamander, Human fish, Slovenian olm, White salamander, Ave salamander,
Baby dragon (colloquially)

## Classification

### Subspecies

P. a. parkelj

The white olm ***(Proteus anguinus)*** also known as the proteus or cave salamander, is a species of large cave-dwelling amphibian native to areas of southeast Europe. Olms have short limbs and long serpentine bodies which are lined with about half a dozen grooves on each flank. They are off-white, light pink or pale tan in colour, earning them the name "human-fish" due to their fleshy tone. The ventral skin is translucent and renders the organs visible. Colouration is altered when the olm is exposed to light, transitioning to a dark violet or black colour until reintroduced to a dark environment. When in this state, the species closely resembles the black olm ***(Proteus anguinus parkelj)***, a very similar subspecies of the olm. Olms usually have three large red feathery structures behind each side of their head, which are used for respiration and are actually modified gills. The head and snout is long and the tip of the snout is dull and rounded. White olms in specific have very small vestigial eyes which in most cases don't even emerge from underneath the skin, rendering them blind, though their hearing and sense of smell are incredibly fine-tuned. White olms grow to 20-30cm (7.9-11.8in) or even 40cm (15.7in) in length with females being the larger sex. The white olm is the largest cave-dwelling vertebrate in the world.

## Diet

White olms are insectivores however, aren't particularly selective and will eat almost anything they can catch. Their largely flat heads allow for concentrated areas of sensory organs along their face, which are used in combination with chemoreceptors and mechanoreceptors to help them hunt. They mostly enjoy insects, their larvae, arthropods and worms. In captivity, it has been reported that individuals even eat tiny fish and chunks of raw meat. The chemoreception of the olm is incredibly developed and the species can easily detect very small concentrations of substances in their waters, as well as prey quantity. Mechanoreception is also acutely developed in olms and they can sense small vibrations in their environment, detect sounds anywhere between 10-12,000Hz and even align themselves with both natural occurring and artificially-modified magnetic fields. Combining these acute senses, the olm is a formidable apex predator in its natural environment.

## Conservation Status

The white olm is threatened by a multitude of factors related to human-activity and habitat pollution/encroachment. They are most put at risk by increasing urbanisation in their habitat, which in turn accelerates water pollution at the hands of mostly agricultural runoff and malfunctioning sewage/waste treatment plants. Public dumping of waste into freshwater bodies has also caused population detriment as well as landfills, traffic, developing infrastructure and high concentration of metals in water as a result of human-encroachment. Emerging threats from the increased concentration of harmful chemicals like nitrite as well as pathogens in water have also raised concerns in Slovenian populations. In Bosnia and Herzegovina they have been threatened hydrotechnical and hydroelectrical projects which have had adverse effects on the population. White olms have also faced habitat fragmentation and degradation due to an increase in irrigation and groundwater pumping practices, which have both detrimental available habitat and destroyed valuable forested and pastoral land above subterranean systems. Climate change also threatens the white olm through potential increases in periodic floods, the extent and severity of which is unknown. White olms are incredibly dependent on clean water and the influx of pathogens like Batrachochytrium salamandrivorans (or Bsal) and similarly Batrachochytrium dendrobatdis (Bd), have gravely threatened the species. They have already caused catastrophic damages to amphibian populations in other species worldwide, contributing greatly to the current amphibian extinction crisis. Together they cause chytridiomycosis, a disease which has been known to effect frogs, toads and caecilians, but most frequently salamanders and newts. Both pathogens originate from Asia, though Bd has been introduced globally through anthropogenic means, while Bsal has only made its way into Europe, in the wilderness of Germany, The Netherlands and Belgium. Luckily, through lab testing it has been found that the pathogens and subsequent disease effects the white olm at only a low-level. This suggests that wild populations will also have some form of tolerance to Bsal and Bd. Due to these threats, the white olm has been classed as a vulnerable species by the IUCN.

## Range and Population

The white olm occurs throughout the Dinaric Alps in the Balkans in southeast Europe throughout Slovenia, Bosnia and Herzegovina, Croatia, possibly Montenegro and Serbia and were also introduced to the French Pyrenees Alps in northeastern Italy. It occurs in karst landscapes, -which are defined by cave systems, subterranean networks and sinkholes- along the coast of the Adriatic Sea. White olms live in exclusively well-oxygenated low-light freshwater limestone cave systems at a controlled temperature of around 8-11°C (46-51°F) however, they have been known to inhabit near-surface streams during wet seasons and floodings. Although, this is uncommon and they are usually found around 300m (984ft) below the surface. White olms are enigmatic and their population is unknown, though likely in decline.

## Behaviour

The behavioural characteristics of the white olm are seldom-studied due to the species' enigmatic nature however, it is known that they are sociable (or gregarious) animals and males become territorial during aseasonal breeding, though the qualities of a desirable territory are unknown. The exact breeding season is also unknown, though it is known that olm breed every 12 years. The breeding is initiated when a female encroaches upon a males territory. The courtship involves the two putting their snouts against each other's cloaca (a ritual began by the male) and then the male will wave his tail around the snout of the female. The purpose of such a display is hypothesised to be a way of communicating possibly through pheromones. If the female is reciprocal, the male will deposit a spermatophore into her cloaca where she will then store it in a special chamber known as a spermathecae. Though a female will only mate with one male, it is possible that the male is quite promiscuous. 2-3 days after mating, the female white olm will lay fertilised eggs and may continue to lay them for the next 25 days, resulting in an average clutch-size of 35 eggs. The eggs will incubate for around 6 months and hatchlings quickly develop into their adult form, reaching sexual maturity at 14-15 years. A white olm may live up to an average age of 69 years in the wild and may be able to live for 102 years, though this is a hypothetic prediction based on adult survival rates. This long lifespan is likely due to the inactivity of olms and the low environmental-stress they endure.

### Relationship with Humans

The white olm is a symbol of Slovenian natural heritage and has been incredibly popular amongst the Slovenian public and the biology community as a whole. The science of biospeleology -the study of troglobitic life- was partially established in the Postojna cave of Slovenia, due to the interest in the white olm as well as the blind beetles which inhabit the nation's caves. The popularity of the white olm and the Postojna cave have fueled ecotourism in the area, with tours being mostly held around the Proteus Vivarium, a Postojna cave biospeleology base. The olm was also featured on the Slovenian tolar, the nation's currency from late 1991-early 2007. As the white olm is an incredibly respected and unique species in Slovenia, its genus name was used as the namesake for the country's oldest running science magazine; *Proteus*, which began being published in 1993. Illegal pet trading of the olm has also been popular, yet uncommon and due to the protection of the species through much of its range, which greatly limits illegal importation. In pop culture, the name "olm" has been continually associated with mythical dragon-like creatures.

## In Captivity

The Zagreb Zoo, Croatia is the only zoo which houses the olm and has been a very beneficial outlet for olm research in captivity.

## Sources

* IUCN Red List of Threatened Species - https://www.iucnredlist.org/species/18377/89698593
* Olm | Wikipedia - https://en.wikipedia.org/wiki/Olm
* Olm | Animal Diversity Web, University of Michigan Museum of Zoology - https://animaldiversity.org/accounts/Proteus\_anguinus/
* The olm: The blind cave salamander that lives to 100 | National Geographic - https://www.nationalgeographic.com/science/article/the-olm-the-blind-cave-salamander-that-lives-to-100
* 'Human Fish' Salamander breaks lifespan record | NBC News - https://www.nbcnews.com/id/wbna38334490
* Olm | ZOOINSTITUTES - https://zooinstitutes.com/animals/olm-5649/