Olm

Proteus anguinus

Amphibian

Transcript:

Today on Animal Fact Files we’re discussing olms. These animals are also known as blind cave salamanders which is appropriate because their eyes are so tiny they’re covered by skin. Olms are fully aquatic amphibians who live their entire lives in caves. Olms can be found in caves in central and southern Europe up to 1,000 feet (300m) underground. They specifically live in karsts which are places where rocks like limestone have been eroded by water thus creating the difficult to reach caves in which the olms live.

The temperature in this habitat is consistent and olms tend to remain within a range of 46 and 52 degrees (8 to 11 degrees C), though those living closer to the surface may tolerate up to 57 degrees (14 degrees C). Olms may appear light in color. These olms have bright red external gills and when exposed to light their skin darkens, meaning they aren’t albinistic as previously believed. There are also darker variants who were once believed to be a subspecies, though this is now contested. These darker variants are more rare, have shorter heads, and live closer to the surface.

Something fascinating about olms is that their front feet have three toes while their back feet only have two! Also, the paler individuals can be see-through on their undersides, much like glass frogs, which makes determining their sex easy for scientists studying them! While olms don’t have any known predators, other threats to olms include habitat loss and pollution which has contributed to the loss of known populations.

The paler individuals aren’t known to reach more than 10 inches (25cm) while the darker individuals may max out at 16 inches (40cm). While it tends to be the rule that larger animals need more food to fuel their large bodies, that’s not always the case with olms. Olms have a low metabolic rate and efficient fat storage in their tails and livers which allows them to remain, sometimes motionless, for years on end without eating. When they do eat, olms mostly consume insects and insect larvae. Though their eyes can detect light, olms have lost their sense of vision. Instead, they depend on other senses in order to find a meal. They can feel movements in the water and have big snoots for picking up chemical cues. This may also be how omls find each other for breeding.

Omls are gregarious meaning they hang out in groups in crevices and under rocks. During breeding times, however, males will become aggressive towards each other and establish breeding territories. Here they’ll wait for females to come to them for mating. Males may mate with several females while females tend to stick to just one male. A male wiggles his tail towards the female, and guides her over a spermatophore which she’ll quickly pick up and take in through her cloaca where her eggs will be fertilized internally.

The female will leave and develop her own egg laying spot where she’ll begin laying eggs about 2-3 days after mating. She’ll lay eggs for about a month producing upwards of 70 eggs laid under rocks and in crevices. She’ll guard the eggs as they incubate which may take anywhere from 90 to 180 days depending on the surrounding temperature.

The babies hatch looking like smaller versions of adults because, like axolotls, olms are neotenous, meaning they retain their juvenile characteristics throughout their lifetime. It’ll be 15 years before the young are ready to reproduce and this cycle will only occur every 12 years. It’s not exactly known how long olms can live, but it’s estimated they may live longer than 100 years which would make them the longest living known amphibians alive today!

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