Paul Kammerer reported that female olm gave birth to live young in water at or below 13 °C (55 °F) and laid eggs at higher, but rigorous observations have not confirmed that...
The average is 35 eggs and the adult female typically breeds every 12.5 years...
Controlled experiments have shown that an olm can survive up to 10 years without food....
Olms are gregarious, and usually aggregate either under stones or in fissures....
The male can start courtship even without the presence of a female. He chases other males away from the chosen area, and may then secrete a female-attracting pheromone. When the female approaches, he starts to circle around her and fan her with his tail. Then he starts to touch the female's body with his snout, and the female touches his cloaca with her snout. At that point, he starts to move forward with a twitching motion, and the female follows. He then deposits the spermatophore, and the animals keep moving forward until the female hits it with her cloaca, after which she stops and stands still....
Longevity is estimated at up to 58 years. A study published in Biology Letters estimated that they have a maximum lifespan of over 100 years and that the lifespan of an average adult is around 68.5 years. When compared to the longevity and body mass of other amphibians, olms are outliers, living longer than would be predicted from their size....