Not many of the visitors to the caves know that there are multiple types of underground animals that have their habitat inside the caves. This area has been gradually populated by different animals since the beginning of its formation. They have adapted to living in these special conditions such as constant darkness, high average air humidity and a relatively low and constant temperature. The animals change their appearance during their long-term adjustment to a new living environment.
By living in constant darkness, they lose their eyesight, but further develop sense of smell in order to find scarce food sources necessary for survival. Extended antennas serve as a sense of touch that, in combination with elongated legs, help navigate their movements through the darkness. The body color which helped protect them from the harmful influence of the Sun and as a disguise from predators has lost its significance in the underground. Most animals have completely or partially lost pigment, so they are mostly white or brown. The animals that live underground have extremely scarce food resources so only smaller invertebrates could have adapted to such conditions. Those are mostly small insects, spiders, pseudoscorpions, centipedes, snails, crabs and others.
Besides invertebrates, bats also use caves as their homes or occasional shelters. Greater horseshoe bat (Rhinolophus ferrumequinum) has been found in Cerovac caves. It is listed in the Red Book of Mammals of Croatia under the category of potentially endangered species.