Hidden from the eyes, in the eternal darkness of underground fissures and tunnels, true cave specialists roam. The most famous among them is the narrow-necked blind cave beetle, the first described cave beetle in the world.
On the shoals by the Rak's springs, tiny but not sandy beaches are created... They are formed with shells of underground snails. Among them there are two native species which cannot be found elsewhere in the world.
During the day, dragonflies are buzzing by the Rak bank, May-, stone- and caddisflies are completing their larva cycle in the water and rising beneath tree crowns on their gentle wings, and water striders are rushing along the still surface by the shore.
The abundance of water invertebrates is a feast for fish. Chubs are lazily circling in pools, here and there pikes are lurking in the ambush, brown trout is hiding behind rapids, and burbot is waiting for the night to fall.
In the meantime, scarce fritillaries, Jersey tigers and other butterflies are searching for sweet nectar and mates at the edge of the forest, long-horned beetles are jostling on fir stumps in the safety of the forest, and harvestmen, cave crickets and other surface species, common visitors to the underground entries, are lingering by sunken valleys and cave entrances.