Few animals are adapted for a life spent entirely in caves, but there are two known in the Yorkshire Dales.
The minute, blind crustacean Anthrobathynella stammeri has been recorded amidst gravels and silts in the stream bed and in pools in White Scar and Great Douk Caves, Ingleton. It also occurs in those sections of the River Skirfare that flow beneath the usual river bed where surface waters and groundwater mix.
A small, flattish (3-4 mm) water beetle, Hydroporus ferrugineus may be found deep underground and in some parts of the UK it has been pumped up in well water. Oddly, although it is apparently flightless (unlike most water beetles), it has been found on islands like Anglesey and Mull and at the top of some mountains. Most often in the Dales it has been recorded from the mouths of springs after heavy rain, most commonly on moorland on sandstone rather than limestone.
Other animals find shelter in caves. The Cave Spider, Meta menardi tends to live at the entrances to caves, where some light still penetrates and insect prey may fly in, but the 2 – 3 mm money spider Porhomma convexum has been found in the darkest depths. Despite the occurrence of these predators, large numbers of particular moths – such as Herald Moth, Tissue Moth and Winter Moth – hibernate in caves.
Bats also hibernate in cave systems, but they also congregate around some of the cave entrances in autumn to mate. Such ‘swarming sites’ are very important to populations of species like Brandt’s Bat, Daubenton’s Bat, Natterer’s Bat, Brown Long-eared Bat and Whiskered Bat. The complex of caves in the Ease Gill/Leck Fell area of the National Park attracts thousands of bats to swarm.
Animals can end up in caves by accident rather than choice. Brown Trout or Bullhead fish may be washed into caves and can be found in pools within, as can freshwater shrimps. The shrimps and the Trout may lose their usual pigmentation if they spend any length of time in the caves, although the Bullheads, seemingly, do not.