The Nullarbor Plain is a low plateau of Tertiary limestone in southern Australia. Its caves may be classified as deep or shallow. They occur in the inland open shrub steppe zone, and the coastal mingled arid scrub and semi-arid mallee zone. Comparison is made between surface, doline and cave climate in both regions, and the significance of the special climatic conditions on the fauna is discussed. Although caves appear extremely dry, relative humidity is fairly high. Animal burrows have a microclimate intermediate between caves and surface. Plants on the surface are xerophytes, and many are halophytes; but in the dolines they are less salt-tolerant and require moister, more sheltered conditions. Many vertebrates use the caves as temporary shelters, while others may be trapped in them accidentally. Nineteen species are recorded–eight mammals, eight birds and three reptiles.

Arthropods are the principal inhabitants of the caves. Ninety-five species belonging to 17 orders and 58 families are recorded from 47 caves, and their distribution is given. Of these 25 % are accidentals, 17 % trogloxenes, 52 % troglophiles and 6 % troglobites. About 80 % are identified to genus or species. Within the caves four biotopes are examined–the Parietal Association, the Guano Association, the Dark Zone and the Liquid Medium. The species are grouped into several associations within the first three biotopes–on walls, on floor, under stones, around carcases, amongst guano and decaying vegetation. No macroscopic species have been found in the underground lakes. Only one arthropod species is definitely associated with deep as opposed to shallow caves. About 69% of the species are predators or saprophages; the rest are coprophages, necrophages or ectoparasites. Saprophages or coprop-hages comprise the greatest number of individuals in the population. Food preferences are listed for a number of arthropods, and a generalized food web has been constructed. Some species travel considerable distances throughout the caves, and a number of Dark Zone species are recorded on the entrance talus slope, in the dolines, or on the surface. About 59 % of the species are known only from a single cave, but 29 % are widely distributed across the plain. Cave “breathing”, the cool, humid night climate, strong winds, occasional heavy rain and numerous animal burrows all contribute to the distribution of cave-frequenting species across the plain. Subterranean migration may also occur. The cave arthropods may be divided into two groups, one much older geologically than the other. It is suggested that specific climatic conditions have been required for colonization of the caves, and these are considered in relation to current information on the Quaternary climate of the Nullarbor. Much recent colonization has been by species from eastern Australia.