As in other arid regions, the mammals of the Pilbara are masters of endurance – often persisting in low numbers when resources are low and rapidly recolonising habitats when conditions improve. Most do not need to drink water but obtain enough from their food. Some store fat in their tails. Many small bats and marsupials can enter daily torpor, dropping their metabolic rate by 90% or more compared to when they are active. In this way, they can survive on little or no food for days to months and greatly reduce their exposure to predators.
For an arid region, the Pilbara once had a rich mammal fauna. Before European colonisation there were at least 60 species, a number exceeded in Australia’s arid bioregions only in the Carnarvon bioregion. Six species are unique to the Pilbara or almost so (extending slightly into adjacent regions) – 2 undescribed planigales (tiny carnivorous marsupials), western pebble-mound mouse, little red kaluta, Pilbara ningaui, and Rothschild’s rock wallaby.
Despite the toughness of arid-zone mammals, many have been unable to endure the new predators introduced in the 1800s – feral cats and foxes. The Pilbara has lost 20% of its known mammal fauna (12 species), almost all in the preferred weight range of prey for cats and foxes (35– 5500 grams). Most survivors vulnerable to cat or fox predation have lost much of their former range, including 2 species confined to coastal islands and 1 to the coast. Of the 48 surviving mammal species, 4 are listed as threatened (at state and national levels) and 7 are listed as priority species by the Western Australian Government. The extinctions and declines mean that the Pilbara mammal fauna is now dominated by small species (weighing less than 35 grams). It also means that important ecological functions have been compromised, such as the turnover of soil.
Despite the losses, the Pilbara still has 60 mammal species, due to the addition of 12 introduced mammals, including cats, foxes, pigs and donkeys.