Though near the main island of Madeira, where the islands can often be seen on the horizon, the geology of the Ilhas Desertas is starkly different. The high, long, and rocky islands of the group are barren of
topsoil, and the only vertebrate
wildlife consists of about sixteen
species of
birds, including eight species of seabirds, and a scarce population of
feral goats,
rabbits, and
rodents, brought from
Portugal by the mariners who first reached the rocky shores. The
Deserta Grande wolf spider and
Madeiran wall lizard also exist in the fragile and
arid ecosystem. There are a number of endemic arthropods and other invertebrates, however, that are more poorly studied. These include two species of
endemic land snail:
Discula lyelliana and
Geomitra grabhami. They had not been observed for over a century, and were presumed extinct by the early 21st century. However, during conservation expeditions conducted between 2012 and 2017, experts from the
Institute for Nature Conservation and Forests rediscovered small populations of the two snail species, each with fewer than 200 individuals. These snails were transferred to zoos in the UK and France and successfully bred in captivity. In 2024, more than 1300 of them were reintroduced to the wild on
Bugio Island. The only inhabitable island, with its own water source, is
Deserta Grande. This water is murky and scarce, and historic attempts to colonise the island failed due to the impracticability of agriculture. A tiny colony of
Mediterranean monk seals inhabits the beaches, and since 1990 the islands have been constituted as a
nature reserve for their protection. In 1998, the colony numbered only eight; now the population is approximately forty seals. The only humans on the islands are the permanent wardens, geologists, occasional boaters, and those who work at the few research stations.
Important Bird Area The Desertas archipelago has been recognised as an
Important Bird Area (IBA) by
BirdLife International because of its
seabird colonies. These include
Fea's and
Bulwer's petrels,
Cory's and
Barolo shearwaters,
band-rumped storm petrels,
common terns and
Caspian gulls. ==See also==