The small area of Port-Cros is not suitable for large animals. However, for some species the island is the ultimate refuge from predators. For migratory birds, It is at the crossroads of seasonal movements between Europe and Africa, and is a favorite stopover.
The avifauna of the island of Pros Cros has some rare breeding species such as the yellow-legged gull (whose population is no longer endangered), the booted eagle (a rare migratory bird), the peregrine falcon , Cory's shearwater and the puffin yelkouan (Puffin de Méditerranée). Many migratory birds stay on the island during the spring, and autumn.
In the spring, the island also hosts many migratory birds such as the black kite, the European honey buzzard but also different types of sparrows such as the bee-eater and the hoopoe. Out of the 177 species of birds observed, 26 nest here, including the common nightingale, the chiffchaff, the chaffinch, three species of tits, and four different species of warblers.
Among the birds of prey, it is more common to observe the hawk or the kestrel than the peregrine falcon. As for the rare Eleonora's falcon, it was recently seen on the islands. At night, it is common to hear the scops owl calling.
Among the sea birds, the numbers of the yellow-legged gull have become stable. In the summer, it is common to see Cory's shearwater, and some young cormorants from Corsica. In the winter Northern gannets can be seen diving and puffin yelkouans flying in loops.
The wildlife includes some particular species such as the Tyrrhenian painted frog (an amphibian) and the European phyllodactyle (a small gecko endemic to Port-Cros, Corsica and Sardinia).
There are also large and varied populations of invertebrates and bats .
Out of the eleven species of mammals on the island, bats are the most numerous (7 species); the others were unintentionally introduced by man over the centuries (black rats, feral cats, field mice, rabbits).
The ladder snake eats rats, helping to limit their proliferation. Animals common to the Mediterranean area are the Montpellier snake, (measuring up to 2 metres, the largest French reptile) along with the gecko, mainly active at night (they are of part the reptile family but have a vertical pupil and prehensile suckers under the fingers).
Also common to Corsica and Sardinia, the Tyrrhenian painted frog is a very rare species, originally part of the ancient Ligurian proto-continent 6 million years ago.