The Monte Loayza Provincial Nature Reserve occupies a coastal strip and a marine area south of the San Jorge Gulf and constitutes one of the most valuable bird and marine mammal colonies on the Patagonian coast, both for the diversity of species and the size of the populations it shelters. It is home to large breeding colonies of several species of birds and marine mammals, and is also frequented by elephant seals, Antarctic pigeons and giant petrels. Particularly noteworthy are: (a) the largest breeding colony of fur seals in the province of Santa Cruz, which is also one of the most important in Argentina; (b) breeding colonies of imperial cormorants, black-necked cormorants and gray cormorants. The area is home to the northernmost colony of the gray cormorant, which has a restricted distribution in Argentina; (c) breeding colonies of kittiwakes and southern gulls; and (d) nesting sites of at least two species of oystercatchers and the white-headed steamer duck.

Together with the Cañadón del Duraznillo Associated Buffer Reserve, with integrated management since 2010,  they represent a management  unit.