The reserve of Nosy Mangabe is situated northward the bay of Antongil, at approximately 5km of the coast southward Maroantsetra with an area of 520 ha.
The island shelf is constituted by the granite of the Antongil and is found in a basaltic enclave . The ground is uneven , composed of abrupt slopes and frequent rocky outcrops . One finds many permanent waterways. The pluviometry in the region of Nosy Mangabe is inferior to that recorded at Maroantsetra (4m env.)

The island is covered of ever green humid forest of low altitude. Two centuries ago , a great deforestation would have affected the island. The canopy can reach 35m high on deep grounds. Typical genera are the Canarium, Octea, Raventsara, and Tambourissa. More in altitude, epiphyte ferns are common.

Nosy Mangabe species diversity is reduced , but considering its insularity, the reptiles are particularly abundant. One counts among these the Uroplatus fimbriatus and brookesia peyrierasi. The colubride Pseudoxyrhopus heterurus has been counted three time on the island which is the only known locality.
39 species of birds have been listed on the island among which the "Glaréole" which lays its eggs on the seaside granitic rocks . To be mentionned also the existence of a heron nest sheltering on islets situated southward Nosy Mangabe 7 species of herons (among which the Ardeola idae).
The lemurs are represented by the tawny lemur (Lemur fulvus albifrons) the great Cheirogale (Cheirogalus major), the reddish-brown Microcebe (Microbus rifus) and by two introduced species, the Lemur vari (Varecia variegata) in 1930 and the Aye Aye ( Daubentonia madagascariensis) in 1966.