This is a beautiful high-altitude evergreen rainforest, with gigantic trees, lakes with water lilies, and small waterfalls, inhabited by various species of birds, reptiles, and lemurs.

The reserve’s symbol is without a doubt the Indri-Indri, the largest living lemur, whose astounding call echoes in the early morning through the mist-enveloped forest, creating an eerie primordial atmosphere.

The Indri-Indri can be as large as 1 metre.

Its diet consists of around 1.5 kilos of leaves a day, from at least 32 different plant species, which it procures by exploring its territory, extending for about 20 hectares (49.4 acres). For this reason, also, the Indri-Indri cannot survive in captivity.

It is monogamous and stops reproducing if its mate dies. The female is the dominant member of the couple, and can reproduce starting at the age of 6 months, but only once every 2-3 years.

Its only natural enemy is the fosa.

It emits 3 different cries: the territorial cry, which is heard in the morning, serves to let other Indri-Indris know of its presence in its territory, which it will defend at any cost against intrusion by other Indri-Indris, whereas it puts up with the presence of other species of lemurs.

The reserve is also home to 11 other lemur species, including 4 diurnal ones, and the rare nocturnal Aye-Aye; there are also rare birds, chameleons like the large Parsonii and characteristic Nasutus and Brevicornis, other reptiles like geckos, the camouflaging flat-tailed gecko (Uroplatus), and rare frogs like the Mantella (Mantella aurantiaca).

In the immediate vicinity is the Mantadia National Park, still in the organization phase, where it is possible to observe the rare black Indri-Indri.

The dominant ethnic groups are the Bezanozano and the Betsimisaraka.