Ankarana Special Reserve: Mapping the Karst Landscape and Jurassic Limestone of Northern Madagascar

Ankarana was formally established as a protected area on 20 February 1956, giving it one of the longer continuous conservation histories in northern Madagascar. Its rugged terrain meant that legal protection reinforced, rather than created, the plateau’s isolation from large-scale exploitation, and the reserve has remained under the care of Madagascar National Parks as an IUCN Category IV habitat and species management area.

Modern scientific and speleological interest in the massif expanded in the 1960s, when Jean Duflos, later known as Jean Radofilao, began an extensive programme of cave exploration across the plateau, much of it alone or in collaboration with visiting speleologists. By the time his work was more broadly published, around 100 kilometres of cave passages had been mapped within the Ankarana Massif, revealing what are recognised as the longest cave systems in Madagascar, and likely in Africa as a whole.

A second important chapter opened in the 1980s, when a series of scientific expeditions began systematically documenting the reserve’s animals and plants. Researchers published bird lists, descriptions of mixed-species foraging behaviour, and an array of new or previously unrecorded invertebrate species from the caves. These expeditions also uncovered sub-fossil remains of large extinct lemurs, including Babakotia radofilai, species of Mesopropithecus and Palaeopropithecus, Megaladapis, Archaeolemur, and the indri, transforming Ankarana into a key site for understanding Madagascar’s vanished megafauna. The explorer-scientist tradition that began with Duflos and continued through these expeditions is the foundation on which Ankarana’s modern identity as a destination for both adventure travel and serious field research rests.

The defining feature of Ankarana is its plateau of middle Jurassic limestone, around 150 million years old, which has been shaped over time into a dense, sharply etched karst landscape. The plateau slopes gently to the east, but to the west it ends in the dramatic Wall of Ankarana, a sheer cliff that runs roughly 25 kilometres north to south and rises up to about 280 metres, separating the massif from the surrounding lowlands.

Towards the south, the continuous cliff face breaks up into a scatter of isolated limestone spires known as tower karst, while the interior of the plateau is crossed by seismic activity and long-continued rainfall into a network of deep gorges and ribbons of flowstone. In areas where the softer upper layers of limestone have been stripped away, the harder base rock has been etched into channels and ridges known locally as tsingy, a Malagasy word meaning ‘where one cannot walk barefoot’. Scattered basalt boulders and old basalt flows through the canyons add a darker, volcanic accent to what is otherwise a pale limestone world.

Below the surface, the same carbonate geology has produced an exceptional underground landscape of caves, chambers, and subterranean rivers. Roughly 100 kilometres of cave passages have been mapped, including long horizontal systems such as La Grotte d'Andrafiabe, which alone contains more than eight kilometres of mapped horizontal galleries, making the massif an internationally significant site for karst and speleological study.

Ankarana sits within the humid tropical climate of northern Madagascar, with rainfall close to 2,000 millimetres per year, and its vegetation reflects this combination of heat, moisture, and thin, sharply drained soils. The plateau is only partially vegetated, with dense patches of forest clinging to deeper soils and moister areas, while the bare tsingy ridges, cliff faces, and exposed rock surfaces remain largely unvegetated. Where soil accumulates in sheltered pockets, plant cover can become dense enough to make movement difficult, and it is partly this density, together with the rugged relief, that has protected the massif from outside pressure.

The ecological pattern of the reserve is shaped by the underlying geology. Drainage dissolves into karst systems rather than running off in surface rivers, the microclimate varies sharply between exposed rock and shaded gorges, and habitat for ground-dwelling species differs strongly from that of the canopy. These contrasts support a wide range of niches within a relatively small area and help explain the unusually high species density for certain groups, particularly lemurs and forest-interior birds.

In addition to its living vegetation, Ankarana preserves an extraordinary natural archive in its caves and sinkholes, where sub-fossil deposits have preserved the remains of extinct lemurs that were considerably larger than any surviving Malagasy primates. These deposits have made the reserve a key reference point for understanding how Madagascar’s unique primate fauna has changed over time, blending living biodiversity with a deep palaeontological record in a single landscape.

Ankarana is most famous for its lemurs, which include crowned lemurs and Sanford’s brown lemurs as two of the reserve’s signature species. Field records also document the northern sportive lemur, brown mouse lemur, fat-tailed dwarf lemur, fork-marked lemur, eastern woolly lemur, Perrier’s sifaka, aye-aye, and the western lesser bamboo lemur, giving the plateau an unusually complete cross-section of Madagascar’s nocturnal and diurnal primate guilds within a relatively compact area.

Birds are another highlight. Surveys undertaken as part of the 1986 expedition recorded 65 species from 32 families, representing almost a third of Madagascar’s breeding bird species. Many of these small insect-eating songbirds, including paradise flycatchers, common jery, greenbuls, the Malagasy bulbul, sunbirds, and several vangas, forage together in mixed flocks in which each species concentrates on a different part of the tree, from trunk to branches to slender boughs and undersides of leaves. This division of foraging roles, which improves both feeding efficiency and predator detection, is a striking behavioural feature of the Ankarana bird community.

The reserve’s wildlife significance extends beyond living species into its caves and sinkholes, which have yielded sub-fossil remains of the greater bamboo lemur, indri, sloth lemur (Babakotia radofilai, named after the explorer Jean Radofilao), Mesopropithecus, Palaeopropithecus, Megaladapis, and Archaeolemur. These finds have transformed Ankarana into a key site for understanding the lost megafauna of Madagascar and have given the reserve a presence in both modern conservation and the broader study of primate evolution.

Ankarana’s conservation importance rests on the unusual combination of geological inaccessibility and biological richness concentrated in a relatively small area. The tsingy ridges, the Wall of Ankarana, and the dense plateau vegetation have together created a physical barrier to large-scale logging, agriculture, and other forms of exploitation, allowing the reserve to retain much of its original character more than half a century after it was first protected.

Formally designated in 1956 and managed today by Madagascar National Parks as an IUCN Category IV habitat and species management area, Ankarana plays an important role for several threatened and endemic species. It supports significant populations of crowned lemurs and Sanford’s brown lemurs, along with a wider lemur community that includes species of conservation concern such as the aye-aye, Perrier’s sifaka, and the northern sportive lemur. Its bird and invertebrate fauna also include species first characterised through expeditions to the massif.

Beyond its living biodiversity, the reserve’s cave systems have preserved sub-fossil deposits of extinct lemurs, giving Ankarana scientific and conservation value as a natural archive of Madagascar’s evolutionary past. Protecting these deposits, together with the fragile surface ecosystems above, is a continuing challenge for park management, particularly given the pressures affecting protected areas across Madagascar, but the reserve’s physical setting and long history of formal protection make it one of the more resilient strongholds for the country’s distinctive wildlife.

Ankarana sits in the Diana Region of northern Madagascar, and the surrounding landscape is shaped by the same plateau that defines the reserve. The Malagasy name tsingy, used for the jagged limestone formations on the plateau, is itself a piece of local culture, a short, practical warning that captures the difficulty of walking across the sharp rock in a single word and reflects generations of local knowledge about the terrain.

The reserve is also linked to the broader story of scientific exploration in Madagascar. The French explorer Jean Duflos, who later took the Malagasy name Jean Radofilao, spent much of the 1960s and later years mapping its caves and underground rivers, and one of the extinct lemurs later found in the reserve, Babakotia radofilai, was named in his honour. The intersection of local place names, Malagasy identity, and international scientific work gives Ankarana a layered cultural and historical presence that complements its natural significance.

Among Ankarana’s most distinctive features are the tsingy limestone ridges and the Wall of Ankarana, a 25-kilometre-long cliff rising up to about 280 metres that forms the western edge of the massif. Together these define the reserve’s visual identity and make its landscape instantly recognisable within Madagascar.

Equally important are the underground systems: around 100 kilometres of mapped cave passages, including the horizontal galleries of La Grotte d'Andrafiabe, rank Ankarana as the holder of Madagascar’s, and arguably Africa’s, longest cave network. Above ground, the reserve supports strong populations of crowned lemurs and Sanford’s brown lemurs, a remarkable 65-species bird community, and a unique set of sub-fossil sites that have preserved extinct giant lemurs, giving Ankarana a rare blend of landscape, wildlife, and palaeontological significance.

Ankarana lies in the wet tropical north of Madagascar, where the year is shaped more by the alternation between wetter and drier periods than by sharply contrasting seasons. Visitors tend to find conditions most rewarding during the drier months, when the tsingy ridges and cave entrances are more accessible, forest paths are firmer underfoot, and bird and lemur activity around fruiting trees is easier to observe.

In the wetter part of the year, the same rainfall that creates the karst landscape also makes underground rivers swell and can make some tracks slippery or difficult, though the vegetation is at its lushest. Travellers interested in the caves should generally expect that water levels underground will be higher during the rains and lower during the dry season, while those focused on seeing lemurs and birds will find that fruiting peaks shape seasonal visibility more than any single calendar window.