The Comoros archipelago comprises four main islands aligned along a northwest–southeast axis at the northern end of the Mozambique Channel, between Mozambique and Madagascar. Although still widely known by their French names, the islands are officially referred to by their Swahili names by the Comorian government: Grande Comore (Njazidja), Mohéli (Mwali), Anjouan (Nzwani), and Mayotte (Mahoré). The islands lie relatively far apart—Grande Comore is about 200 kilometers (124 miles) from Mayotte, 40 kilometers (25 miles) from Mohéli, and 80 kilometers (50 miles) from Anjouan—and the scarcity of good harbors makes transportation and communication challenging. The islands enjoy abundant sunshine throughout the year.
Together the islands cover a total land area of 2,236 square kilometers (863 square miles), including Mayotte, and claim territorial waters of 320 square kilometers (124 square miles). They sit on the Somali Plate. Mount Karthala (2,361 m / 7,746 ft) on Grande Comore is an active volcano; between 17 and 19 April 2005 it erupted ash and gas, forcing as many as 10,000 people to evacuate.
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Grande Comore (Njazidja)
The largest island, Grande Comore measures 67 kilometers (42 miles) long and 27 kilometers (17 miles) wide, with an area of 1,146 square kilometers (442 square miles). It is the youngest of the four islands and is entirely volcanic in origin. Two volcanoes dominate its landscape: the extinct and heavily eroded La Grille in the north (1,000 m / 3,281 ft) and Mount Karthala in the south (2,361 m / 7,746 ft), which last erupted in 1977. A plateau averaging 600 to 700 meters (1,969 to 2,297 ft) in elevation links the two peaks. Because the island is geologically young, its thin, rocky soils hold little water; heavy rainfall must therefore be collected in catchment tanks. The coastline lacks coral reefs and offers no good natural harbor. Significant remnants of the once-extensive Comorian rain forests still cling to the slopes of Mount Karthala. The national capital has been located at Moroni since 1962.
Anjouan (Nzwani)
Triangular in shape and 40 kilometers (25 miles) from apex to base, Anjouan covers 424 square kilometers (164 square miles). Three mountain chains—Sima, Nioumakele, and Jimilime—radiate from the central peak of Mtingui (1,575 m / 5,167 ft), giving the island its distinctive form. Older than Grande Comore, Anjouan possesses deeper soils, yet overcultivation has produced serious erosion. A coral reef lies close to the shore. The island’s capital and principal port is Mutsamudu.
Mohéli (Mwali)
Mohéli, the smallest of the four islands, is 30 kilometers (19 miles) long and 12 kilometers (7.5 miles) wide, with an area of 290 square kilometers (112 square miles). A central mountain chain rises to 860 meters (2,822 ft). Like Grande Comore, it retains stands of rain forest. Its capital is Fomboni.
Mayotte (Mahoré)
Geologically the oldest island, Mayotte measures 39 kilometers (24 miles) long and 22 kilometers (14 miles) wide, with an area of 375 square kilometers (145 square miles). Its highest elevations reach only 500 to 600 meters (1,640 to 1,969 ft). Greater weathering of the volcanic rock has produced relatively rich soils in places. A well-developed coral reef encircles much of the island, sheltering ships and providing fish habitat. Dzaoudzi, capital of the Comoros until 1962 and now Mayotte’s administrative center, stands on a rocky outcrop off the eastern shore of the main island and is linked by a causeway to Île Pamanzi (10 km² / 4 square miles), the largest of several nearby islets. Similar islets also fringe the coasts of Grande Comore, Anjouan, and Mohéli.
Wildlife
The African Coelacanth (Latimeria chalumnae) is a rare fish with limb-like fins and a cartilaginous skeleton. Long thought extinct, a living specimen was caught off southern Africa in 1938; additional individuals have since been found near the Comoros, which host one of the largest known populations. These nocturnal fish spend daylight hours resting in deep volcanic caves and canyons (typically 150–300 meters / 490–980 feet deep, occasionally to 700 meters / 2,300 feet), emerging at night to drift-hunt for fish, squid, and other prey along steep rocky slopes. They can grow to nearly 2 meters (6.6 feet) long, live for decades, and have a slow metabolism and multi-year gestation. The species is Critically Endangered, with threats including accidental capture in fishing nets.
Several mammals are endemic or unique to the islands. Livingstone’s Fruit Bat (Pteropus livingstonii), also known as the Comoro Flying Fox, is one of the world’s largest bats, with a jet-black coat and a wingspan of nearly two meters (6.6 feet). Discovered by David Livingstone in 1863 when it was still plentiful, it is now restricted to montane forest on Anjouan and Mohéli (above roughly 200–500 meters / 660–1,640 feet). Recent surveys estimate a global population of 1,200–1,500 individuals, and the species was downlisted from Critically Endangered to Endangered by the IUCN in 2025 thanks to improved monitoring showing population stability. Habitat loss from deforestation remains the primary threat; local conservation groups protect key roost sites through community agreements, and captive breeding programs exist in Europe. Another endemic bat is the smaller Comoro Rousette (Rousettus obliviosus).
A hybrid of the Common Brown Lemur (Eulemur fulvus), originally from Madagascar, was introduced by humans prior to European colonization and is found on Mayotte (sometimes treated as the subspecies Eulemur fulvus mayottensis). The Mongoose Lemur (Eulemur mongoz), also introduced from Madagascar, occurs on Mohéli and Anjouan. These diurnal primates feed primarily on fruit (especially mango and jackfruit), leaves, and flowers; they face pressures from habitat loss and occasional capture as pets, though they are not typically hunted for food in the Comoros.
The archipelago supports high bird endemism, with about 21 species unique to the islands (17 restricted to the Union of the Comoros). Each of the three main islands of the Union has its own scops-owl: the Karthala Scops-Owl (Otus pauliani) on Grande Comore (confined to the forests and heath of Mount Karthala), the Anjouan Scops-Owl (Otus capnodes) on Anjouan, and the Mohéli Scops-Owl (Otus moheliensis) on Mohéli—all Endangered due to habitat fragmentation. Other notable endemics include Humblot’s Flycatcher (Humblotia flavirostris), the sole member of its genus and restricted to Grande Comore forests; the Comoro Blue Pigeon (Alectroenas sganzini); the Comoro Olive Pigeon (Columba pollenii); the Comoro Green-Pigeon (Treron griveaudi); various white-eyes, brush-warblers, bulbuls, and the Comoro Drongo (Dicrurus fuscipennis). Many of these forest-dependent species are threatened by ongoing deforestation.
Reptile diversity includes several endemics, such as day geckos (Phelsuma species), the Comoro Flapnose Chameleon (Furcifer cephalolepis), snake-eyed skinks, and other lizards adapted to forest and coastal habitats. Marine life is rich: green and hawksbill sea turtles nest on the beaches (especially Mohéli), dugongs occur in coastal waters, and coral reefs support diverse fish communities. Overall, the Comoros’ isolation has produced a high proportion of endemic species relative to its small size, but rapid forest loss and human pressure place many of them at risk.
Environment and conservation
Responding in part to international pressure, Comorians became more environmentally aware in the 1990s. Efforts now focus both on protecting rare fauna and on reversing environmental degradation, especially on densely populated Anjouan. To reduce tree-cutting for fuel, kerosene is subsidized, and programs seek to restore forest cover lost to Ylang-Ylang (Cananga odorata) distillation for perfume. The Community Development Support Fund, backed by the International Development Association (a World Bank affiliate) and the Comorian government, works to improve water supplies across the islands.
Climate
The climate is tropical marine, with two seasons: a hot, humid period from November to April driven by the northeastern monsoon, and a cooler, drier season for the remainder of the year. Average monthly coastal temperatures range from 23 °C to 28 °C (73.4 to 82.4 °F). Although annual rainfall averages 2,000 millimeters (79 inches), water remains scarce in many areas. Mohéli and Mayotte have streams and other natural water sources, but the mountainous terrain of Grande Comore and Anjouan retains water poorly and is nearly devoid of permanent running water. Cyclones during the wet season can cause extensive damage, particularly along the coasts; on average, houses, farms, and harbor facilities are devastated at least twice each decade.
Extreme points
(Excluding the French-administered island of Mayotte, which is claimed by the Comorian government)
- Northernmost point: unnamed headland northwest of Bangoua Kouni, Grande Comore
- Easternmost point: unnamed peninsula east of Domoni, Anjouan
- Southernmost point: unnamed headland on Île Canzouni, Mohéli
- Westernmost point: unnamed headland west of Iconi, Grande Comore
