Indonesia is taken into account the country with essentially the most mammal species on this planet. According to the Mammal Diversity Database managed by the American Society of Mammalogists (December 2025), Indonesia has 777 documented mammal species, barely greater than Brazil with 776 species and China with 710 species.
Overall, Indonesia’s mammal diversity includes 793 extant species and 4 extinct species, distributed in 17 orders, 58 families and 241 genera. This list doesn’t include domesticated species or species with a really wide global range, but their extinction status is calculated based on records from the last 500 years.
So what makes Indonesia home to such a rare variety of mammals?
Archipelagic nation: isolation that generates latest species
A key factor is Indonesia’s structure as an archipelagic country. Consisting of over 17,000 islands, Indonesia’s landscapes create hundreds of distinct habitats. Geographic isolation over long evolutionary periods allowed mammal populations to evolve independently, resulting in the emergence of recent species.
The theory of island biogeography explains that enormous islands positioned near major land masses have high rates of species colonization, while smaller and more isolated islands have higher rates of natural extinction but additionally show high levels of endemism. This pattern is clearly visible in Indonesia.
Western regions resembling Sumatra, Java, Bali and Kalimantan have high species richness because they were once connected to mainland Asia. In contrast, the more isolated eastern regions are home to many unique species found nowhere else on this planet.
However, island isolation also makes ecosystems more vulnerable. Data shows that 93 percent of bird species declared extinct since 1600 are native to the islands. This pattern could be very vital for understanding the threats Indonesia’s wildlife faces.
A natural transition zone
The second key factor is geological history. Indonesia lies on the confluence of three major tectonic plates: the Eurasian, the Philippine and the Australian. This unique location divides Indonesia into three major biogeographic regions: Sundaland, Wallacea and Sahul.
Western regions resembling Sumatra, Java, Bali and Kalimantan lie on the Eurasian plate and were once connected to mainland Asia. This connectivity enabled large-scale migration of Asian mammals into the region.
However, Papua and West Papua lie on the Sahul shelf, which has strong geological connections with Australia. When sea levels fell about 19 million years ago, the realm joined Australia, allowing species to maneuver freely between the 2 continents.
Between these zones lies Wallacea, which incorporates Sulawesi, Maluku and Nusa Tenggara. This region serves as a transition zone, containing a combination of Asian and Australian elements, in addition to a lot of unique species.
Sulawesi provides the clearest example. The island is a habitat of endemic small mammals, especially rodents (Muridae and Sciuridae) and shrews (Soricidae). Many species within the region are classified as threatened, have data missing or have only recently been described, meaning scientific research stays limited.
Biodiversity in danger
Indonesia’s land area is simply about 1–1.3% of the world’s total land area. Yet it’s home to roughly 12 percent of the world’s mammal species, 10 percent of plant species and 17 percent of bird species.
Indonesia also incorporates the third largest area of tropical forest on this planet, after the Amazon and the Congo Basin. These forests provide critical habitat for orangutans, Sumatran tigers, Javan rhinos and lots of lesser-known species.
This concentration of biodiversity is accompanied by intense pressure. Indonesia leads the world within the variety of endemic mammal species, and at the identical time has the biggest variety of endangered mammals.
FAO data shows a net forest loss of roughly 684,000 hectares per yr between 2010 and 2015, mainly on account of agricultural expansion, plantation development, and timber and mineral extraction. Land clearing through burning, especially for oil palm plantations, has accelerated habitat degradation.
Indonesia also faces additional risk aspects in the shape of volcanic activity and earthquakes. The country has 76 energetic volcanoes, which is the biggest number on this planet. Disasters resembling volcanic eruptions, tsunamis and landslides have a direct impact on ecosystems and wildlife populations.
At the identical time, the Ministry of the Environment estimates that greater than half of the species present in Indonesia haven’t yet been scientifically documented. This suggests that the variety of 777 mammal species may not fully reflect the country’s true biological potential.
Indonesia’s high mammal numbers aren’t the results of a single factor, but moderately a mixture of its archipelagic nature, geological history, biogeographic transition zones and extensive tropical forests. The data confirms that Indonesia is certainly one of the world’s major centers of mammal biodiversity, facing equally serious conservation challenges.
Source:
- https://www.mammaldiversity.org/country/ID/
- https://www.ifaw.org/projects/protecting-indonesias-endangered-wildlife
- https://www.ran.org/indonesia_s_rainforests_biodiversity_and_endangered_species/
- https://www.cambridge.org/core/journals/oryx/article/conservation-status-and-priorities-for-sulawesis-unique-small-mammal-fauna/A62EBE457E255E9E8AE3B4F0F4D8D667
