List of threatened, endangered and extinct species in the Mariana Islands

The following is a list of species (or subspecies) in the Mariana Islands, defined by the International Union for Conservation of Nature (IUCN) Red List or by the U.S. Fish & Wildlife Service (USFWS), as being extinct, critically endangered, endangered, threatened, vulnerable, conservation dependent, or near threatened. This article addresses species found in the geopolitical states of Guam and the Commonwealth of the Northern Mariana Islands (CNMI).
As of 2024, there were 32 species or subspecies in the Mariana Islands listed by the U.S. Fish & Wildlife Service as endangered or threatened. USFWS has cited threats to species from habitat loss and degradation; military activities; urbanization; recreational vehicles; nonnative animals such as feral ungulates (wild boar and sambar deer), water buffalo, rats, brown tree snakes, slugs, flatworms, ants, and wasps; nonnative plants; fires; typhoons; water extraction; and future climate change.
As of 2024, the USFWS and IUCN together listed 9 species or subspecies endemic to the Mariana Islands that have gone extinct: the little Mariana fruit bat (Pteropus tokudae); 5 birds (Guam flycatcher (Myiagra freycineti), bridled white-eye (Zosterops conspicillatus conspicillatus), Pagan reed-warbler (Acrocephalus yamashinae), Aguijan reed-warbler (Acrocephalus nijoi), the Mariana mallard (Anas oustaleti); and 3 snails (Partula desolata, Partula langfordi, Mount Alifana partula (Partula salifana)). Archaeological evidence has revealed another snail from Guam, the Partula desolata, to be extinct. Four undescribed and extinct bird species were excavated from Rota. Additionally, the Guam kingfisher (Todiramphus cinnamominus) is listed by the IUCN as extinct in the wild.
Significant loses of bird species have likely occurred in the Mariana Islands in the past few millennia. A 1990 excavation of a late Holocene archeological site on Rota revealed the presence of 21 bird species, 12 of which have since become extinct or extirpated from Rota. Four of the species were not yet described and extinct: a small probably-flightless duck (Anatidae species), a giant ground-dove (Gallicolumba species), a large parrot (Psittacidae species), and a large parrotfinch (Erythrura).
The endemic birds of Guam, the southernmost Mariana island, were severely affected by the introduction of the brown tree snake after World War II. It has been reported that 11 of Guam's 14 terrestrial birds have become extinct or extirpated from Guam. A new tally after taxonomic revisions and the establishment of a population of Guam rail on Cocos Island, indicates there are now 5 of 16 native terrestrial (non-migratory) birds that remain in the wild on Guam: the Micronesian starling, yellow bittern (not endemic), and three endangered birds (Guam rail, Mariana common moorhen and Mariana swiftlet). The Guam kingfisher exists only in captivity.
Three of the 7 partulid snails described from the Mariana islands are extinct, and the remaining 4 are imperiled. Partulid populations have been affected by invasive snails such as the North American Euglandina species and the New Guinea flatworm (Platydemus manokwari).
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In 2024, USFWS proposed 10 species of clam be protected under the Endangered Species Act (ESA), of which the following are native to the Mariana Islands:
In addition, the fluted giant clam (Tridacna squamosa), is proposed to be listed as endangered. Sources vary as to whether it is an introduced (non-native) or native species in the Marianas, but it remains rare on Guam (<10 individuals per hectare) and is not present in the CNMI. It was determined by the USFWS to not be at risk of extinction in its native range in the foreseeable future, but nonetheless was proposed to be listed as threatened under the ESA due to the similarity of products from this species as from the other species listed above.
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