A rare species is a group of organisms that are very uncommon, scarce, or infrequently encountered. This designation may be applied to either a plant or animal taxon, and is distinct from the term endangered or threatened. Designation of a rare species may be made by an official body, such as a national government, state, or province. The term more commonly appears without reference to specific criteria. The International Union for Conservation of Nature does not normally make such designations, but may use the term in scientific discussion.[1]
Rarity rests on a specific species being represented by a small number of organisms worldwide, usually fewer than 10,000. However, a species having a very narrow endemic range or fragmented habitat also influences the concept.[2] [3] Almost 75% of known species can be classified as "rare".[4]
Rare species are species with small populations. Many will move into the endangered or vulnerable category if the negative factors affecting them continue to operate. Well-known examples of rare species - because these are large terrestrial animals - include the Himalayan brown bear, Fennec fox, Wild Asiatic buffalo, or the Hornbill.
They are not endangered yet, but classified as "at risk",[5] [6] although the frontier between these categories is increasingly difficult to draw given the general paucity of data on rare species. This is especially the case in the world Ocean where many 'rare' species not seen for decades may well have gone extinct unnoticed, if they are not already on the verge of extinction like the Mexican Vaquita.[7]
A species may be endangered or vulnerable, but not considered rare if it has a large, dispersed population. IUCN uses the term "rare" as a designation for species found in isolated geographical locations. Rare species are generally considered threatened because a small population size is less likely to recover from ecological disasters.
Rare plants can be classified based on the size and distribution of their populations. Some species may be rare because they consist of only a few individuals, are confined to a limited geographic area, or both. Certain rare plants are found sparsely distributed across a wide area. Others might have a large number of individuals that are concentrated in a very small area, such as a single county or canyon. The rarest plants typically have both a small number of individuals and a very limited geographic range.
Assessments of the status of rare plants are conducted using the best available data and consider various factors, including:
A rare plant's legal status can be observed through the USDA's Plants Database.
| Common name | Scientific name | Image | Last sighting | International Union for Conservation of Nature Red List of Threatened Species category and criteria | Present estimated wildlife population | Present estimated captive population | Present estimated total population | Endemic geographic location | ||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Ceratotherium simum cottoni | N/A | Critically Endangered (Possibly Extinct in the Wild) A2abcd; C1+2a(i,ii); D | 0 | |||||||||
| Barbary lion | Panthera leo leo | N/A | Extinct in the Wild | 0 | 98 | 98 | Belfast Zoo, IrelandRabat Zoo, MoroccoKeystone Safari, United States | |||||
| Rafetus swinhoei | N/A | Critically Endangered A2acd; D | ||||||||||
| Campephilus principalis principalis | Critically Endangered D | data-sort-value="5" | 1-50 | 0 | data-sort-value="5" | 1-50 | ||||||
| Chelonoidis niger phantasticus | N/A | Critically Endangered (Possibly Extinct) D | data-sort-value="5" | 0-5 | data-sort-value="1" | 1 | data-sort-value="6" | 1-6 | ||||
| Dicerorhinus sumatrensis lasiotis | Critically Endangered A2abd; C1+2a(i) | data-sort-value="9" | 0-9 | 0 | data-sort-value="9" | 0-9 | Tamanthi Wildlife Sanctuary, Myanmar | |||||
| Phocoena sinus | Critically Endangered A2a; C1+2a(ii); D; E | data-sort-value="10" | 6-10 | 0 | data-sort-value="10" | 6-10 | ||||||
| Abies beshanzuensis | N/A | Critically Endangered D | data-sort-value="3" | 3 | data-sort-value="9" | 1-9 | data-sort-value="12" | 4-12 | ||||
| Dicerorhinus sumatrensis harrissoni | N/A | Critically Endangered A2cd+3cd+4cd; C2a(i); D | data-sort-value="14" | 0-14 | data-sort-value="1" | 1 | data-sort-value="15" | 1-15 | ||||
| Encephalartos woodii | N/A | Extinct in the Wild | 0 | data-sort-value="36" | 1-36 | data-sort-value="36" | 1-36 | Kirstenbosch National Botanical Garden, South Africa | ||||
| Loneliest palm | Hyophorbe amaricaulis | N/A | Critically Endangered | ??? | 1 | 1 | Curepipe Botanic Gardens, Mauritius | |||||
| Nomascus hainanus | Critically Endangered A2acd; B1ab(iii); D | data-sort-value="37" | 36-37 | 0 | data-sort-value="37" | 36-37 | ||||||
| Ursus arctos gobiensis | Critically Endangered | data-sort-value="40" | 30-40 | 0 | data-sort-value="40" | 30-40 | ||||||
| Cephalorhynchus hectori maui | Critically Endangered A2cd+4cd; C2a(i,ii); D | data-sort-value="64" | 48-64 | 0 | data-sort-value="64" | 48-64 | ||||||
| Colossal squid | Mesonychoteuthis hamiltoni | 2015 | Least Concern | ??? | 0 | ??? | ||||||
| Rhinoceros sondaicus sondaicus | Critically Endangered D | data-sort-value="81" | 76-80 | 0 | data-sort-value="80" | 76-80 | ||||||
| Dicerorhinus sumatrensis sumatrensis | N/A | Critically Endangered A2cd+3cd+4cd; C2a(i); D | data-sort-value="80" | 30-80 | data-sort-value="8" | 7-8 | data-sort-value="88" | 37-88 | ||||
| Erythrolamprus ornatus | Critically Endangered D | data-sort-value="100" | 18-100 | 0 | data-sort-value="100" | 18-100 | Maria Islands Nature Reserve, Saint Lucia | |||||
| Pseudoryx nghetinhensis | Critically Endangered A2acd+3cd+4acd; C2a(i) | data-sort-value="100" | 20-100 | 0 | data-sort-value="100" | 20-100 | ||||||
| Mitu mitu | N/A | 0 | data-sort-value="100" | 50-100 | data-sort-value="100" | 50-100 | ||||||
| Nothophantes horridus | N/A | Critically Endangered A3c | data-sort-value="99" | 1-99 | data-sort-value="9" | 1-9 | data-sort-value="108" | 2-108 |
| |||
| Trachypithecus poliocephalus | Critically Endangered D | data-sort-value="159" | 130-150 | 0 | data-sort-value="159" | 130-150 | ||||||
| Otus siaoensis | Critically Endangered D | data-sort-value="200" | 50-200 | 0 | data-sort-value="200" | 50-200 | Siau Island, Indonesia | |||||
| Panthera tigris amoyensis | N/A | Critically Endangered (Possibly Extinct in the Wild) | 0 | data-sort-value="200" | 150-200 | data-sort-value="200" | 150-200 | |||||
| Cyprinodon diabolis | N/A | Critically Endangered B1ab(v)+2ab(v); C2a(ii) | data-sort-value="201" | 100-200 | data-sort-value="9" | 1-9 | data-sort-value="200" | 101-209 | Devils Hole, Death Valley National Park, United States of America | |||
| Telmatobius dankoi | N/A | Critically Endangered B1ab(iii)+2ab(iii) | data-sort-value="9" | 1-9 | data-sort-value="214" | 214 | data-sort-value="223" | 215-223 | Small streams along the Loa River southwest of Calama, Chile | |||
| Leptophryne cruentata | Critically Endangered C2a(i) | data-sort-value="249" | 1-249 | 0 | data-sort-value="249" | 1-249 | ||||||
| Black-naped pheasent pigeon | Otidiphaps insularis | September 2022 | Critically Endangered | 50-249 | 0 | 50-249 | Fergusson Island, Papua New Guinea | |||||
| Glyphis gangeticus | Critically Endangered A2cd; C2a(i) | data-sort-value="249" | 1-249 | 0 | data-sort-value="249" | 1-249 | ||||||
| Pink-headed duck | Rhodonessa caryophyllacea | June 1935 | Critically Endangered | 1-49 | 0 | ??? | ||||||
| Pharotis imogene | Critically Endangered D | data-sort-value="249" | 49-249 | 0 | data-sort-value="249" | 49-249 | ||||||
| Crocidura wimmeri | Critically Endangered B1ab(iii) | data-sort-value="250" | 5-250 | 0 | data-sort-value="250" | 5-250 | ||||||
| Heteromirafra archeri | Critically Endangered A3bc; C2a(i) | data-sort-value="250" | 50-250 | 0 | data-sort-value="250" | 50-250 | ||||||
| Cyanopsitta spixii | N/A | Extinct in the Wild | 0 | data-sort-value="300" | 200-300 | data-sort-value="300" | 200-300 | |||||
| Strigops habroptilus | N/A | Critically Endangered A2be | 0 | data-sort-value="300" | 250-300 | data-sort-value="300" | 250-300 | |||||
| Hydrornis gurneyi | Critically Endangered A3c | data-sort-value="300" | 50-300 | data-sort-value="5" | 0-5 | data-sort-value="305" | 55-305 | |||||
| Gorilla gorilla diehli | N/A | Critically Endangered C2a(i) | data-sort-value="300" | 250-300 | data-sort-value="9" | 1-9 | data-sort-value="309" | 251-309 | ||||
| Pithecophaga jefferyi | N/A | Critically Endangered A2cd; C2a(ii) | data-sort-value="300" | 250-300 | data-sort-value="20" | 10-20 | data-sort-value="320" | 260-320 | ||||
| Panthera pardus orientalis | N/A | Critically Endangered C2a(ii); D | data-sort-value="125" | 60-125 | data-sort-value="217" | 217 | data-sort-value="342" | 277-342 | ||||
| Eubalaena glacialis | Critically Endangered C2a(ii) | data-sort-value="400" | 350-400 | 0 | data-sort-value="400" | 350-400 | ||||||
| Nilssonia nigricans | N/A | Critically Endangered A4cd | data-sort-value="499" | 1-499 | data-sort-value="100" | 50-100 | data-sort-value="599" | 51-599 |
| |||
| Gymnogyps californianus | N/A | Critically Endangered C2a(i); D | data-sort-value="350" | 300-350 | data-sort-value="200" | 150-200 | data-sort-value="550" | 450-550 | ||||
| Epioblasma brevidens | N/A | Critically Endangered A1ce | data-sort-value="1000" | 200–1,000 | ? | data-sort-value="1000" | 200-1,000 | |||||
| Cryptochloris wintoni | N/A | Critically Endangered (Possibly Extinct) B1ab(iii)+2ab(iii) | data-sort-value="999" | 1-999 | data-sort-value="9" | 1-9 | data-sort-value="1008" | 2-1,008 | ||||
| Dryococelus australis | N/A | Critically Endangered D | data-sort-value="49" | 1-49 | data-sort-value="1000" | 500–1,000 | data-sort-value="1049" | 501-1,049 | Ball's Pyramid, Australia | |||
| Camelus ferus | N/A | Critically Endangered A3de+4ade | data-sort-value="1500" | 1,000-1,500 | data-sort-value="199" | 100-200 | data-sort-value="1700" | 1,100-1,700 | ||||
| Pilosocereus robinii | N/A | Extinct in the Wild | 0 | data-sort-value="1999" | 200–2,000 | data-sort-value="1999" | 200-2,000 |
| ||||
| Zyzomys pedunculatus | N/A | Critically Endangered A2abce | data-sort-value="2000" | 500–2,000 | data-sort-value="9" | 1-9 | data-sort-value="2000" | 501-2,009 | ||||
| Gorilla beringei graueri | N/A | Critically Endangered A4bcd | data-sort-value="5000" | 3,800-5,000 | data-sort-value="19" | 1-19 | data-sort-value="5019" | 3,801-5,019 |