Rare species

Group of organisms that are very uncommon, scarce, or infrequently encountered

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:

Total number of occurrences and the condition of these populations
Population size
Extent of range and area occupied
Trends in population size and distribution over the short and long term
Nature, severity, and urgency of threats
Number of occurrences that are protected and actively managed
Intrinsic vulnerability of the species
Specificity to environmental conditions^[8]

A rare plant's legal status can be observed through the USDA's Plants Database.

Critically Endangered, Possibly Extinct

Common name	Scientific name	Last sighting	Estimated population of mature individuals	Endemic geographic location
Gloomy tube-nosed bat	Murina tenebrosa	1962	0-1	Tsushima Island & Yakushima, Japan
Emperor rat	Uromys imperator	1959 or prior	0-3
Guadalcanal rat	Uromys porculus	1888	0-3
One-striped opossum	Monodelphis unistriata	9 April 1899	0-10
Baiji	Lipotes vexillifer	14 May 2024	0-19
Glacous macaw	Anodorhynchus glaucus	1951	0-20
Angel Island mouse	Peromyscus guardia	1991	0-49
Aru flying fox	Pteropus aruensis	1867	0-49	Trangan, Indonesia
Cuban ivory-billed woodpecker	Campephilus principalis bairdii	28 April 1987	0-49	Cuba
Emma's giant rat	Uromys emmae	1994	0-49	Owi Island, Indonesia
Ethiopian amphibious rat	Nilopegamys plumbeus	1928	0-49
Garrido's hutia	Capromys garridoi	1989	0-49	Banco de los Jardins y Jardinillos, Canarreos Archipelago, Cuba
Zuniga's melanomys	Melanomys zunigae	1949	0-49	Lima Department, Peru
Dwarf hutia	Mesocapromys nana	26 October 1951	0-50	Zapata Swamp, Cuba
New Zealand greater short-tailed bat	Mystacina robusta	23 January 1967	0-50
Puebla deer mouse	Peromyscus mekisturus	1948	0-50
Kouprey	Bos sauveli	1988	0-50
Montane monkey-faced bat	Pteralopex pulchra	17 May 1990	0-50
San Felipe hutia	Mesocapromys sanfelipensis	1978	0-99	Cayo de Juan Garcia & Cayos de San Felipe, Cuba
Christmas Island shrew	Crocidura trichura	1998	0-200
Malabar large-spotted civet	Viverra civettina	1993	0-249

Critically Endangered / Extinct in the Wild

Common name	Scientific name	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
Northern white rhinoceros	Ceratotherium simum cottoni	N/A	Critically Endangered (Possibly Extinct in the Wild) A2abcd; C1+2a(i,ii); D	0	2	2
Yangtze giant softshell turtle	Rafetus swinhoei	N/A	Critically Endangered A2acd; D	2	1	3
American ivory-billed woodpecker	Campephilus principalis principalis	8 April 2022	Critically Endangered D	0-5	0	0-5
Fernandina Island Galápagos tortoise	Chelonoidis niger phantasticus	N/A	Critically Endangered (Possibly Extinct) D	0-5	1	1-6
Northern Sumatran rhinoceros	Dicerorhinus sumatrensis lasiotis	1993	Critically Endangered A2abd; C1+2a(i)	0-9	0	0-9	Tamanthi Wildlife Sanctuary, Myanmar
Vaquita	Phocoena sinus	May 2024	Critically Endangered A2a; C1+2a(ii); D; E	6-10	0	6-10
Baishanzu fir	Abies beshanzuensis	N/A	Critically Endangered D	3	1-9	4-12
Bornean rhinoceros	Dicerorhinus sumatrensis harrissoni	N/A	Critically Endangered A2cd+3cd+4cd; C2a(i); D	0-14	1	1-15	East Kalimantan, Indonesia Sarawak, Malaysia
Wood's cycad	Encephalartos woodii	N/A	Extinct in the Wild	0	1-36	1-36	Kirstenbosch National Botanical Garden, South Africa
Hainan black crested gibbon	Nomascus hainanus	2023	Critically Endangered A2acd; B1ab(iii); D	36-37	0	36-37
Gobi bear	Ursus arctos gobiensis	12 April 2023	Critically Endangered	30-40	0	30-40
Māui dolphin	Cephalorhynchus hectori maui	28 January 2023	Critically Endangered A2cd+4cd; C2a(i,ii); D	48-64	0	48-64
Indonesian Javan rhinoceros	Rhinoceros sondaicus sondaicus	17 March 2023	Critically Endangered D	76-80	0	76-80
Western Sumatran rhinoceros	Dicerorhinus sumatrensis sumatrensis	N/A	Critically Endangered A2cd+3cd+4cd; C2a(i); D	30-80	7-8	37-88
Ornate Ground snake	Erythrolamprus ornatus	2012	Critically Endangered D	18-100	0	18-100	Maria Islands Nature Reserve, Saint Lucia
Saola	Pseudoryx nghetinhensis	August 2013	Critically Endangered A2acd+3cd+4acd; C2a(i)	20-100	0	20-100
Alagoas curassow	Mitu mitu	N/A	Extinct in the Wild	0	50-100	50-100
Horrid ground-weaver	Nothophantes horridus	N/A	Critically Endangered A3c	1-99	1-9	2-108	Billacombe Quarry, Plymstock, Plymouth, United Kingdom of Great Britain and Northern Ireland (UK) Plymouth Trade Park, Cattedown, Plymouth, UK Radford Quarry, Plymstock, Plymouth, UK
Cat Ba langur	Trachypithecus poliocephalus	8 November 2022	Critically Endangered D	130-150	0	130-150
Siau scops owl	Otus siaoensis	2017	Critically Endangered D	50-200	0	50-200	Siau Island, Indonesia
South China tiger	Panthera tigris amoyensis	N/A	Critically Endangered (Possibly Extinct in the Wild)	0	150-200	150-200
Devils Hole pupfish	Cyprinodon diabolis	N/A	Critically Endangered B1ab(v)+2ab(v); C2a(ii)	100-200	1-9	101-209	Devils Hole, Death Valley National Park, United States of America
Loa water frog	Telmatobius dankoi	N/A	Critically Endangered B1ab(iii)+2ab(iii)	1-9	214	215-223	Small streams along the Loa River southwest of Calama, Chile
Bleeding toad	Leptophryne cruentata	2003	Critically Endangered C2a(i)	1-249	0	1-249	Mount Gede Pangrango National Park, Indonesia (ID) Mount Halimun Salak National Park, ID
Black-naped pheasent pigeon	Otidiphaps insularis	September 2022	Critically Endangered	50-249	0	50-249	Fergusson Island, Papua New Guinea
Ganges shark	Glyphis gangeticus	February 2016	Critically Endangered A2cd; C2a(i)	1-249	0	1-249
New Guinea big-eared bat	Pharotis imogene	March 2014	Critically Endangered D	49-249	0	49-249
Wimmer's shrew	Crocidura wimmeri	1988	Critically Endangered B1ab(iii)	5-250	0	5-250
Archer's lark	Heteromirafra archeri	2003	Critically Endangered A3bc; C2a(i)	50-250	0	50-250
Spix's Macaw	Cyanopsitta spixii	N/A	Extinct in the Wild	0	200-300	200-300
Kākāpō	Strigops habroptilus	N/A	Critically Endangered A2be	0	250-300	250-300	Anchor Island, New Zealand (NZ) Codfish Island / Whenua Hou, NZ Little Barrier Island, NZ Maud Island, NZ Sanctuary Mountain Maungatautari, NZ
Gurney's pitta	Hydrornis gurneyi	2016	Critically Endangered A3c	50-300	0-5	55-305	Portions of south central Karathuri Subtownship, Bokepyin Township, Bokepyin District, Tanintharyi Region, Myanmar Portions of northwestern Kawthoung Township, Kawthaung District, Tanintharyi Region, MM Portion of east central Myeik Township, Myeik District, Tanintharyi Region, MM Portions of south central Pyigyimandaing Subtownship, Bokepyin Township, Bokepyin District, Tanintharyi Region, MM Portions of north central and southwestern Tanintharyi Township, Myeik District, Tanintharyi Region, MM Portions of southwestern Ao Tong, Wang Wiset district, Trang province, Thailand (TH) Portions of east central Bang Rup, Tham Phannara district, Nakhon Si Thammarat province, TH Portions of southwestern Dusit subditrict, Tham Phannara district, Nakhon Si Thammarat province, TH Portions of northern Kalase, Wang Wiset district, Trang province, TH Portions of eastern Khlong Phon, Krabi province, TH Portions of northeastern Sai Khao, Krabi province, TH Portions of western Tham Phannara subdistrict, Tham Phannara district, Nakhon Si Thammarat province, TH Portions of northwestern Thung Sang, Thung Yai district, Nakhon Si Thammarat province, TH
Cross River gorilla	Gorilla gorilla diehli	N/A	Critically Endangered C2a(i)	250-300	1-9	251-309
Philippine eagle	Pithecophaga jefferyi	N/A	Critically Endangered A2cd; C2a(ii)	250-300	10-20	260-320
Amur leopard	Panthera pardus orientalis	N/A	Critically Endangered C2a(ii); D	60-125	217	277-342
North Atlantic right whale	Eubalaena glacialis	22 August 2023	Critically Endangered C2a(ii)	350-400	0	350-400
Black softshell turtle	Nilssonia nigricans	N/A	Critically Endangered A4cd	1-499	50-100	51-599	Brahmaputra River floodplain, Assam, India (IN) Kaziranga National Park, IN Nameri National Park, IN Temple ponds of the Nagsankar Mandir, Sootea, Tezpur, IN Temple ponds of the Shrine of Bayazid Bostami, Chittagong, Bangladesh
California condor	Gymnogyps californianus	N/A	Critically Endangered C2a(i); D	300-350	150-200	450-550
Cumberlandian combshell	Epioblasma brevidens	N/A	Critically Endangered A1ce	200-1,000	?	200-1,000
De Winton's golden mole	Cryptochloris wintoni	N/A	Critically Endangered (Possibly Extinct) B1ab(iii)+2ab(iii)	1-999	1-9	2-1,008
Lord Howe Island stick insect	Dryococelus australis	N/A	Critically Endangered D	1-49	500-1,000	501-1,049	Ball's Pyramid, Australia
Wild Bactrian camel	Camelus ferus	N/A	Critically Endangered A3de+4ade	1,000-1,500	100-200	1,100-1,700
Key tree-cactus	Pilosocereus robinii	N/A	Extinct in the Wild	0	200-2,000	200-2,000	Royal Botanic Gardens, Kew, United Kingdom of Great Britain and Northern Ireland Missouri Botanical Garden, United States of America (US) San Diego Zoo Global's Botanic Garden, US
Central rock rat	Zyzomys pedunculatus	N/A	Critically Endangered A2abce	500-2,000	1-9	501-2,009
Eastern lowland gorilla	Gorilla beringei graueri	N/A	Critically Endangered A4bcd	3,800-5,000	1-19	3,801-5,019

References

^ "Assessment Process". www.iucnredlist.org. Retrieved 2017-11-14.
^ R. MacNally and G. W. Brown, Reptiles and Habitat Fragmentation in the Box-ironbush Forests of Central Victoria, Australia: Predicting Compositional Change and Faunal Nested-ness, Oecologia 128:116–125 (2001).
^ Prendergast, J. R.; Quinn, R. M.; Lawton, J. H.; Eversham, B. C.; Gibbons, D. W. (1993-09-23). "Rare species, the coincidence of diversity hotspots and conservation strategies". Nature. 365 (6444): 335–337. Bibcode:1993Natur.365..335P. doi:10.1038/365335a0.
^ Dinerstein, Eric (2013) The Kingdom of Rarities. Island Press. ISBN 9781610911955.
^ "Rare Species". www.encyclopedia.com. Retrieved 2017-11-15.
^ "IUCN – A brief history". IUCN. 2017-10-06. Archived from the original on 2017-11-15. Retrieved 2017-11-15.
^ Briand, Frederic (October 2012). "Species Missing in Action - Rare or Already Extinct?". National Geographic.
^ "What is a rare plant?". www.fs.usda.gov. Retrieved 2024-04-12.