Small populations can behave differently from larger populations. They are often the result of a population bottlenecks from larger populations, leading to loss of heterozygosity and reduced genetic diversity and loss or fixation of alleles and shifts in allele frequencies. A small population is then more susceptible to demographic and genetic stochastic events, which can impact the long-term survival of the population. Therefore, small populations are often considered at risk of endangerment or extinction, and are often of conservation concern.
The influence of stochastic variation in demographic (reproductive and mortality) rates is much higher for small populations than large ones. Stochastic variation in demographic rates causes small populations to fluctuate randomly in size. This variation could be a result of unequal sex ratios, high variance in family size, inbreeding or fluctuating population size. The smaller the population the greater the probability that fluctuations will lead to extinction.
One demographic consequence of a small population size is the probability that all offspring in a generation are of the same sex, and where males and females are equally likely to be produced (see sex ratio), is easy to calculate: it is given by (The chance of all animals being females is ; the same holds for all males, thus this result). This can be a problem in very small populations. In 1977, the last 18 kakapo on a Fiordland island in New Zealand were all male, though the probability of this would only be 0.0000076 if determined by chance (however, females are generally preyed upon more often than males and kakapo may be subject to sex allocation). With a population of just three individuals the probability of them all being the same sex is 0.25. Put another way, for every four species reduced to three individuals (or more precisely three individuals in the effective population), one will become extinct within one generation just because they are all the same sex. If the population remains at this size for several generations, such an event becomes almost inevitable.
The environment can directly affect the survival of a small population. Some detrimental effects include stochastic variation in the environment, (year to year variation in rainfall, temperature) which can produce temporally correlated birth and death rates (i.e. 'good' years when birth rates are high and death rates are low and 'bad' years when birth rates are low and death rates are high) that lead to fluctuations in the population size. Again, smaller populations are more likely to become extinct due to these environmentally generated population fluctuations than the large populations.
The environment can also introduce beneficial traits to a small population that promote its persistence. In the small, fragmented populations of the acorn woodpecker, minimal immigration is sufficient for population persistence. Despite the potential genetic consequences of having a small population size, the acorn woodpecker is able to avoid extinction and the classification as an endangered species because of this environmental intervention causing neighboring populations to immigrate. Immigration promotes survival by increasing genetic diversity, which will be discussed in the next section as a harmful factor in small populations.
Conservationists are often worried about a loss of genetic variation in small populations. There are two types of genetic variation that are important when dealing with small populations:
Genetic drift and the likelihood of inbreeding tend to have greater impacts on small populations, which can lead to speciation. Both drift and inbreeding cause a reduction in genetic diversity, which is associated with a reduced population growth rate, reduced adaptive potential to environmental changes, and increased risk of extinction. The effective population size (Ne), or the reproducing part of a population is often lower than the actual population size in small populations. The Ne of a population is closest in size to the generation that had the smallest Ne. This is because alleles lost in generations of low populations are not regained when the population size increases. For example, the Northern Elephant Seal was reduced to 20-30 individuals, but now there are 100,000 due to conservation efforts. However the effective population size is only 60.
Examples of genetic consequences that have happened in inbred populations are bone abnormalities, low infant survivability, and decrease in birth rates. Some populations that have these consequences are cheetahs, who suffer with low infant survivability and a decrease in birth rate due to having gone through a population bottleneck. Northern elephant seals, who also went through a population bottleneck, have had cranial bone structure changes to the lower mandibular tooth row. The wolves on Isle Royale, a population restricted to the island in Lake Superior have bone malformations in the vertebral column in the lumbosacral region. These wolves also have syndactyly, which is the fusion of soft tissue between the toes of the front feet. These types of malformations are caused by inbreeding depression or genetic load.
Island populations often also have small populations due to geographic isolation, limited habitat and high levels of endemism. Because their environments are so isolated gene flow is poor within island populations. Without the introduction of genetic diversity from gene flow, alleles are quickly fixed or lost. This reduces island populations' ability to adapt to any new circumstances and can result in higher levels of extinction. The majority of mammal, bird, and reptile extinctions since the 1600s have been from island populations. Moreover, 20% of bird species live on islands, but 90% of all bird extinctions have been from island populations. Human activities have been the major cause of extinctions on island in the past 50,000 years due to the introduction of exotic species, habitat loss and over-exploitation
The Galapagos penguin is an endangered endemic species of the Galapagos islands. Its population has seen extreme fluctuations in population size due to marine perturbations, which have become more extreme due to climate change. The population has ranged from as high as 10,000 specimens to as low as 700. Currently it is estimated there are about 1000 mature individuals.
Conservation efforts for small populations at risk of extinction focus on increasing population size as well as genetic diversity, which determines the fitness of a population and its long-term persistence. Some methods include captive breeding and genetic rescue. Stabilizing the variance in family size is an effective way can double the effective population size and is often used in conservation strategies.
The Auckland shag (Leucocarbo colensoi) or Auckland Islands shag is a species of cormorant from New Zealand. The species is endemic to the Auckland Islands archipelago. It is a sedentary bird that primarily eats various crustaceans and fish. In recent years, roughly 1,000 pairs have been recorded. The Auckland shag is a colonial nester, building sizeable nests of, among other items, grass, twigs and seaweed. The Auckland shag lays three pale blue-green eggs in November–February. The incubation period is 26–32 days.
The Auckland shag is considered Vulnerable by the IUCN due to its small population size and restricted global range. Only around 2000 Auckland shags exist in their remote habitat.
Some taxonomic authorities, including the International Ornithologists' Union, place this species in the genus Leucocarbo. Others place it in the genus Phalacrocorax.
The binomial name of this bird commemorates the naturalist William Colenso.Bawean deer
The Bawean deer (Hyelaphus kuhlii), also known as Kuhl's hog deer or Bawean hog deer, is a highly threatened species of deer found only in the island of Bawean (Gresik Regency) in Indonesia.
A typical height for males of 60–70 cm has been reported. Males have three-tined antlers.
Their fawns are spotted at birth, which separates them from the best known western population of the hog deer (H. porcinus).
Due to ongoing habitat loss, small population size and limited range, the Bawean deer is evaluated as critically endangered on the IUCN Red List of Threatened Species. It is listed on Appendix I of CITES. It has few natural enemies except for birds of prey and large snakes such as pythons.Black-winged lory
The black-winged lory (Eos cyanogenia) also known as Biak red lory is a medium-sized, about 30 cm (12 in) long, long-tailed lory. It has a bright red plumage, black shoulder, red iris, an orange red bill and violet ear-patch behind eye. The underwings are red, becoming yellowish with black tips. Both sexes are similar.
An Indonesian endemic, the black-winged lory is distributed to forests and coastal habitat of Biak, Numfoor, and Mios Num islands in Cenderawasih Bay, Papua. It frequents and roosts in coconut trees.
Due to ongoing habitat loss, small population size and hunted in some areas, the black-winged lory is evaluated as Vulnerable on IUCN Red List of Threatened Species. It is listed on Appendix II of CITES.Black partridge
The black partridge (Melanoperdix niger), also known as the black wood partridge, is a small (up to 27 cm long) partridge with a thick bill, grey legs and dark brown iris. It is the only member of the monotypic genus Melanoperdix.
The black partridge is sexually dimorphic. The male has entirely glossy black plumage and a black bill, while the female is generally a chestnut-brown bird with a whitish throat and belly and a dark horn-colored bill. The female is smaller than the male.
The black partridge occurs in lowland rainforests of Peninsular Malaysia, Borneo and Sumatra in southeast Asia. It was formerly found but is long extinct on Singapore. The female usually lays five to six white eggs.
Due to ongoing habitat loss, small population size and overhunting in some areas, the black partridge is evaluated as Vulnerable on the IUCN Red List of Threatened Species. It is listed on Appendix III of CITES in Malaysia.Black sicklebill
The black sicklebill (Epimachus fastosus) is a large bird-of-paradise of midmountain forests of New Guinea.
The sicklebill's diet consists mainly of fruits and arthropods. The male of the species is polygamous and performs a horizontal courtship display with the pectoral plumes raised around its head.
In the wild, the bird has hybridised with the Arfak astrapia to create offspring that were once considered two distinct species, the Elliot's sicklebill (Epimachus ellioti) and the astrapian sicklebill (Astrapimachus astrapioides). Both species are generally viewed by most mainstream ornithologists as hybrids, but a minority of ornithologists believe ellioti may be a valid species.
Ongoing habitat loss, small population size, and hunting in some areas for food and its tail feathers are areas of concern. The black sicklebill is classified as Least Concern on the IUCN Red List of Threatened Species. It is listed on Appendix II of CITES.Blue bird-of-paradise
The blue bird-of-paradise (Paradisaea rudolphi) is a medium-sized bird-of-paradise.
Regarded by some ornithologists as the loveliest of all birds, the blue bird-of-paradise was discovered by Carl Hunstein in 1884. The scientific name commemorates the ill-fated Crown Prince Rudolf of Austria.
Due to ongoing habitat loss, limited range, small population size and, in some areas, by hunting for its highly prized plumes, the rare blue bird-of-paradise is classified as Vulnerable on the IUCN Red List of Threatened Species. It is listed on Appendix II of CITES.British Virgin Islands national basketball team
The British Virgin Islands national basketball team represents the British Virgin Islands (BVI) in international basketball competitions. It is administrated by the British Virgin Islands Amateur Basketball Federation.Despite their very small population size, the BVI are one of the top contenders at the Caribbean Basketball Championship as they finished in the top four at the last four competitions. Their best result was runner-up at the 2009 edition.Depensation
In population dynamics, depensation is the effect on a population (such as a fish stock) whereby, due to certain causes, a decrease in the breeding population (mature individuals) leads to reduced production and survival of eggs or offspring. The causes may include predation levels rising per offspring (given the same level of overall predator pressure) and the allee effect, particularly the reduced likelihood of finding a mate.Elegant sunbird
The elegant sunbird (Aethopyga duyvenbodei) is a large, up to 12 cm long, Australasian sunbird in the genus Aethopyga. The male has an iridescent blue-green crown, shoulder patch and uppertail coverts, yellow bar across lower back, red ear coverts, olive back, yellow throat, red neck collar and yellow below. The female has a yellowish olive upperparts, scaly crown and yellow underparts.
The scientific name commemorates Maarten Dirk van Renesse van Duivenbode (1804-1878), Dutch trader of naturalia on Ternate.
An Indonesian endemic, the elegant sunbird is distributed to the island of Sangihe, north of Sulawesi. It is found and locally common in the forests and plantations near Mount Sahendaruman in southern Sangihe.
Due to ongoing habitat loss, small population size and limited range, the elegant sunbird is evaluated as Endangered on the IUCN Red List of Threatened Species.Fuzhou people
The people of Fuzhou (Chinese: 福州人; Foochow Romanized: Hók-ciŭ-nè̤ng), also known as Fuzhounese, Foochowese, Hokchew, Hokchia, Hokchiu, Fuzhou Shiyi people (福州十邑人), Eastern Min or Mindong usually refers to people who originate from Fuzhou region and the Mindong region, adjacent Gutian County, Pingnan County, in Fujian province and in the adjacent Matsu Islands. Fuzhounese are Han Chinese people and are a part of Min-speaking group, who speaks Eastern Min or specifically Fuzhou dialect. There is also a significant overseas Foochowese population, particularly distributed in Malaysia, Indonesia, Singapore, United States (Fuzhou Americans), Japan, United Kingdom, etc.Despite their small population size, Fuzhounese people have produced a large number of achievements in both academic and science fields, there has been 17 Fuzhounese Zhuangyuans (scholar who is ranked first in the imperial examinations), and famous mathematicians and scientists such as Zhang Yuzhe (the father of modern Chinese astronomy), Guo Kexin (the main pioneer of electron microscopy of China), Chih-Tang Sah, Hsien Wu, Guo Kexin and Min Zhuo are Fuzhounese.Hoogerwerf's pheasant
The Hoogerwerf's pheasant (Lophura hoogerwerfi) also known as Aceh pheasant or Sumatran pheasant is a medium-sized, up to 55 centimetres (22 in) long, bird of the family Phasianidae. The male is a crestless bluish black pheasant with bare red facial skin, short tail and grey legs. The female is a rufous brown bird with a dark bluish grey legs and short dark tail.
Its appearance resembles, and sometimes it is considered as a subspecies of the Salvadori's pheasant. The female is different from the latter for having darker brown, lack of buff mottling and plainer plumage.
An Indonesian endemic, this little-known pheasant inhabits to mid-mountain forests of Gunung Leuser National Park in Aceh province. Previously known only from two female specimens, it was recently discovered in a market in Medan, North Sumatra.
The name commemorates the Dutch ornithologist and taxidermist Andries Hoogerwerf.
Due to ongoing habitat loss, small population size and limited range, the Hoogerwerf's pheasant is evaluated as Vulnerable on the IUCN Red List of Threatened Species.Horned guan
The horned guan (Oreophasis derbianus) is a large, approximately 85 cm long, turkey-like bird with glossed black upperparts plumage, red legs, white iris, yellow bill and a red horn on top of head. The breast and upper belly are white, and its long tail feathers are black with white band near base. Both sexes are similar. The young is duller with smaller horn, and has brown tail and wings.
The only member in monotypic genus Oreophasis, the horned guan is distributed in humid mountain forests of southeast Mexico-(Chiapas) and Guatemala of Central America. It is found in altitude up to 3,350 metres. Its diet consists mainly of fruits, green leaves and invertebrates. The female usually lays up to two eggs.
The horned guan is not a true guan, but merely resembles these birds most in overall shape and color, whereas the horn is more reminiscent of the helmeted curassows. In fact, this species is the only survivor of a very ancient lineage of cracids that has been evolving independently from all other living members of this family for at least 20, possibly as much as 40 million years.
Although it does not have any really close relatives among living cracids, the true guans are apparently most distant. Given that the basal relationships of the living cracids are not well resolved, the horned guan is often placed into a distinct subfamily, the Oreophasinae. Alternatively, it might be included in a large Cracinae with curassows and chachalacas (Pereira et al. 2002)
Due to ongoing habitat loss, small population size, limited range and hunting in some areas, the horned guan is evaluated as Endangered on the IUCN Red List of Threatened Species. It is listed on Appendix I of CITES.Media of Mauritius
The media of Mauritius is limited by its small population size (estimated at 1,288,000 in 2008). Nonetheless, Mauritius has a robust economy, and there are a number of major media outlets, including print newspapers, radio and television stations.Papuan eagle
The Papuan eagle (Harpyopsis novaeguineae) also known as the Papuan harpy eagle, New Guinea eagle, or Kapul eagle, is a large (length 75–90 cm, wingspan 157 cm, weight 1600–2400 g) greyish brown raptor with a short full crest, broad three-banded wings, powerful beak, large iris, long rounded tail and white underparts. It has long and powerful unfeathered legs with sharp claws. The sexes are similar, and the female is slightly larger than the male. It is the only member of the genus Harpyopsis.
The Papuan eagle is endemic to undisturbed tropical rainforests of New Guinea, where it became the top predator of the island after the extinction of local giant monitor lizards and possibly Thylacoleo. The diet consists mainly of phalangers or Kapul in a local language, hence its alternative name. It also feeds on other mammals, birds and snakes. Singing dogs are known to steal the bird's kills; in turn, the canids are part of the bird's diet.One of a group of four large eagles, the others being the crested and harpy eagle of South America and the Philippine eagle of the Philippines (although the latter may be more closely related to species of snake eagle around the world), the New Guinea harpy eagle is essentially a mountain bird that nests in high forest trees, but may be found down to sea level in the few places where forests remain undisturbed.
Due to ongoing habitat loss, small population size, and hunting for its feathers which are used on ceremonial occasions, the Papuan eagle is evaluated as Vulnerable on the IUCN Red List of Threatened Species. It is listed on Appendix II of CITES.Phoenix petrel
The Phoenix petrel (Pterodroma alba) is a medium-sized tropical seabird, measuring up to 35 cm (14 in) long, with a wingspan of 83 cm (33 in). It has a dark brown upperparts plumage, white below and whitish throat. The sexes are similar.
The Phoenix petrel is found throughout oceans and coastal areas in the central Pacific Ocean. Their colonies can be found on Phoenix, Tonga, Kiritimati, Tuamotu, Marquesas and Pitcairn Island. Females lay one white egg on the ground surface. The diet consists mainly of squid, fish and crustaceans.
Due to ongoing habitat loss, small population size, predation by invasive species and human exploitation, the Phoenix petrel is evaluated as endangered on the IUCN Red List of Threatened Species.Rare species
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 IUCN does not normally make such designations, but may use the term in scientific discussion.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. Almost 75% of known species can be classified as "rare."The International Union for Conservation of Nature uses the term "rare" as a designation for species found in isolated geographical locations. They are not endangered but classified as "at risk."A species may be endangered or vulnerable, but not considered rare if it has a large, dispersed population. Rare species are generally considered threatened because a small population size is more likely to not recover from ecological disasters.Rare species are species with small populations. Many move into the endangered or vulnerable category if the negative factors affecting them continue to operate. Examples of rare species include the Himalayan brown bear, Fennec fox, Wild Asiatic buffalo and Hornbill.
A rare plant's legal status can be observed through the USDA's Plants Database.Słońsk
Słońsk pronounced [swɔɲsk] (German: Sonnenburg) is a village in Sulęcin County of the Lubusz Voivodeship, in western Poland. It is located 12 kilometres (7.5 mi) east of the border crossing with Germany along national road DK22. The village lies about 25 kilometres (or 16 miles) northwest of Sulęcin and 36 kilometres (22 mi) southwest of Gorzów Wielkopolski.
The village borders Poland's Ujście Warty National Park stretching to the north. Słońsk had town privileges from 1808 to 1947, consequence of a small population size. During the Second World War, Słońsk (Sonnenburg) was the site of a Nazi concentration camp, now a museum.Udzungwa forest partridge
The Udzungwa forest partridge (Xenoperdix udzungwensis) also known as Udzungwa partridge is a small, approximately 29 centimetres (11 in) long, boldly barred, brownish partridge with rufous face, grey underparts, olive-brown crown and upperparts. It has a red bill, brown iris and yellow legs. Both sexes are similar.
Discovered only in 1991, this bird was first noticed as a pair of strange feet in a cooking pot in a Tanzanian forest camp. It inhabits and is endemic to forests of the Udzungwa Mountains in Tanzania. A second population from the Rubeho Highlands was initially believed to be a well-marked subspecies, but is now recognized to be specifically distinct. The diet consists mainly of beetles, ants and seeds.
Due to ongoing habitat loss, small population size, limited range and overhunting in some areas, the Udzungwa forest partridge is classified as Endangered on the IUCN Red List of Threatened Species.Waigeo brushturkey
The Waigeo brushturkey or Bruijn's brushturkey (Aepypodius bruijnii) is a large (approximately 43 cm long) brownish-black megapode with a bare red facial skin, red comb, maroon rump and chestnut brown below. There are two elongated red wattles on the back of the head and a long wattle on the foreneck. Both sexes are similar. The female has a smaller comb and no wattles.
An Indonesian endemic, the Waigeo brushturkey occurs in mountain forests on Waigeo Island of West Papua.
Previously known from less than twenty-five specimens, this little-known species was relocated in 2002. The name commemorates the Dutch merchant Anton August Bruijn.
This bird is threatened by hunting, ongoing habitat loss, small population size and a limited range. It was formerly classified as a Vulnerable species by the IUCN. But new research has shown it to be rarer than it was believed. Consequently, it was uplisted to Endangered status in 2008.
Effects of selection
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