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Conservation, disease, education, grey squirrel, invasive, nature, red squirrel, UK, wildlife
The red squirrel (Sciurus vulgaris) is native to the UK and could historically be found in both coniferous and deciduous woodlands, though it is now almost exclusively found in the former. It is primarily an arboreal species, feeding on a range of seeds and nuts during the warmer months before spending much of the winter in a state of torpor. Populations of S. vulgaris have declined markedly across most the UK since the 1930’s with current population estimates hovering around 160,000. Around 75% of these occur in Scotland with the other 25% being found in isolated patches throughout England and Wales. The reasons for this decline are threefold: i) extensive fragmentation and loss of suitable habitat, ii) inter-specific competition with and iii) transmission of the parapox virus from the introduced North American grey squirrel (S. caroliniensis) which now numbers in the region of 2.5 million.
A survey carried out in Northern Ireland on red and grey squirrel habitat associations showed a specific distinction in preference between species for coniferous or deciduous forests. Red squirrels occupied predominantly large coniferous forests at higher latitudes than the lower deciduous forests favoured by greys which are also more tolerant of smaller forest fragments. More specifically, reds were found to require a mature canopy and a large number of trees of cone-bearing age. Such optimum conditions may not be met in managed forests where the age of trees and harvesting methods employed result in a relative scarcity of mature stands. Where there is sufficient food, red squirrels may also be found in predominantly deciduous woodland though such instances are in the extreme minority.
It is well documented that squirrel poxvirus (SQPV), a pustular dermatitis, is a major threat to red squirrel populations. Though the origin of the disease is unknown (indeed, it may have been present in the population prior to the introduction of grey squirrels), it is widely accepted that grey squirrels are the main vector for its transmission. While SQPV is not carried by all grey squirrels and is only pathogenic to a small minority, it has a very high mortality in reds. SQPV is particularly virulent, resulting in the death of the majority of red squirrel hosts within two weeks. This results in a swift community shift where the disease is introduced, with greys rapidly replacing reds. SQPV presents in a similar way to mixomatosis in rabbits: lethargy, poor coordination and facial lesions all manifest within two weeks of infection. It is possible to treat SQPV if caught at early enough, though if a squirrel is identified as having SQPV at any stage, it must be immediately removed from the population.
Control of grey squirrel populations is problematic at best. They are such an established species within the British countryside that many regard them as perhaps more integral and identifiable than the native red. Such widespread acceptance both highlights the speed with which the grey squirrel has spread across the UK and is indicative of the probable response to extreme and widespread actions such as culls. The best and most obvious course of action would be to arrest the spread of grey squirrels into areas inhabited by red squirrels. Supplementary feeding of red squirrels to the exclusion of greys could possibly bolster the red population and provide stability.
The long-term control and exclusion of grey squirrels may not be entirely feasible; the adaptability and fecundity of the species means that any form of control is likely to be costly and the benefits debatable. Despite this, the preservation of mainland red squirrel populations depends on minimising the impact of greys on prime red squirrel habitat. While control measures should be implemented, of greater importance is the management of forest habitat to favour red squirrels and the identification and utilisation of a vaccine against SQPV.
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Little studied, this small deer inhabits dense upland forests of Bawean Island, Indonesia, an area of 200km2. This represents the most restricted range of any deer species. Morphologically similar to the India’s closely related hog deer, they are a little-seen species due to their largely nocturnal habits. The total wild population is thought to be around 250 individuals. Predators including wild pigs, macaques and pythons may account for some individuals but their impact is likely to be minimal. Feral dogs pose a far greater threat and, along with habitat loss and a decline in habitat quality, are the main causes of continued decline.
Also called the ‘Pygmy raccoon’, P. pygmaeus is much smaller and occurs over a far smaller range than its better-known cousin, the common raccoon (Procyon lotor). Their insular dwarfism is due to their isolation and evolution on Cozumel Island, Mexico. P. pygmaeus is thought to exhibit more specific ecological requirements than P. lotor and island-raccoon subspecies. They prefer mangrove and wetland habitats where they forage for crabs and shellfish. Such specificity in an island species inevitably limits the extent of occurrence (478km2) and population size. Indeed, there are fewer than 250 mature individuals remaining. Anthropogenic factors and the impact of hurricanes – which can account for 60% of juveniles – pose the greatest threats.
A subspecies of Hector’s dolphin, Maui’s dolphin (originally called the North Island Hector’s dolphin) is found along the West coast of North Island, New Zealand. They are largely threatened by gillnet and trawl fisheries where it they are caught as bycatch, pollution, boat strikes and inbreeding. Maui’s conform to the common dolphin stereotypes of sociability and playfulness, grouping in pods over five strong. They have a slow reproductive cycle with females calving every 2-4 years and then only producing a single offspring. Approximately 111 individuals remain. Only 28 of these are likely to be mature females.
S. cebifrons is a gregarious pig which is endemic to the Visayan island chain – more specifically the islands of Panay, Negros and possibly Masbate – in the Philippines. The species are easily distinguished by the white band running laterally across the top of the nose which is present in both sexes. Little is known of their ecology though it is likely that in ideal circumstances it is an overall generalist. The remaining populations are fragmented, having been extirpated in 95% of the historical range by slash-and-burn agriculture, logging, hunting and hybridisation with feral animals. The species are nationally protected though enforcement is poor. The number of surviving individuals is unknown.
With a declining population numbering fewer than 250 mature individuals fragmented into sub-populations of fewer than 50 individuals in total, the Malabar Large-Spotted Civet is one of the planet’s most endangered mammals. Found in the Western Ghats, India, its favoured habitats of lowland swamps and forests have been completely removed. This forces the species to utilise previously undesirable degraded or secondary habitat and thickets in cashew plantations. Conflict with humans is a severe threat as the species will opportunistically raid for poultry. It does not currently exist within any protected areas.
Sheath-tailed bats are so-called due to the projection of the short tail through the tail membrane which effectively forms a sheath. The species is found on the islands of Silhouette, Mahe and Praslin in the Seychelles. There appears to have been several precipitous population declines; in the late 1800′s – 1900′s during the clearing of lowland forests and again since the 1970′s when the species was apparently common. It is now thought that there are fewer than 100 mature individuals remaining. Habitat loss for invertebrate prey, loss of roost sites and predation by introduced species are evident threats.
This sub-species exhibits a limited distribution in northwest Africa, specifically Algeria, Niger, Benin and Burkina Faso. Though very little is known about the species, it probably mirrors the ecology and life histories of other A. jubatus subspecies. There exists no sub-population of more than 50 mature individuals; the total number of mature individuals is thought to be fewer than 250 animals.
The Giant Sable is endemic to Angola where it inhabits the area between the Kwango and Luando rivers. This secretive species cuts a striking figure due to their large curved horns which are present in both sexes (though male horns are longer and more curved). They exhibit a preference for forest and associated riparian habitats where they a specific and preferential browsers. The population has declined and fragmented largely due to long-term military conflict and hunting; only 200-400 individuals remain. It is possible that a viable population (>50 individuals) exists within Luando Strict Reserve. Hybridisation with Roan antelope (H. equinus) is a current threat.
This species was thought to be extinct until an extant population was discovered. No specimens have been recorded since 1937 when the species was restricted to Zapata Swamp, Cuba. Introduced rats and mongooses and habitat destruction may have resulted in the extinction of the species some time ago. However, reports of tracks and droppings suggest that a small population may persist.
The brush-tailed bettong (or, to give it its Australian moniker, Woylie) belongs to the marsupial family Macropodidae which also includes kangaroos, wallabies and the like. Though it was once more widespread and could be found in a variety of habitats, it is now restricted to dry forest understory around Alice Springs, Western Australia. Despite conservation efforts, the species has continued to decline with some small populations disappearing altogether. There are translocated populations in Western Australia, New South Wales and South Australian islands which exhibit varying degrees of success.
The Yellow-tailed Woolly Monkey can be found in montane and cloud forest habitats of San Martin and Amazons in the Peruvian Andes. Originally described from a skin in the early 1800′s, it was re-discovered in 1974 (and anyone wishing to delve into this species’ history should note that it was reassigned from the genus Lagothrix to Oreonax in the early 2000′s). Since this time, the species has suffered a significant population decline as its previously inaccessible habitat was opened up by colonisation projects, road building, logging and other such projects. Habitat loss is a continued threat as is subsistence hunting by natives. Current population numbers are unknown.
This extremely rare and elusive species is endemic to the 284km2 Japanese island of Iriomote, 200km off the coast of Taiwan. Despite the largely mountainous evergreen nature of the island, the cat apparently favours lowland wetland, streams and small hills. Loss of this lowland habitat over the course of the last decade may have resulted in population decline. There are fewer than 100 individuals remaining though the population is contiguous.
B. pygmaeus is thought to have diverged from the mainland brown-throated sloth (B. variegatus) lineage when the island of Escudo de Veraguas split from the Panamanian mainland c. 8900 years ago. The species seems to exist on nutritionally poor red mangrove leaves. Its island home is less than 5km2; what little habitat it supports is declining is quality. There is no information available on its population status.
The Riverine rabbit, probably the most endangered lagomorph in the world, is endemic to the Karoo region of South Africa. Its population has been severely fragmented due to anthropogenic impacts on the landscape. These factors have also served to isolate the remaining sub-populations, limiting or omitting effective gene flow. Though the rate of habitat loss has been arrested, hunting and accidental snaring does occur and the remaining population may become extinct within 50 years without intervention. There are fewer than 250 breeding pairs remaining.
New Zealand. The species was first described in 1886 but was not collected from Dent Island until 1975. In 1990, the breeding population was estimated at 60-100 birds, which declined further to 25 pairs in 1998. The species has been successfully introduced to Codfish and Campbell Islands. The total population is now estimated to be around 200 birds, though this includes captive specimens. Alien species, severe weather and avian diseases are primary threats.
endemic to Ecuador where it inhabits the north-western slopes of the Volcan Pichincha and the Cordillera de Toisan. The Pinchincha population numbers approximately 160 individuals and is restricted to an area of around 34km2. The total wild population has been estimated at between 250 and 999 individuals. Deforestation and habitat destruction is the greatest cause of past decline and the greatest ongoing threat to the species.
where it likely exists as a tiny and spatially restricted population. Little is known of the species, even amongst local people. It is thought that it exploits a more terrestrial lifestyle than that of other Aegotheles species. Based on a similar species – A. cristatus – it is thought that introduced predators and habitat loss are primary threats.
The Bengal florican is a bustard – the Family Otididae which includes the heaviest flying bird, the great bustard (Otis tarda) – which occurs in two populations; one in India, through Nepal, the other in southeast Asia. These populations fragmented into small sub-populations. The total global population is thought to be between 250 and 999 individuals. There have been no recent surveys of the Indian population. The primary threat is loss of key grassland habitat.
saw its population decimated in three generations. The remaining wild population – estimated at around 250-300 individuals – is found in Llanos de Mojos, Bolivia. Drastic reduction of the trade in wild-caught birds has halted the decline and there are signs of recovery. Other threats are hunting for feathers and meat, inter-specific competition and inbreeding of fragmented sub-populations.
(Furnariidae), a family famous for the horneros (Furnarius spp.) which build oven-like clay nests. The Rayadito is more demure, nesting in natural cavities. It is found only on the island of Alejandro Selkirk in the Juan Fernandez Islands, Chile. Recent surveys put the population at c. 248 birds though based on availability of suitable habitat, the total population may number as many as 1,000. Primary threats are habitat loss, climate change and an increase in red-backed hawks (Buteo polysoma exsul).
of the larger olive ibis (Bostrychia olivacea). It is endemic to São Tomé, São Tomé e Príncipe where it inhabits catchments in the south-west and centre of the island. Threatened by habitat loss and intense hunting pressure, the population has dwindled to fewer than 50 birds.
patches of forest to the north of the island of Reunion in the Indian Ocean. One of these sub-populations now consists of fewer than 25 individuals. From 2003 to 2007, numbers of unpaired males increased by over 10% every year, indicative of a heavy male skew in the population. Predation by rats, disturbance, invasive plants and inter-specific competition continue to contribute to the decline of the species. Fewer than 25 breeding pairs remained as of 2007.
woodpecker was thought extinct for several decades. However, a male was caught in a mist net in 2006; several specimens have been recorded since. It is known from several states where it is thought to be associated with bamboo and babassu palm forest. The current population is cautiously estimated at 50-250 individuals. Due to the number of captures and the likely size of its range, however, it is likely that the population is large and the species may soon be downlisted.
name of this species is a misnomer. Rather than being a true hawk (Accipiter spp.), Ridgeway’s is in fact a buzzard (Buteo spp.). Once recorded from Haiti and many associated islands, the species is now likely restricted to Los Haitises National Park in the Dominican Republic. The species is undergoing an annual decline of c. 5-10% of breeding pairs at one site which also experiences 10-15% annual forest loss. There were estimated to be between 80 and 120 breeding pairs as of 2006. A translocation effort by the Peregrine Fund is ongoing.
efforts since 1981 when the population was just 23 individuals. Despite contstant effort, the species remains one of the rarest shorebirds in the world. The wild population has almost certainly been saved from extinction by the annual release of large numbers of captive-bred birds. Once widespread across North and South islands of New Zealand, breeding is now restricted to the Waitaki Valley on South Island. The total population stood at 78 birds as of 2007-08, 20 of which were breeding pairs. Predators, nest-site disturbance and stochastic weather events are the primary threats.
Norfolk Island where the remnant population is confined to Norfolk Island National Park. Despite occasional reported sightings, official surveys have been unable to find a single individual. If the species persists, it does so in low numbers. It is threatened by rat predation and the destruction and alteration of suitable habitat.
along the island chain which includes Papua New Guinea and the Solomon Islands. The extent of its breeding range or area of occupancy whilst at sea are unknown. The global population is thought to be larger than originally estimated due to the sighting of around 160 birds between New Britain and New Ireland in 2008. The species may be threatened at its breeding grounds by invasive predators.
Raso (7km2) in the Cape Verde Islands. The species’ population appears to fluctuate in response to climactic conditions with recorded numbers veering from a low of 20-50 pairs to around 250 individuals. The species is especially vulnerable during periods of low abundance as the sex ratio becomes skewed 3:1 towards males. Primary threats are grought and nest predation.
The Chinese alligator is an inhabitant of the lower reaches of that much abused water-course, the Yangtze river (Anhui, Jiangsu and Zhejiang Provinces), which is home to a number of endangered taxa and was home to the recently-declared-extinct Yangtze river dolphin (Lipotes vexillifer), or ‘Baiji’. While generally amphibious in habits, A. sinensis is dependent on terrestrial nesting, basking and burrowing sites. The wild population is fragmented over a small area of occurrence. There are approximately 200 adults remaining.
Previously common across much of southern Asia, the Siamese crocodile has been extirpated from the majority of its former range. Indeed, it is possible that the species is no longer present in many areas which it is currently believed to inhabit. Current population levels are unknown; the species is threatened by habitat destruction, hunting and persecution.
The species which comprise the genus Abronia are collectively and commonly known as alligator lizards due to their wedge-shaped heads and pseudo-crocodilian morphology. A. montecristoi is native to El Salvador and Honduras where it typically inhabits cloud forests. Like many inhabitants of such ecosystems, A. montecristoi is threatened by habitat loss and climate change. Little is known of the species ecology or population levels.
B. taeniabronchum is a little-known inhabitant of South African montane fynbos (Western Cape natural shrub/heathland). First described in 1831, the species is adept at avoiding detection due to its facility for impromptu crypsis and small size (<20cm). Little is known about the species ecology or population size.
L. cursor is a colubrid species restricted to the 0.2km2 Caribbean island of Rocher du Diamant. Like other Liophis species, L. cursor is entirely terrestrial, hunting its prey in moist habitats. Until recently, the species could be found on the island of Martinique. However, since the introduction of the small Asian mongoose (Herpestes auropunctatus), L. cursor populations on Martinique have suffered dramatic declines and the species is probably no longer present.
P. antanosy is a small gecko (~10cm) which inhabits two small, low-altitude coastal forests in the Tolagnaro region of Madagascar. The two populations are split into several sub-populations which inhabit bounded by forest fragments. One inhabited forest fragment in Sainte Luce will almost certainly be lost to an ilmenite mine. While the species may be relatively common in these forests (this is purely hypothetical), their restricted distribution (~9km2), a decline in habitat quality and habitat destruction. It is especially susceptible due to its reliance on two species of tree, both of which are heavily exploited resources.
This large-bodied iguana was once common across Puerto Rico but is now predominantly restricted to Anegada Island, the Virgin Islands. Between 1968 and 1991, its population density fell from 2.03/ha to 0.36/ha; based on recent surveys and estimates, there are only 164 individuals remaining on Anegada. Two founder populations have been established on associated islands (Necker and Guana) but even taking these populations into account, the total number of individuals is approximately 200. The species is threatened by habitat alteration by introduced grazers and predation by introduced carnivores.
This particularly large wall lizard grows up to 60cm in length (a large proportion of which is tail) and is found on the island of El Hierro in the Canary Islands. Once relatively abundant, predation by introduced species and over-collection resulted in population declines and fragmentation. The declines had halted by the time of the last report (2008) but control of feral cats ceased in 2002 which may result in resumed declines. Several populations have been reintroduced to neighbouring islands. Nevertheless, only 300 – 400 individuals remain.
P. longirostris is the only terrestrial vertebrate endemic to the archipelago of Bermuda. Habitat loss to agriculture and residential developments has resulted in the decline of this once common species. The impacts of habitat development are exacerbated by invasive species and pollution. Though the species currently inhabits several islands, Southampton Island is believed to be home to the only viable sub-population (~400 animals).
This arboreal pitviper is native to the island of Ilha da Queimada Grande, Brazil; an area of less than 0.5km2. While the population is currently stable, the limited area of occurrence and declining fertility amongst the population ensure its place on the Red List.
There is little information available on this Bolivar State (Colombia) native. It is known to inhabit forest ponds and brooks where it feeds on molluscs, insects, fish and amphibians. Habitat loss is likely to be the primary threat.
While this species can be found in Malaysia, Indonesia, Bangladesh and India, the fragmented and declining nature of the small sub-populations put it at very real risk of extinction. Threatened on many fronts – overexploitation of adults and eggs, habitat loss, accidental trapping and netting, pollution, siltation, etc. – it is no surprise that populations have plummeted in the last 25 years. The species is sporadically protected across its range.
This species, endemic to Myanmar, is readily identified by the beautiful pattern of yellow lines radiating from central points on its black carapace. This is actually an inverted perception of the true colouration as the lines reflect the colour of the carapace which is covered by dark patterning. While a popular and much sought-after pet, little is known of its wild ecology. Over-collection for the Asian food and medicine market and the international pet trade has resulted in a dramatic decline in numbers. The species – possibly the most endangered tortoise – currently exists in three areas in the wild, two of which are protected areas.
criteria when assessing species abundance. The primary criteria include population size, geographic range and the projected population size over a given period. In order to full quantify their assessment, the organisation also takes other factors such as habitat quality, exploitation, pollution, competitive species, hybridisation and introduced species into account. This approach is designed to incorporate as many parameters and influencing factors as possible so that accurate assessments can be made. It is so highly regarded that several countries including Canada, Mexico and Australia use IUCN criteria as a basis for their national strategies when assigning conservation priorities to rare or endangered species.
status according to three parameters: population size (somewhere large and everywhere small), geographic range (wide and narrow) and habitat specificity (broad and restricted). There are of course limitations inherent in this system, not least the suggestion that applying these criteria is a subjective and context-dependent endeavour. but it appears to be broadly effective nonetheless. It is worth noting that several studies, each surveying disparate taxa, have been unable to classify any organisms in the category of narrow distribution, broad habitat specificity and small population size.
This nocturnal toad inhabits limestone outcrops in Puerto Rico. The species common name is derived from the prominent crests which can be seen above the eyes and towards the tip of the snout. As they breed in seasonal pools, habitat destruction is a severe threat, as are introduced species such as the cane toad (Bufo marinus) which may oust P. Lemur from suitable habitat. There may be as few as 250 mature individuals remaining. 
First described in 1976, L. lorica has been described from four sites in north-east Queensland, Australia. It has been estimated that there are less than 50 mature individuals remaining. Though the species has not been described since 1994, its rainforest habitat has been protected since 1988. A relocation program was undertaken in 2008. The continued decline of this fast-flowing stream specialist may be attributable to disease such as chytridiomycosis.
L. archeyi can be found in the western Whareorino range and eastern Coromandel ranges of Waikato Region, New Zealand; the two sub-populations are geographically isolated. Previously abundant (<1996), the species has experienced an overall population decline of over 80% in the past decade. The most likely threats are predation by introduced mammals and the effects of the chytrid fungus.
, this species is restricted to a range of less than 100km2 in Lubuk Selasi, Sumatra, Indonesia. Despite have a limited distribution, it is apparently fairly abundant therein. Repeated surveys have failed to find specimens elsewhere on the island. Habitat destruction and stream siltation are the primary threats.
The Baw Baw frog takes its name from the 80km2 plateau it inhabits and which lies some 120km from Melbourne, Australia. There has been a marked decline the number of adult males in the population, though no specific cause has been identified. The plateau has been invaded by several alien species; climate change, UV radiation, pollution and disease have been implicated in the declines of other similarly located species (though no such study has been undertaken in Australia).
P. cerigensis is a narrow endemic species restricted to Karpathos Island, Greece. Previously abundant (~1960s), the species has been found in one location; an area of less than 10km2. It is thought that numbers are declining in response to habitat loss and degradation.
H. rosei is endemic to Table Mountain, South Africa, where it inhabits an area of approximately 9km2. Though adults have been observed in travelling across land, the species is nevertheless restricted to the protected land which describes its known range. The primary threat to this species is habitat alteration due to the presence of invasive flora riparian flora.
Xenopus species are unique in exhibiting dodecaploidy. X. longipes was first described in 1991; little of the species ecology is currently known. It is only found in Lake Oku, a 10km2 waterbody in central Cameroon. Though the frog is currently abundant within the lake, the introduction of fish by locals for food would likely result in a swift decline.
This splendid newt is native to a single catchment in Luristan Province, Iran. Due to seasonal extremes, the species aestivates during the summer and breeding during the winter rains. Somewhat unsurprisingly, there is great demand for this species from the international pet trade. Over-collection and habitat loss have driven the rapid fragmentation and decline of the population. It is thought that fewer than 1000 mature individuals inhabit a range of less than 100km2.
A. andersoni is known only from Zacapa Lake and associated tributaries, Michoacan, Mexico. It is a paedomorph, retaining juvenile characteristics when sexually mature (neoteny). The species exists within a range of less than 100km2. Primary threats are overexploitation for food and recently introduced predatory fish.
This species is only known from the Shir-Abad cave and its associated stream 60km east of Gorgan, Iran. Approximately 100 adults are remaining, all of which live within the described range (<10km2). Habitat degradation due to people visiting the cave is the greatest threat to the species.
This long-lived, slow-growing salamander (the common name is misleading) is endemic to Beilun, Zhejiang Province, China where the two remaining sub-populations (one having been extirpated recently) are found within a range of less than 100km2. Their life history leaves the species vulnerable as they do not achieve maturity until their tenth year. The deleterious impacts of habitat destruction, pollution, human encroachment and collection for scientific collections pose the greatest threats. The individual in the photograph is exhibiting the anti-predator posture known as the unken reflex.
There is little information [immediately] available regarding this species. It is found at an altitude of between 2,500 and 3000m above sea level on the Sierra de Juarez, north-western Oaxaca, Mexico. The last record of the species dates from 1999; it may already be extinct in the described locality. Reasons for this decline are unknown; some negative anthropogenic impacts are likely though habitat quality rules these out as primary factors.
B. niedeni is found only on Sagalla Hill, Kenya where it has a known range of less than 100km2. The type locality is isolated from similar habitat and is declining in quality. Where present, B. niedeni is considered to be quite common. Specific threats are not known, though increased flooding, destruction of montane forest habitat and increased pesticide use may have negative effects.
