Little Swan Island hutia

Survival under extreme conditions

As early as 1942, the American zoologist Glover Morrill Allen warned in Extinct and Vanishing Mammals of the Western Hemisphere about the threats that could endanger the survival of the Little Swan Island hutia, which occurred only on Little Swan Island:

“At present the species seems safe enough within the narrow confines of its island home, but should important changes take place there, such as clear-cutting or the introduction of goats or mongooses, its future would be immediately endangered.”

Extinct and Vanishing Mammals of the Western Hemisphere. 1942. p. 110f. G. M. Allen

These prophetic words came true more quickly than Allen probably expected, because less than 20 years later the Swan Island hutia was extinct. Little Swan Island in the Caribbean Sea, only 2.4 kilometers long and half a kilometer wide, was certainly a secluded home for the hutia, but life in isolation also entails great dangers. On the one hand, the islet offered protection from external threats, but on the other it made the animals vulnerable to invasive species and environmental change—factors that can quickly decimate a small population in such a limited space.

The story of the Swan Island hutia begins in 1887, when the American zoologist Charles Haskins Townsend traveled with the research vessel USS Albatross as a member of the United States Fish Commission to the Swan Islands in the Caribbean Sea. Townsend, who was actually tasked with deep-sea research, discovered a previously unknown rodent on Little Swan Island and captured two type specimens of this species, which is now known as the Swan Island hutia or Little Swan Island hutia.

Percy R. Lowe, a British naturalist, visited the Swan Islands in 1908 and described the peculiarities of these unusual animals a few years later in his book A Naturalist on Desert Islands:

“This rat has an extremely mild and almost friendly disposition, a head and body strongly resembling those of a gigantic guinea pig, and is covered with rather long and silky hairs standing out through a dense coat.”

A Naturalist on Desert Islands. 1911. p. 112. P. R. Lowe

Besides its peaceful nature and striking appearance, the Little Swan Island hutia, which moved around rather slowly, was distinguished by its adaptation to the barren conditions on the flat coral island, which offered neither fresh water nor great plant diversity. The hutias or short-tailed hutias had no choice but to feed on the few shrubs and thorn bushes that grew on the rocky limestone island.

But the introduction of domestic cats by humans and a devastating hurricane in 1955 upset the fragile balance on Little Swan Island, causing the rapid decline of the small population. Allen’s warning words were ultimately confirmed: human interference and the hurricane put the island’s flora and fauna at risk—and the Little Swan Island hutia, which was actually perfectly adapted to survival in the secluded island world with its warm tropical climate, vanished forever.

Little Swan Island hutia – fact sheet

alternative name	Swan Island hutia
scientific names	Geocapromys thoracatus, Capromys thoracatus, Geocapromys brownii thoracatus, Capromys brachyurus thoracatus, Geocapromys thoractus
original range	Little Swan Island (Swan Islands, Caribbean)
time of extinction	probably between 1955 and 1959
causes of extinction	cats introduced to the island, hurricane
IUCN status	extinct

On the range of the Little Swan Island hutia

Townsend discovered the Swan Island hutia “on Little Swan Island, one of two small islands at the entrance to the Gulf of Honduras,” according to the original description from 1888. This remote island of uplifted coral limestone in the northwestern Caribbean Sea, only about two square kilometers in size, represented the only known range of the Little Swan Island hutia. Although the larger Great Swan Island lies only about 500 meters away, there is no evidence that the species also occurred there.

The plateau that forms the top of Little Swan Island is covered with dense vegetation of low trees, thorn scrub, and cacti, forming a flat canopy over the rugged and heavily eroded limestone surface.

The Swan Islands (Islas del Cisne) belong to the West Indies; the nearest mainland, Honduras, lies about 180 kilometers away. The island group also includes the tiny Booby Cay, or Third Cay, which is little more than a rock or sandbank in the water. Compared with the two larger islands, Booby Cay has neither significant vegetation nor a stable animal population.

How did the Swan Island hutia reach Little Swan Island?

Geological studies described by Gary S. Morgan in his article Geocapromys thoracatus (1989) suggest that the Swan Islands have been isolated at least since the Miocene and may only have formed in the Pleistocene—in other words, they were never connected to the mainland. But how could the Swan Island hutia have reached this remote habitat? Oceanic islands that never had a land connection are typically poor in land mammals, because they are difficult for them to reach—the West Indies are an exception. Percy R. Lowe, who visited several islands of the Caribbean in 1908, including the Swan Islands, also asked himself this question.

“How these rats found their way to Swan Island is a small aspect of the problem of the distribution of species that may be worth mentioning. For, as we have seen, there is every reason to assume that Swan Island was never connected with the mainland and, geologically speaking, arose much later than the islands of the Greater Antilles, since it is a relatively recent coral formation. In fact, one might regard Swan Island, in respect of its fauna, as an oceanic or pseudo-oceanic island.”

A Naturalist on Desert Islands. 1911. p. 113. P. R. Lowe

I. Island hopping

To clarify this question, scientists have developed several theories over time. One of them comes from the American paleontologist and zoologist Gary S. Morgan (1985, 1989): during the Pleistocene ice ages, parts of the Nicaragua Rise—a submarine plateau in the western Caribbean Sea—may temporarily have stood above sea level. This could have allowed the Little Swan Island hutia or its ancestors to reach Little Swan Island by island hopping from Jamaica.

The assumption that the ancestors of the Swan Island hutia came from Jamaica and descended from the Jamaican hutia (Geocapromys brownii) is based on morphological similarities. Through long isolation on Little Swan Island, the Jamaican hutias may have evolved independently over thousands of years and eventually differentiated into a distinct species, the Little Swan Island hutia.

II. Overseas dispersal

An alternative theory for the colonization of Little Swan Island by the Swan Island hutia was formulated by the British naturalist Percy R. Lowe:

“For those who have never concerned themselves with such a subject, it should be noted that such a journey across the open sea was only possible if the rats were carried out to sea on a floating island of vegetation or a mass of interwoven tree trunks such as are often seen in mangrove swamps.”

A Naturalist on Desert Islands. 1911. p. 114. P. R. Lowe

This scenario describes “passive drift” or a rafting event in which animals travel long distances across the open sea on drifting vegetation. Such events are random and rare, but they play an important role in the colonization of remote islands.

In A Contribution to the Zoogeography of the West Indies (1914), the American herpetologist Thomas Barbour expressed criticism of this theory. He considered it “mathematically improbable” that a hutia could reach Little Swan Island on an island of vegetation, since Jamaica has no rivers capable of driving such islands out to sea. In addition, the probability that an island of vegetation would accidentally contain a hutia and be steered precisely enough to reach the small island is extremely low. A stable population would also require at least two animals arriving within a short period of time.

In contrast, Gary S. Morgan and Charles A. Woods argue in Extinction and the Zoogeography of West Indian Land Mammals (1986) that non-flying mammals may have colonized the West Indies by overseas dispersal. Because the Caribbean islands had already assumed their present position in the Miocene and were never connected to the mainland, the crossing of water remained the most important route of colonization for mammals from South America to settle distant islands.

For the geologically relatively young Swan Islands, including Little Swan Island, Morgan and Woods consider passive drift the most likely method of colonization. The Swan Island hutia may therefore have reached Little Swan Island from a neighboring island such as Jamaica with the aid of a drifting island of vegetation, where it then evolved in isolation into a distinct species.

III. Active dispersal by early settlers

A third theory assumes that humans may have deliberately brought the ancestors of the Little Swan Island hutia to Little Swan Island. Garret C. Clough suggests in an article on the Bahama hutia (1972) that the first human settlers moved eastward about 7000 years ago from Honduras across the central Caribbean island chain, including Little Swan Island. In this scenario, hutias from Central or South America could have been transported on rafts with the settlers.

The hypothesis that people from Jamaica brought the ancestors of the Little Swan Island hutia—that is, the Jamaican hutia—to Little Swan Island centuries ago is doubted by Morgan in Taxonomic Status and Relationships of the Swan Island Hutia (1985). He argues that morphological peculiarities, that is specific physical and anatomical features, indicate that the Swan Island hutia has been isolated on Little Swan Island since the late Pleistocene or even longer. A comparatively late introduction by humans is therefore unlikely. Morgan thus supports the assumption that the Swan Island hutia reached the island naturally, for example by overseas dispersal, many thousands of years ago.

Causes of extinction: Cats and hurricanes

When Lowe visited Little Swan Island in 1908, he described the island, which could safely be reached from Great Swan Island only on calm days, as completely secluded and untouched:

“The only thing that could possibly stimulate any sort of commercial enterprise on the island—a phosphate deposit at its eastern end—was never exploited.”

A Naturalist on Desert Islands. 1911. p. 105. P. R. Lowe

Lowe added that the Little Swan Island hutia on Little Swan Island could live “completely undisturbed and without enemies—neither human nor otherwise.” Little Swan Island, difficult to reach and rocky, was always uninhabited because of its sparse vegetation and lack of fresh water, so human interference can be almost ruled out. Hunting or trapping the Swan Island hutia also probably served mainly scientific interests and was likely limited to the documented visits to the island.

A hurricane and introduced cats

Both the IUCN and Morgan (1985) attribute the extinction of the Swan Island hutia to two decisive factors: the devastating Hurricane Janet in 1955 and the introduction of domestic cats to the island. According to Clough’s contribution Current Status of Two Endangered Caribbean Rodents (1976), a box of unwanted cats was released on Little Swan Island before 1960. The combination of the effects of the hurricane, which probably damaged the vegetation and thus the food base, and the invasive cats, which posed a direct threat to the ground-dwelling, slow rodents, ultimately led to the extinction of the species.

Cats were able to hunt the Little Swan Island hutia without great difficulty. In addition, there were no natural enemies on the island that could have limited the cat population, so the predators multiplied rapidly and increased the hunting pressure on the already small hutia population. The island originally harbored only reptiles, crabs, and birds—no other mammals.

That Little Swan Island hutias would have been easy prey for cats is illustrated by a report from Lowe. He describes that a specimen he brought to Great Britain showed no fear whatsoever of predators:

“I had the honor one day of showing it not only to His late Majesty King Edward VII, but also to his favorite dog ‘Caesar.’ In the dog’s presence the rat showed not the slightest sign of fear or distrust, nor any reverence for His Majesty. (…) While the dog was cautiously held back, the rat came to the edge of the low table on which it sat and calmly inspected, only an inch or two from the dog, what must have been for it a most extraordinary and surprising apparition.”

A Naturalist on Desert Islands. 1911. p. 114f. P. R. Lowe

Swan Island hutias also seem to have had no fear of humans at all, because Lowe continued:

“On the homeward voyage, and indeed almost from the first moment of their arrival on board the yacht, both rats felt entirely at home and became favorite pets with the sailors. They were allowed to run about on deck and crawled over anyone who happened to be lying there, without showing the slightest hint of danger or fear.”

A Naturalist on Desert Islands. 1911. p. 115. P. R. Lowe

This ecological naivety, which makes species particularly vulnerable, is typical of island-dwelling animals that have lived isolated for a long time without natural enemies such as predators or humans.

Goats on Little Swan Island?

Morgan wrote in 1989 that a few years before the hurricane and the arrival of the cats, goats had been introduced on Little Swan Island and had thus also contributed to the extinction of the Swan Island hutia. This is probably an error based on a remark by Lord Moyne from the book Atlantic Circle (1938). Lord Moyne, a British-Irish politician and brewery owner who monitored the condition of British colonies in the 1930s and stayed, among other places, in the British West Indies, wrote about his stay on Little Swan Island in 1937:

“Only a few weeks earlier the foreman on the western island had introduced six goats, and if these animals multiply, the destruction of the flora and fauna is only a matter of time.”

Atlantic Circle. 1938. p. 86. Lord Moyne

Moyne was most probably referring to Great Swan Island, because the Swan Islands consist of two main islands: Great Swan Island in the west and Little Swan Island in the east. In the 1930s, Great Swan Island was temporarily inhabited and served, among other things, as the site of a weather station, which makes the introduction of goats there more likely.

The tragic story of the Swan Islands hutia is unfortunately no isolated case among island species. The Lyall’s wren, a small flightless songbird, would probably also not have become extinct had cats not been introduced to the small rocky island of Stephens Island, which belongs to New Zealand.

When did the Swan Island hutia become extinct?

Naturalists of the early 20th century described the Little Swan Island hutia as abundant on Little Swan Island into the 1930s, perhaps even into the early 1950s. Lowe, for example, writes that in 1908 several animals could be collected without difficulty:

“The first Swan Island rat that we saw was in the hands of Mr. Eagle, the first officer, who had just shot it. (…) The second rat ran over some rocks in front of us and tried to hide beneath the spreading roots of a large undermined tree. This I caught (…) by the hind leg and gently drew out (…). We saw at least a dozen others running about and taking refuge in the great fissures with which the island is traversed. We collected several more specimens and caught yet another alive.”

A Naturalist on Desert Islands. 1911. p. 114. P. R. Lowe

The American zoologist, botanist, and photographer George Nelson was also on Little Swan Island in March and April 1912 and caught 15 animals within a short time, according to Morgan (1985). Nelson worked as a preparator at the Museum of Comparative Zoology at Harvard University in Cambridge, Massachusetts, USA. In this function he collected and prepared natural specimens and animals for the museum collection, including specimens of the Swan Island hutia.

The last known naturalist to observe the Little Swan Island hutia in large numbers was probably Lord Moyne in 1937. In Atlantic Circle he reports such a great number of hutias that “four men from the western island caught about twelve animals for us alive without nets or traps—in about two hours.”

Unsuccessful searches for the Little Swan Island hutia

From February to April 1960, the marine scientist Harris B. Stewart Jr. undertook an expedition with the vessel USC & GS Ship Explorer during which he and his colleagues searched Little Swan Island for traces of the Little Swan Island hutia. According to the Oceanic Cruise Report (1962), however, no animals could be sighted; even the droppings that were said to have been ubiquitous ten years earlier had disappeared.

Additional searches took place in the 1970s: the herpetologists Ronald Crombie and Stephen Busack spent two days on the island in February 1974 collecting reptiles for the Smithsonian Institute, but saw neither hutias nor their traces. Clough (1976) and Robert Howe also searched Little Swan Island in July and August 1974 for five days specifically for Swan Islands hutias or signs of their existence. The only indication of their former existence was a weathered skull; otherwise they found neither animals nor fecal pellets.

According to Morgan (1985), the Swan Island hutia has not been seen alive since at least the early 1950s. Since it was still obviously abundant in 1937 and was no longer documented from 1960 onward, it must have declined rapidly to extinction in the 1950s. The extinction period can be narrowed down to 1955 to 1959, because during this interval both the hurricane passed over the island and invasive cats were released on Little Swan Island. The International Union for Conservation of Nature (IUCN) officially placed the Swan Island hutia on the list of extinct species in 1982.

In 2012, the ecologists Diana O. Fisher and Simone P. Blomberg of the University of Queensland calculated in a study the probability of rediscovering supposedly extinct species. They set the year of the last sighting of the Little Swan Island hutia to 1955, the year Hurricane Janet devastated the island, and estimated the mean extinction date as 1972. Because of the long absence and the threat factors, the applied model indicates an extremely low probability that the Swan Island hutia will ever be rediscovered.

Caribbean: At least 29 terrestrial mammals have gone extinct since 1500

Why are or were there so many endemic land mammals on the Caribbean islands compared with other island groups worldwide? Islands such as New Zealand, or smaller islands such as Stewart Island and Stephens Island, had practically no native land mammals before the arrival of humans except bats. Instead, the fauna there was dominated by birds. The reason lies in the enormous isolation of these islands: New Zealand is about 2,000 kilometers from the Australian mainland. This distance made it impossible for land mammals to reach New Zealand naturally.

The Caribbean islands, including the Swan Islands, are considered a biodiversity hotspot and belong to the few oceanic island groups inhabited by non-flying land mammals. Samuel T. Turvey emphasized in a 2017 article in the Journal of Mammalogy that this region simultaneously has the highest number of extinct mammal species in the world: since 1500, that is since the beginning of the colonial period, at least 29 mammal species have disappeared. Only two endemic land mammal families still exist in the Caribbean today, chiefly on Cuba, Jamaica, and the Bahamas: the hutias (Capromyidae) and the solenodons (Solenodontidae).

For the last 4,500 years, that is since the arrival of humans on the West Indian islands, Morgan and Woods (1986) document a total of 37 extinct non-flying mammals in the Caribbean. Examples of extinct mammals include the Jamaican monkey, which disappeared in the 18th century, as well as the Hispaniolan edible rat and the insular cave rat, both of which became extinct already in the early 16th century. In addition, all species of Caribbean shrews (Nesophontidae) became extinct by the 20th century at the latest, as did all species of giant hutias (Heptaxodontidae).

The IUCN Red List currently lists 16 hutia species in the genera Plagiodontia, Capromys, Geocapromys, Hexolobodon, Isolobodon, Mesocapromys, and Mysateles. Of these, four are considered threatened with extinction, and six are already extinct. Many of the remaining species show declining population trends due to hunting, habitat loss, and invasive species.

A study published in 2017 by the paleontologist Siobhán B. Cooke analyzes the causes of extinction of mammals on the Caribbean islands and shows that these animal species have been exposed to an extreme risk of extinction in recent centuries. Many surviving species now exist only in very limited areas or are considered highly endangered. Hutias evolved in the isolation of the Caribbean into a multitude of specialized species. But precisely this isolation makes them especially vulnerable to environmental change, because they are trapped on their respective islands.

The main factor in the extinction of many hutia species is the loss of their habitat through deforestation for agriculture and settlements, especially on heavily populated islands such as Jamaica and Cuba. The Swan Island hutia remained exempt from this because hardly any human interventions occurred on its small home island. An additional threat to hutias and other Caribbean mammals was the introduction of predators such as cats, dogs, and especially mongooses. Mongooses were brought to the region in the 19th century to control snake and rodent populations, such as introduced black or Norway rats, but they also attacked hutias and led to sharp population declines.

On the ecology of the Swan Island hutia

Little is known about the way of life of the Little Swan Island hutia. What little knowledge exists is based mainly on the notes of the naturalist Percy R. Lowe, who visited the island in 1908, and of Lord Moyne, who was on Little Swan Island in 1937.

The Little Swan Island hutia most probably fed on the plants that characterized the sparse vegetation of the small coral island. Directly documented observations on the diet of this species are rare: in his 1911 report, Lowe described the hutias as “vegetarian rats” that eagerly accepted “milk as well as every kind of vegetable and fruit” in captivity.

Lord Moyne added in 1938 that the hutias were “gnawing at a kind of wild vine that grew in abundance on the limestone cliffs.” Clough also stated in 1976 that evergreen shrubs such as Strumpfia maritima and Phyllanthus epiphyllanthus, which form the preferred diet of the Bahamian hutia (Geocapromys ingrahami) on East Plana Cay, also occurred on Little Swan Island and therefore probably also formed part of the natural diet of the Swan Island hutia. The animals probably fed on a limited selection of locally available plants, including twigs, bark, and leaves of hardy shrubs.

There are slightly contradictory reports concerning the activity times of the Little Swan Island hutias: Lowe described them as diurnal animals, whereas Moyne claimed that “they apparently do not leave the protective thicket of cacti until late in the day, two or three hours before sunset.” Clough (1976) mentions Captain Glidden, a longtime inhabitant of Great Swan Island, as another source. He reported: “The hutias on Little Swan were active during the day. Fishermen saw them often when they passed by late in the day on the way back and guided their boats along the open cliffs.” Much suggests that the Little Swan Island hutias were probably crepuscular—in contrast to their recent relatives on Jamaica and the Bahamas, which are almost exclusively nocturnal and hide during the day.

Moyne also described the hutias’ habitats on the island: “Since there is no soil on the island and the animals have no possibility of digging burrows, they live in the jagged fissures in the coral rock.” The entire surface of Little Swan Island consists of a rugged limestone structure, so the hutias depended on natural fissures and cavities. In fact, the absence of dug burrows seems to be typical of the genus Geocapromys, because the Jamaican hutia and the Bahama hutia also prefer natural rock niches, small caves, and washouts in limestone.

This specialization on limestone structures may explain why the Swan Island hutia never occurred on neighboring Great Swan Island, only 500 meters away. Morgan (1985) explained that islands such as Great Swan Island and West Plana Cay, which do not offer large exposed limestone areas and fissures, are unsuitable for hutias. The Jamaican hutia is also found chiefly in regions characterized by extensive limestone outcrops, which suggests that this type of habitat is essential for the survival of Geocapromys species.

Swan Island hutias in museums

A manageable number of remains of the Little Swan Island hutia exist worldwide, which is why a find in the Royal Albert Memorial Museum (RAMM) in Exeter, England, which adds two stuffed animals to the hypodigm of the taxon, attracted special attention. Simon Tonge, director of Paignton Zoo in England, reported in 2014 in the Caribbean Journal of Science how the hutias from Little Swan Island came to England.

In the 1930s, researchers brought a total of 14 Little Swan Island hutias to Great Britain, presumably animals that Lord Moyne had caught in 1937. Moyne hoped to establish a breeding colony, and wrote in 1938: “Upon arrival in England, the females were handed over to three of my friends who specialize in breeding rare species.” The animals were housed in London Zoo and in the then Primley Zoo, now Paignton Zoo, where according to the Zootierliste they lived until 1938 or 1939, but without leaving offspring. Two of the animals from Paignton Zoo were handed over to RAMM after their death, where they were rediscovered only in 2013.

In general, keeping Swan Island hutias in human care often failed.None of the animals caught by Moyne survived more than three years—some died from injuries inflicted by conspecifics, others from pneumonia (Morgan, 1989). A nd the two specimens caught by Lowe in 1908 also did not survive long: “Unfortunately one of the rats died on the voyage home, and the other shortly after its arrival in the Zoological Gardens in Regent’s Park.”

Today, the remains of the Swan Island hutia are distributed among several museums that possess skins, skulls, skeletons, and fluid-preserved specimens. Morgan (1989) listed the holdings: the British Museum of Natural History (BMNH) preserves twelve specimens, four of which were transferred from London Zoo in the 1930s and early 1940s. The Museum of Comparative Zoology (MCZ) possesses ten specimens of the original 15 collected by George Nelson, and the U.S. National Museum of Natural History (NMNH) preserves two specimens, including the type specimen.

The American Museum of Natural History (AMNH), the Field Museum (FMNH), and the Yale Peabody Museum (YPM) each hold one or two specimens originating from exchange stocks of the MCZ or BMNH. These museum holdings are supplemented by the two rediscovered specimens in RAMM, donated by Paignton Zoo in 1938 or 1939.

Taxonomy: from subspecies to species, to subspecies to species

After the American biologist Frederick W. True examined two unknown rodents from Little Swan Island caught by Charles Haskins Townsend in 1887, he described the Little Swan Island hutia in the following year as Capromys brachyurus thoracatus. He classified it as a subspecies of the Jamaican hutia (Capromys brachyurus, now Geocapromys brownii), which belongs to the hutia family (Capromyidae). Since True had no comparative specimens of the Jamaican hutia available, he could rely only on the external characteristics of the animals using Philip Henry Gosse’s description in A Naturalist’s Sojourn in Jamaica (1851). A striking characteristic he used for distinction was the characteristic white band of fur across the chest of the Swan Island hutia—hence also the species epithet thoracatus (Greek for “breast”).

The American ornithologist Frank M. Chapman proposed in 1901, in his revision of the genus Capromys, the creation of the new genus Geocapromys and recognized the Swan Island hutia as a distinct species. He found that the Swan Islands and Jamaican hutias differ clearly in coloration, skull features, and body size, especially in the size of the ears.

This classification did not last long, however: the German zoologist Erna Mohr again ranked the Swan Island hutia in 1939 as a subspecies of the Jamaican hutia, based on superficial comparisons of external characteristics. Many later authors adopted Mohr’s classification and listed the Little Swan Island hutia under the name G. brownii thoracatus, including Clough (1976).

Glover M. Allen (1942) stated that the Swan Island hutia is closely related to the Jamaican hutia because of morphological similarities. However, he noted that the hutia from Little Swan Island was smaller and lighter in color, which he attributed to the dry island environment. On dry, sandy, or sparsely vegetated islands, lighter coloration is better suited to camouflage. Lighter fur also reflects more sunlight than darker fur, which helps regulate body temperature.

Differences between hutias and tree rats

The genera Capromys and Geocapromys, also known as tree rats and hutias or short-tailed hutias, are part of the hutia family (Capromyidae). Whereas the tree rats are more arboreal and have a longer tail, the ground-dwelling hutias have shorter tails. The hutias include species such as the Little Swan Island, Jamaican, and Bahamian hutias, adapted to islands with sparse vegetation.

These generic differences concern not only external appearance, but also reflect the different ways of life and adaptation to the geographic and ecological conditions of their respective habitats. The generic name Geocapromys is composed of the Greek word “geo” for “earth” and the name Capromys, the genus of the tree rats. This points to the more ground-dwelling habits of the hutias compared with the more arboreal tree rats.

The only representative of the tree rats, Desmarest’s hutia (Capromys pilorides), also lives partly in trees and is adapted to the diverse habitats of the large island of Cuba. The ground-dwelling hutias, by contrast, are better adapted to small islands with little vegetation. According to Clough (1972), living and fossil species of the genus Geocapromys were found only on the Bahamas, Cuba, Jamaica, and Little Swan Island.

Today, the genus Geocapromys comprises seven described species, of which only two have survived: the Jamaican hutia and the Bahamian hutia, which was once widespread throughout the Bahamas and now occurs only on East Plana Cay. In addition to the Swan Island hutia, three other extinct species are known from fossil deposits on Cuba: G. columbianus, G. megas, and G. pleistocenicus. Another extinct species, the Cayman hutia (G. caymanensis), comes from the Cayman Islands.

Morgan (1989) compared the Little Swan Island hutia with the two other recent hutia species, the Jamaican and Bahama hutias, and found differences in size, coat color, and tail length. The gray-brown Swan Island hutia had larger, almost hairless ears without tufts of hair, and its tail was longer than that of the Jamaican hutia but shorter than that of the Bahama hutia.

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