The Iriomote cat (Prionailurus bengalensis iriomotensis) was proposed as a species in 1967, but following mtDNA analysis in the 1990s it is now accepted as a subspecies of leopard cat. It is found exclusively on the Japanese island of Iriomote. In 2007 the estimated number was 100 to 109 individuals so it was placed in the category of Critically Endangered by International Union for Conservation of Nature (IUCN) in 2008, as the population size is lesser than 250, consists of a single subpopulation and still continues to decline.
In Japanese language it is called Iriomote-yamaneko (Iriomote mountain cat). Local islanders knew about it as yamamaya (the cat in the mountain), yamapikaryaa (that shines on the mountain), and meepisukaryaa (that has flashing eyes). To distinguish between the Iriomote cat and other cats on the island, locals also gave other cats nicknames such as pingimaya (for stray cats) and maya or mayagw? (for house cats). Others, however, believed that they may have just been feral cats.
Iriomote Island, where the cat is found spans about 290 square kilometers. It consists largely of low mountains (300–460 meters) with sub-tropical evergreen forest, including widespread belts of mangrove along the waterways. It is the smallest habitat of any wild cat species in the world. The cat prefers areas near rivers, forest edges, and places with low humidity.
Male of this small wild cat can be 55 to 60 centimeters long and weighs 3.5 to 5 kilograms. Females are smaller in size with about 50 to 55 centimeters length and 3–3.5 kilogram weight. Tail is thick from base to tip and is 23–24 centimeters long. They have long torsos and short, thick limbs. Their necks are thick, and shoulders are muscular, though their jumping power is comparatively weak. Unlike other small cats, their spines cannot bend sharply.
Fur of this cat is mostly dark gray and light brown, with hairs on the stomach and insides of the limbs being lighter. Hairs along the jaw are white. There are two dark brown spots on each cheek. Like the leopard cat, 5 to 7 stripes run from forehead to the back of the head, but unlike leopard cat stripes stop before reaching the shoulders. Dark brown spots cover the sides of the body, and there are 3–4 bands of irregular stripes on the chest. Tail is dark brown; darker spots pattern the back side of the tail while the underside of the tail is solid. The tail-tips are dark.
Ears are round on the tips, with black hair along the edge. There are no tufts of longer hair on the top of the ears. Adult cats have white spot at the back of each ear, like those found on tigers’ ears. However, young of this cat do not have these marks, and even as adults the spots will not be as white as those seen on leopard cats.
Eyes in Iriomote cats are of light amber color. Nose is large and flat, with no fur covering the reddish-brown skin. Skull is longer and narrower than those of house cat. When compared to leopard cat’s skull, it is roughly the same size but thicker. Because of this, Iriomote cat’s brain is smaller—weighs about 30 grams, whereas a male leopard cat’s brain is about 42 grams. An Iriomote cat has a total of 28 teeth, which unlike most other subtropical mammals give details about their year-to-year history. It is expected that these details will help determine age and behavior of the cat. The anal scent glands in these cats surround the anus, which contrasts with other cat species’ which are inside the anus.
Discovery, Classification and genealogy
Iriomote cat was officially discovered in 1965 by Yukio Togawa, an author who specialized on many animals. It was later described in 1967 by Dr. Yoshinori Imaizumi, director of the zoological department of the National Museum of Nature and Science in Tokyo. Dr. Yoshinori announced the presence of this cat to the scientific community as a new species of feline in its own genus. It was named Mayailurus iriomotensis. Dr. Yoshinori pointed out that this cat has retained some especially primitive features compared to other leopard cats. Judging from these characteristics he estimated that the cat appeared as a species sometime between ten million years ago in the Miocene epoch and three million years ago during the Pliocene epoch. According to him they may have shared many primitive characteristics with fossils in the extinct Metailurus genus. The Iriomote cat and Metailurus shared a common ancestor sometime between ten million and five million years ago, and from that he deducted that the Iriomote cat’s ancestors must have widened their range from mainland Asia to Iriomote and other areas beginning three million years ago. To Dr. Yoshinori It appears to be a very ancient species, a ‘missing link’, nearer to the common root of the cat tribe than any other extant species.
In contrast to Yoshinori Imaizumi’s assertions about its unique characteristics, other researchers have strongly refuted the idea that the Iriomote cat is its own species ever since its discovery. On the basis of studies conducted on skulls and teeth, samples and living animals and genetic research Yoshinori’s claim was found to be not sustainable and the animal was placed under the genus Prionailurus as Prionailurus iriomotensis.
Scientists believe that the Iriomote cat diverged from the leopard cat around 180,000-200,000 years ago. According to marine geologists, the Ryukyu Islands were connected to mainland Asia via a land bridge from about 20,000 years ago to 240,000 years ago. It is believed that Iriomote cat moved its range to the islands during this period. Because of this, it is presumed that there is little genetic diversity within the species.
They are nocturnal in nature and are most active during the twilight hours. During daytime, they sleep in caves or the hollows of trees. Their range spreads from 1to 7 square kilometers, and they mark their territory by urinating and defecating on rocks, bushes and tree stumps. They are land mammals, but they do climb trees, go into the water, and even swim.
Like all members of the cat family they too are carnivores preying on various mammals, reptiles, birds, fish, amphibians and crustaceans. They eat about 400 to 600 grams of food daily. While other smaller wild cats, living in various other habitats, primarily hunt small mammals such as rabbits, rats and other rodents, Iriomote cats have wide variety in their food as there is no other carnivore to compete with on the island. Since their hunting grounds tend to be in swamps or on shores, they will sometimes swim and dive to catch water birds, fish, and freshwater prawns.
While feasting on birds that are larger than dusky thrush, most species of cats pluck feathers first and then eat, but Iriomote cats eat even large birds whole without removing feathers. Also unlike other cats, they will not kill their prey right away by breaking the spinal cord. Instead hold the victim in their mouth until it stops moving.
Stool sample analysis of Iriomote cat shows its diet consists of about 60 per cent birds, 30 per cent of black rats, same percentage of insects, 15 to 20 per cent lizards and frogs, 3 to 17 per cent bats and less than 1 per cent boar. Fish and crustaceans appear roughly 3–4 per cent of the time. Seasonal dietary changes have been observed. They have been found eating rats and frogs year-round, lizards in the summer and spring, and crickets and bats more often in fall and winter.
Outside of breeding season these cats are most active during twilight and at night, but in mating season they become active during the day as well. Breeding females are more active than the non-breeding ones during the late night and morning hours. Moreover, outside of the mating season the cats will live in solitary, but when they begin breeding they act together. The mating season lasts from December to March, and females will go into heat several times during this period, with the peak being in January and February. Towards the end of February, they fast for about two weeks and it is during this period the females will be most sexually excited. This is the time when male and females will always be together. It is believed that the conception takes place during these two weeks.
After the mating is successful the female will search out a suitable tree hollow, cavern or crevice and give birth to 1-3 kittens between April and June. Kittens stay with their mother for about eleven months, and they will begin to become more independent during the fall and winter months. They will stay in their mother’s range from anywhere between a few months and years. Kittens attain maturity twenty months after their birth.
Range and territory
Iriomote cat’s range varies seasonally and also individually, however it shrinks during the mating season. These felids are very territorial and will not allow others into their area. Males’ and females’ ranges do overlap and one to two females tend to live within a single male’s sphere. Typically, cats of the same gender will not overlap their territories, but partial overlaps have been observed. These small overlaps are often hunting grounds. According to experts the cats make rounds of their territories lasting three to four days, marking and hunting as they go.
Young males do not have any set territory, so they are always on the lookout for one. When they find one, they immediately grab it. Females will allow their young to stay in their own range and then mark a new territory once the next breeding season comes.
The estimated lifespan of Iriomote cats is seven to eight years in the wild and eight to nine years in captivity. In captivity, a cat named Yon lived for an estimated fifteen years and one month, the longest known lifespan of any Iriomote cat.
Cat under threat
Destruction of habitat to make way for development, accidental deaths, predation by dogs and traps set for wild boar and crabs all have contributed to the decline in number of Iriomote cats. During the second survey of the island, conducted between 1982–1984, it was estimated that 83–108 cats lived on the island. Third survey, conducted from 1993 to 1994, estimated 99–110 cats were on the island. During the fourth survey (2005–2007), there were about 100–109 cats.
IUCN had originally listed Iriomote cat (P. b. iriomotensis) as “endangered”, but an assessment done in 2008 updated its status to “critically endangered” because of its habitat being limited to Iriomote Island and a decrease in numbers.
The cat was designated as a natural monument by the Okinawan government. On May 15, 1972, along with the recovery of Okinawa, it was nationally recognized as a natural monument. On March 15, 1977, it was given special status amongst natural monuments, and in 1994 with the Species Protection Act, it was designated as a Specified National Endangered Species of Wild Fauna and Flora. This act was adopted on January 28 and enacted on March 1.
Prince Philip, Duke of Edinburgh wrote a letter in 1977 to Crown Prince Akihito on the subject of the preservation of Iriomote cat. A report attached with the letter suggested that further migration to the island and the cultivation of land on the island should be banned. Crown Prince Akihito replied saying that he wished for a way that would allow both the preservation of the cat and the continued habitation of the people on the island. He also explained that the prime minister at the time, Takeo Fukuda, was considering of establishing a wildlife sanctuary on Iriomote.
A part of Iriomote’s cat range was designated as Iriomote Ryukyu Government Park on April 18, 1972. With the US’s return of the Ryukyu Islands to Japanese control on May 15, it became Iriomote National Park, and in March of 1991 about 11,580 hectares on the island was designated as the Iriomote Forest and Ecological Preserve in order to protect the natural environment within the area’s confines. Despite these efforts, not enough land within the cats’ preferred habitat of 200 meters below sea level was included. In 1995 the Iriomote Wildlife Preservation Center was established to increase preservation work, enforce research, and to increase the understanding of the cat.
Pets too pose problems
In addition to traffic accidents, logging and development of swamplands, pets too are causing problems for the Iriomote cats. Domestic and stray cats especially cause issues by posing competition, transmitting diseases and genetic pollution due to hybrids born of inter-species breeding. It is also feared that dogs prey on the Iriomote cats.
House cats that have become feral or partially feral pose the greatest threat, but monitoring of these interactions has not been made. Pressures from competition over food, contact with domestic cats that have contracted feline immunodeficiency virus (FIV) and other contagious diseases, as well as decrease in population due to hybridization are all important issues with the Iriomote cat.
The Iriomote Wildlife Protection Center conducted an investigation in June of 1999 among 50 domestic and feral cats and 23 Iriomote cats to find out if FIV was being transmitted within the populations. No Iriomote cat was found having FIV, but three house and feral cats were tested positive. Due to the fear regarding transmission of disease Taketomi Town promulgated the Cat Breeding Ordinance in 2001 which required all residents to get their pet cats registered. In June of 2008, this ordinance was revised and mandatory FIV testing and vaccinations, spaying and neutering, and micro-chipping was included in it. A new limit to the number of pets per owner was also added.
In addition to this cane toad that secretes a poisonous substance from glands in its ears, has also appeared on the island. In order to prevent further contamination of Iriomote, residents of Ishigaki Island began extermination measures in 2008.
In general, names such as yamapikary? are used in reference to the Iriomote cat, but some locals claim to have seen another type of cat on the island. This is described as being twice as large as a domestic cat with a 60 centimeters long tail and a coat pattern, which is different from the Iriomote cat. It has been sighted several times. Locals have given it several nicknames, like kunzumay?, toutouyaa and yamapikary?. It is not thought to be a house cat, stray cat, or an Iriomote cat. Apart from the claims of locals no scientific documentation is available on this mysterious cat.
As a rule, an increase in body size will result in an increase in range for any given species. An Iriomote cat will have a range of 6.5 sq. km; comparing the Iriomote cat’s size to yamapikary?’s, it has been estimated that a yamapikary? would require about 30 sq. km for its range. Iriomote Island is about 290 sq. km, meaning only about ten yamapikary? could live on the island.