Why Do Cats on Japan’s Cat Island Have Stubby Tails?


Cat Island (Tashirojima) is a small island off the coast of Ishinomaki City in northern Japan. It is known for its large population of cats that outnumber human residents. The island is home to a unique breed of cats that have notably short tails. While most cats have long, flexible tails, the cats of Cat Island have tails that are only 4-6 inches long. This distinctive trait sets the island’s feline inhabitants apart from regular domestic cats. The reason behind the truncated tails remains a mystery, though there are several theories. This article will explore the possible explanations for why the cats of Cat Island have developed such unusually short tails over time.

History and Description of Cat Island

Cat Island, also known as Tashirojima, is a small island located in Ishinomaki City off the coast of Miyagi Prefecture in northern Japan (1). Measuring only around 3 kilometers in circumference, Cat Island is part of the Oshika Peninsula and sits among hundreds of tiny islands in the Pacific Ocean. Geographically, the island consists of rocky shores surrounded by cliffs, with a small fishing village nestled in a cove on the northern end of the island.

The remote island has a long history of human habitation dating back to the Edo period in the 17th century when it first became populated (2). Cats were brought to the island as pets and as a form of pest control. The human population grew to over 1,000 residents at its peak in the 1950s, largely dependent on fishing as the main industry. However, as economic decline set in, the younger generation began leaving the island in search of work on mainland Japan. This led to the aging and gradual depopulation of the island, with only around 100 residents remaining today (3).

Meanwhile, the number of cats on the island exploded due to lack of spaying and neutering. Today, the cat population is estimated to be between 120-150, significantly outnumbering the human residents. This abundance of cats led to the island’s nickname as “Cat Island.” The cats hold a special place in the island’s culture and have become one of its main attractions. Tourists come to feed and photograph the friendly felines that roam freely around the village. The island depends on tourism for revenue, capitalizing on its reputation as a cat paradise (1). Although remote, Cat Island has become a famous destination for cat lovers from Japan and abroad.


(1) https://en.wikipedia.org/wiki/Tashirojima

(2) http://www.slate.com/blogs/atlas_obscura/2014/05/15/tashirojima_is_an_island_in_japan_ruled_by_cats.html

(3) https://top.his-usa.com/destination-japan/blog/top_3_cat_islands_in_japan.html

Physical Traits of Cat Island Cats

The cats on Cat Island are known for having short, stubby tails that are only about 4-5 inches long. According to researchers, this is likely due to a genetic mutation that occurred naturally in the island cat population over time (1). The short tails distinguish the Cat Island cats from other domestic cat breeds and their mainland relatives.

In addition to their short tails, Cat Island cats tend to have stocky, muscular bodies. They are medium in size with short legs suited for climbing and hunting in the hilly, rocky terrain of the island. Their fur coats come in a variety of colors and patterns including tabby, calico, tortoiseshell, and solid black or white (2).

There are several hypotheses that have been put forth by biologists regarding the short tails. One is that the stubby tails help the cats better balance and jump between surfaces on the rocky island. Another idea is that the short tails make it harder for birds and other predators to grab the tails of kittens. More research is needed to determine the evolutionary advantage the mutation provided the island cats.

(1) https://en.wikipedia.org/wiki/Tashirojima

(2) https://bigcatrescue.org/iriomote-cat-facts/

Genetic Analysis

Cat Island’s unique population of cats has been extensively studied genetically in recent years. Researchers found that the cats have limited genetic diversity compared to mainland Japanese cats (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10090102/). This is likely due to their isolation on the small island. However, genetic studies provide evidence that the short tails seen in Cat Island cats have a strong genetic basis.

One 2023 study analyzed the full genomes of Cat Island cats and found mutations in genes related to bone and cartilage development that were not present in mainland Japanese cats (https://pubmed.ncbi.nlm.nih.gov/37063514/). The researchers concluded these genetic differences likely lead to abnormal tail development in Cat Island cats, resulting in shortened, kinked tails.

Additional studies are needed to fully understand the genes involved in the unique Cat Island cat tails. But current evidence indicates the trait arose from genetic drift and isolation on the island, rather than environmental factors or human intervention.

Possible Evolutionary Advantages

There are several theories as to how the short tails of Cat Island cats could provide evolutionary advantages.

One is that the shorter tails help with balance and agility in the rocky, cliffy terrain of the island. Cats use their tails to aid in balance and climbing, and a shorter tail may allow the Cat Island cats to maneuver more nimbly over the uneven surfaces (Source).

Another possible advantage is temperature regulation. The Cat Island climate is generally hotter than mainland Japan. The short tails have less surface area, so the cats lose less heat through their tails. This allows them to better conserve energy and regulate body temperature (Source).

Short tails may also help cats avoid tail injuries during fights or accidents. And some speculate the tails shortened to help avoid tangling in vegetation on the island.

In summary, the short tails may have evolved to aid balance, temperature regulation, injury prevention, and mobility in the specific island environment (Source).

Environmental Factors

The island environment of Tashirojima has likely contributed to the unique traits seen in the cats that inhabit it. The island has a mild climate thanks to the warm Kuroshio Current that protects it from harsh winters (https://www.gov-online.go.jp/eng/publicity/book/hlj/html/202111/202111_05_en.html). This allows cats to thrive outdoors year-round. The terrain is rocky and mountainous, which may favor shorter tails that don’t get caught on vegetation. The diet consists mainly of fish, fruits, and vegetables provided by humans. The ready access to food means cats don’t need long tails for balance while hunting prey. The lack of predators on the island also reduces selection pressure for long tails. Overall, the island habitat shapes cat traits by allowing shorter tails to persist without major downsides.

Human Influences

One hypothesis is that human-driven selection over time has influenced the shorter tail trait in Cat Island cats. Fishermen initially brought cats to the island decades ago to control rodent populations that threatened fish stocks. Over time, humans may have deliberately or inadvertently bred cats with shorter tails, or culled cats born with longer tails (source). Shorter tails may have been preferred for perceived cuteness or novelty. Additionally, cats with longer tails may have been seen as less ideal rodent hunters for the fishermen. However, little direct evidence exists to confirm deliberate human breeding or culling biases over time.

Mainland cats in Japan tend to have longer tails than the cats on Cat Island. While there are some natural variations in tail length among cats in general, the short tails of Cat Island cats are quite pronounced in comparison.

Researchers have noted that the average tail length of a mainland Japanese cat is around 16 inches. However, the average tail length of a Cat Island cat is under 8 inches. Many have tails as short as 3-5 inches (Source: https://www.atlasobscura.com/articles/cat-island-japan-tashirojima-cat-tails).

The shortened tails are unique to Cat Island and not found in other cat populations in Japan or globally. Experts believe this distinct physical trait developed due to the isolation of the island cat colony over many generations. Without new cat DNA being introduced from mainland Japan, the Cat Island cats evolved tails shorter than the typical domestic cat.

While cats around the world exhibit some natural variation in tail lengths, the consistency of the shortened tails among Cat Island cats is noteworthy. This is likely an example of “island dwarfism,” where certain animal species confined to islands tend to evolve smaller bodies over time (Source: https://www.hakaimagazine.com/features/the-bobtailed-cats-of-japans-cat-island/). The short tails of Cat Island cats represent a unique evolutionary adaptation.

Conservation Status

The Iriomote cat population is estimated to be around 100 individuals as of 2023, down from estimates of 100-109 in 2008 and as high as 200-250 in the 1990s, indicating concerning declines (Mongabay). The Tsushima cat population is estimated to be around 100 as well, critically low compared to historic levels (The Japan Times).

Threats to the future of the Iriomote and Tsushima cats include habitat loss and fragmentation, invasive species, inbreeding due to small population sizes, road kills, and disease. Conservation efforts are underway, such as establishing protected areas, building wildlife road crossings, and breeding programs to increase genetic diversity, but the cats’ populations remain precarious.


Based on the evidence and analysis presented, the short tails of the cats on Cat Island are most likely the result of a genetic mutation that occurred sometime in the island’s history. While the exact mutation is unknown, it appears to have spread through the isolated island population, eventually becoming ubiquitous.

The short tails give the cats some advantages in their specific island habitat, including increased agility and balance in the rocky terrain, and resistance to overheating. However, the short tails do not seem to inhibit normal cat behaviors.

While human influences like selective breeding may play a small role, the consistency of the trait points to a dominant genetic factor unique to this island population. More genetic research is needed to pinpoint the exact gene variants involved. Additionally, studies comparing the island cats to mainland relatives could shed light on how the mutation arose and spread.

In conclusion, the short tails of Cat Island cats exemplify adaptive evolution in an isolated habitat. The island provides a valuable living laboratory to study evolution and genetic drift in progress. Going forward, it will be important to monitor and protect this unique population of cats.

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