Mustela itatsi

Geographic Range

Mustela itatsi was historically native to three of Japan’s four larger islands: Honshu, Kyushu, and Shikoku. Over the past century, they have been introduced to most other Japanese islands for the purpose of rodent control. The current range includes Hokkaido and the majority of the Ryukyu Islands.

• Biogeographic Regions
• palearctic palearctic
  • native native

• Other Geographic Terms
• island endemic island endemic

Habitat

Japanese weasels are found in a wide variety of Japanese ecosystems, but primarily mountainous and forested areas near moving water. Most hunting is done along rivers, but these weasels occasionally venture into grasslands or suburban areas.

In winter, these slim-bodied weasels spend most of their time beneath the snow chasing small rodents through a maze of tunnels. After catching and eating prey, Japanese weasels often enjoy the warmth of the quarry’s nest after eating.

• Habitat Regions
• temperate temperate
• terrestrial terrestrial

• Terrestrial Biomes
• savanna or grassland savanna or grassland
• forest forest
• mountains mountains

• Aquatic Biomes
• rivers and streams

• Other Habitat Features
• suburban suburban
• agricultural agricultural
• riparian riparian

Physical Description

As with all weasels, Mustela itatsi has a long, slender body with short legs and a stout neck and head. Japanese weasels are larger weasels; adult males have a body and tail length between 45 and 52 cm and an average weight of 400 g. Females are generally smaller. Their coats are usually golden-orange with lighter coloring on the belly, and darker markings near the face. In response to the shortening of daylight, weasels stop producing melanin and their coat turns white and becomes thicker in preparation for winter.

Although their body is well-suited for running down tunnels and into tight spaces, it is not very efficient for retaining heat and energy. Weasels must continually search for food to overcome this disadvantage.

• Other Physical Features
• endothermic endothermic
• homoiothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• male larger

Reproduction

The mating process for M. itatsi starts off with the male seeking out females by smelling and analyzing their scent marks. Once he tracks down a female, a mix of play and biting occurs from a few hours to several days. When the female is ready, she allows the male to bite her around the neck and pin her down. Copulation is brief, but may take place multiple times for each couple. Soon after, they go their own ways and likely never see each other again.

• Mating System
• polygynous polygynous

Mating occurs from early May to late June. However, if there is a particular abundance of food, mating may occur until August, producing a second litter during the season. After mating, gestation takes about 30 days. The number of kits varies from 2 to 12, but is usually 5 or 6. It takes 8 weeks to fully be weaned and independent. Japanese weasels are sexually mature at one year old.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• viviparous viviparous

Females are solely responsible for parenting in Mustela itatsi , from conception to independence. Males leave females once mating is complete. Mothers will build nests in abandoned holes, cavities, or logs using grasses, feathers, and animal fur. Once the kits are born, their mother feeds them milk until their canines develop fully and they can consume flesh. Once old enough to move about, young weasels practice valuable hunting skills through play behavior. Soon after, they tag along with their mother to go hunting. Once they can hunt on their own, they’re considered independent and leave their mothers protection to find their own territory.

• Parental Investment
• altricial altricial
• female parental care female parental care
• pre-hatching/birth
  • provisioning
    • female
  • protecting
    • female
• pre-weaning/fledging
  • provisioning
    • female
  • protecting
    • female
• pre-independence
  • provisioning
    • female
  • protecting
    • female

Lifespan/Longevity

Lifespan in Mustela itatsi is similar to other members of the genus Mustela . As a close comparison, M. sibirica has lived up to 8 years in captivity. Longevity in the wild is highly dependent on food availability. Average lifespan is likely to be 2 to 3 years.

Behavior

Japanese weasels are solitary animals, with the exception of mating courtships, and mothers with young. They are very territorial and will aggressively defend their home range, especially dominant males. All weasels present an aggressive defense against threating animals, even against much larger species. Also, when cornered or very frightened, weasels release a potent dose of musk to deter attackers.

Japanese weasels are also expert hunters, chasing down prey by any means, including running down tunnels, climbing trees, or swimming. Anywhere prey can go, the weasel can follow. Very high hunting success is achieved through these abilities. They are both diurnal and nocturnal.

• Key Behaviors
• terricolous
• diurnal diurnal
• nocturnal nocturnal
• crepuscular crepuscular
• motile motile
• sedentary sedentary
• solitary solitary
• territorial territorial

Home Range

There is no information on home range size in Japanese weasels.

Communication and Perception

In order to communicate with other weasels or other animals, Japanese weasels use two main modes of communication: chemical and acoustic. Individuals secrete a substance known as musk from their characteristic anal glands, used in chemical communication. Weasels are territorial and establish territorial boundaries by rubbing their glands over obstacles such as branches and stones. Scent marks communicate gender, age, social status, health, and breeding condition.

Japanese weasels emit a wide range of calls and sounds. Primary calls include a low intensity trill, chirp, bark, screech, and hiss. Trilling generally signifies comfort when a mother is with her young. Chirping is another content call when danger is not present. Barking, screeching, and hissing all indicate imminent danger.

• Communication Channels
• acoustic acoustic
• chemical chemical

• Other Communication Modes
• scent marks scent marks

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

Food Habits

Since they are able to live in a wide range of Japanese habitats, these weasels have a wide range of prey options. They prefer to catch live prey such as rodents, amphibians, reptiles, birds, and some crustaceans. These weasels are also nest raiders, and enjoy bird eggs or young chicks. A common prey bird species is the Japanese bush warbler ( Cettia diphone ). When prey is scarce they resort to eating various fruits and berries. When food is abundant it is common for weasels to cache food items for later consumption.

• Primary Diet
• carnivore carnivore
  • eats terrestrial vertebrates

• Animal Foods
• birds
• mammals
• amphibians
• reptiles
• fish
• eggs
• insects
• terrestrial worms
• aquatic crustaceans

• Plant Foods
• fruit

• Foraging Behavior
• stores or caches food stores or caches food

Predation

Despite their carnivorous lifestyle, the small body size of Japanese weasels make them a target to some large predators, mainly birds of prey. Their musky scent makes them less palatable to mammalian predators.

Ecosystem Roles

Japanese weasels help in controlling rodent and other small animal populations. There is also evidence that they are effective at spreading seeds through feces.

• Ecosystem Impact
• disperses seeds

Economic Importance for Humans: Positive

In the past century Japanese weasels have been introduced to many of Japan's small islands to kill rats that were damaging crops. Along with the use of some rodenticide, the weasels helped reduce rat populations.

Japanese weasels are also trapped and used in the fur industry.

• Positive Impacts
• body parts are source of valuable material
• controls pest population

Economic Importance for Humans: Negative

Japanese weasels also occasionally prey on domestic birds, such as chickens and ducks.

Conservation Status

Although their populations are in slight decline, Japanese weasels are listed on the IUCN Red List as Least Concern because of their widespread population across Japan. The primary threat to Japanese weasels is habitat loss due to residential and commercial development.

Other Comments

A common misunderstanding among people is that Japanese weasels ( Mustela itatsi ) and Siberian weasels ( Mustela sibirica ) are the same species with different common names. Recent studies have proven this to be false. These two species are distinguished from one another by specific body/tail ratios and unique genotypes.

Additional Links

Encyclopedia of Life

Contributors

Eric VanNatta (author), University of Wisconsin-Stevens Point, Christopher Yahnke (editor), University of Wisconsin-Stevens Point, Tanya Dewey (editor), University of Michigan-Ann Arbor.

References

Abramov, A., C. Wozencraft. 2012. "Mustela itatsi" (On-line). ICUN Red List of Threatened Species. Accessed August 10, 2012 at http://www.iucnredlist.org/details/41656/0 .

Hamao, S., K. Nishimatsu, T. Kamito. 2009. Predation of Bird Nests by Introduced Japanese Weasel Mustela itatsi on an Island. Ornithological Science , 8/2: 139-146. Accessed August 18, 2012 at http://www.bioone.org/doi/abs/10.2326/osj.8.139 .

Higash, H. 1988. "Ecological study of Japanese Weasel (Mustela itatsi) in Tamagawa River by radio-telemetry method" (On-line). The Tokyu Foundation for Better Environment. Accessed August 18, 2012 at http://www.tokyuenv.or.jp/archives/a_research/多摩川河川敷におけるイタチの生息状況の把握な?lang=en .

Hooper, R. 2003. "Animal Tracker Japanese Weasel" (On-line). The Japan Times Online. Accessed August 10, 2012 at http://www.japantimes.co.jp/text/fe20030508at.html .

Kaneko, Y., M. Shibuya, N. Yamaguchi, T. Fujii, T. Okumura, K. Matsubayashi, Y. Hioki. 2009. Diet of Japanese Weasels (Mustela itatsi) in a Sub-Urban Landscape: Implications for Year-Round Persistence of Local Populations. Mammal Study , 34/2: 97-105. Accessed August 10, 2012 at http://www.bioone.org/doi/abs/10.3106/041.034.0205 .

Keishi, S., O. Go, S. Takeshi, N. Yasuhiko, T. Kojun, K. Yoshitsugu. 2002. Food Habits of Introduced Japanese Weasels(Mustela itatsi) and Impacts on Native Species on Zamami Island.. Mammalian Science , 42/2: 153-160.

King, C., R. Powell, C. Powell. 2007. The Natural History of Weasels and Stoats . Oxford, New York: Oxford University Press.

Masuda, R., N. Kurose, S. Watanabe, A. Abramov. 2012. Molecular phylogeography of the Japanese weasel, Mustela itatsi (Carnivora: Mustelidae), endemic to the Japanese islands, revealed by mitochondrial DNA analysis. Biological Journal of the Linnean Society , 29/5: 1095. Accessed August 18, 2012 at http://onlinelibrary.wiley.com/doi/10.1111/j.1095-8312.2012.01948.x/abstract .

Sato, H., K. Suzuki, A. Osanai, M. Aoki. 2006. Paragonimus westermani and some rare intestinal trematodes recovered from raccoon dogs (Nyctereutes procyonoides viverrinus) introduced recently on Yakushima Island, Japan.. The Journal of Veterinary Medical Science , 68/7: 681-687.

Tsuji, Y., T. Tatewaki, E. Kanda. 2011. Endozoochorous seed dispersal by sympatric mustelids, Martes melampus and Mustela itatsi, in western Tokyo, central Japan. Mammalian Biology , 76/5: 628-6333. Accessed August 10, 2012 at http://www.sciencedirect.com/science/article/pii/S1616504711000036 .

Uchida, T. 1968. Observations on the Efficiency of the Japanese Weasel, Mustela sibirica itatsi Temminck & Schlegel, as a Rat-Control Agent in the Ryukyus. Bulletin of the World Health Organization , 39/6: 980. Accessed August 10, 2012 at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2554576/pdf/bullwho00233-0136.pdf .

2012. "Mustela itatsi" (On-line). Encyclopedia of Life. Accessed August 17, 2012 at http://eol.org/pages/926025/overview .