- Other Geographic Terms
- island endemic
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. ("Mustela itatsi", 2012; Abramov and Wozencraft, 2012; Higash, 1988; Hooper, 2003)
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. (King, et al., 2007)
- Aquatic Biomes
- rivers and streams
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. (King, et al., 2007)
- Sexual Dimorphism
- male larger
- Range mass
- 150 to 450 g
- 5.29 to 15.86 oz
- Range length
- 40 to 52 cm
- 15.75 to 20.47 in
The mating process for (King, et al., 2007)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
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. (King, et al., 2007)
- Key Reproductive Features
- seasonal breeding
- gonochoric/gonochoristic/dioecious (sexes separate)
- Breeding interval
- Japanese weasels generally breed once yearly, although second litters may occur in years with abundant food resources.
- Breeding season
- Mating occurs from early May to late June or into August.
- Range number of offspring
- 2 to 12
- Average number of offspring
- Range gestation period
- 26 to 29 days
- Range weaning age
- 8 to 9 weeks
- Average age at sexual or reproductive maturity (female)
- 1 years
- Average age at sexual or reproductive maturity (male)
- 1 years
Females are solely responsible for parenting in (King, et al., 2007), 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.
Lifespan in 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.is similar to other members of the genus
- Typical lifespan
- 5 (high) years
- Typical lifespan
- Average lifespan
- 2 years
- Average lifespan
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. (King, et al., 2007)
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. (King, et al., 2007)
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. (King, et al., 2007)
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. (King, et al., 2007)
- Other Communication Modes
- scent marks
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. ("Mustela itatsi", 2012; Abramov and Wozencraft, 2012; Hamao, et al., 2009; Hooper, 2003; Kaneko, et al., 2009; Keishi, et al., 2002; King, et al., 2007)
- Primary Diet
- eats terrestrial vertebrates
- Animal Foods
- terrestrial worms
- aquatic crustaceans
- Plant Foods
- Foraging Behavior
- stores or caches food
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. (King, et al., 2007)
Japanese weasels help in controlling rodent and other small animal populations. There is also evidence that they are effective at spreading seeds through feces. (Sato, et al., 2006; Tsuji, et al., 2011)
- Ecosystem Impact
- disperses seeds
- Paragonimus ohirai
- Gnathostoma nipponicum
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. (Uchida, 1968)
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.
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. (Abramov and Wozencraft, 2012)
A common misunderstanding among people is that Japanese 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. (Masuda, et al., 2012)) and Siberian weasels (
Eric VanNatta (author), University of Wisconsin-Stevens Point, Christopher Yahnke (editor), University of Wisconsin-Stevens Point, Tanya Dewey (editor), University of Michigan-Ann Arbor.
living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.
uses sound to communicate
living in landscapes dominated by human agriculture.
young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.
- bilateral symmetry
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
an animal that mainly eats meat
uses smells or other chemicals to communicate
active at dawn and dusk
- active during the day, 2. lasting for one day.
animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.
- female parental care
parental care is carried out by females
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
- island endemic
animals that live only on an island or set of islands.
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
having the capacity to move from one place to another.
This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.
- native range
the area in which the animal is naturally found, the region in which it is endemic.
active during the night
having more than one female as a mate at one time
Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).
- scent marks
communicates by producing scents from special gland(s) and placing them on a surface whether others can smell or taste them
- seasonal breeding
breeding is confined to a particular season
remains in the same area
reproduction that includes combining the genetic contribution of two individuals, a male and a female
- stores or caches food
places a food item in a special place to be eaten later. Also called "hoarding"
living in residential areas on the outskirts of large cities or towns.
uses touch to communicate
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
Living on the ground.
defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement
- tropical savanna and grassland
A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.
A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.
- temperate grassland
A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.
uses sight to communicate
reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.
2012. "Mustela itatsi" (On-line). Encyclopedia of Life. Accessed August 17, 2012 at http://eol.org/pages/926025/overview.
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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.
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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.