Weasels are popular for their cute appearance, as they have small bodies and lovely eyes. Especially their tails are big and fluffy, and make you want to touch them.
However, do you know that weasels are very ferocious, contrary to their appearance? In this article, we will look at the unknown ecology of weasels and solve some questions you may have!



~ Basic information. ~

Carnivora Caniformia Mustelidae Weasel genus.

The size of the Japanese weasel that inhabits the Japan is as follows.
Length : about 30-37cm. Tail length: about 12-16cm. Weight: about 290-650g.

Also, the size of weasels varies depending on the species. The American least weasel weighs about 30 to 70 grams, and is one of the smallest in the cat family. Also, in general, males are much larger than females.

The appearance of weasels is characterized by their long bodies and short limbs. Also, their small round ears are cute.


We mentioned that the least weasel is the smallest in the cat family, but actually the weasel group itself is quite small.

They are widely distributed throughout the world, and can be found from subtropical to cold regions in Japan, Eurasia, Africa, and America. They used to live mainly in mountainous and riverine areas, but now they can be seen around urban areas and houses.

However, they are not as common as dogs or cats, so you might be surprised if you see them. By the way, the ones you mainly see in Japan are the native Japanese weasel and the Siberian weasel that came from Eurasia. It is said that most of the ones you see in the city are Siberian weasels.


So where do Japanese weasels live?

Japanese weasels live in traditional mountainous and riverine areas, but there are also cases where they make nests under the floor or in the ceiling of houses.

Also, the behavior range of weasels changes depending on the sex. Females have a fixed behavior range, but males behave so that they overlap with several females’ behavior ranges. Weasels have a polygamous breeding system, so that may be related.


Next, let’s look at the behavior of weasels.

The surprising behavior of weasels is that they can easily pass through gaps of only a few centimeters square. This behavior may be similar to cats, who can pass through if their head goes through.

Moreover, they are good at swimming, and they can easily climb vertical trees or walls. Their agility and activeness are hard to imitate for us humans.

Weasels have paired anal glands in their anus, and when they feel danger, they secrete a strong-smelling body fluid from their anal glands. This behavior became the origin of the phrase “weasel’s last fart”, which means “the last resort when cornered”.

The personality of weasels is not timid, but rather quite ferocious. I understand that they look cute, but don’t touch them casually. They don’t usually attack aggressively, but if you touch them carelessly, they will bite or scratch you. Also, be careful because they may have parasites that can infect humans.

To keep a weasel as a pet.

If you want to keep rare animals, you need to follow the laws set by each country. In this article, we will introduce whether you can keep weasels at home in Japan.

The most famous weasel to keep as a pet is the ferret. Ferrets are a kind of weasel, and are said to be subspecies of the European polecat or the steppe polecat.

They are often sold at pet shops, so they are not too difficult to obtain.


What are the personality traits of ferrets?

Ferrets are different from other weasels in that they are easy to get attached to humans. They are not obedient and loyal like dogs, but rather similar to cats, and have a personality that likes to play freely.

They don’t need to be walked, so some people may appreciate that they don’t take much trouble.

How much does a ferret cost?

The price of ferrets varies widely depending on the type. Generally, they are sold for about 20,000 to 50,000 yen, but some popular or rare types can exceed 100,000 yen.

If you don’t have any particular preference, it might be a good idea to visit a nearby pet shop first.

What do you need to keep a ferret?

There are some things you need to have when you keep a ferret, but basically you should be fine with the following three things.

  • Cage.
  • Toilet.
  • Bed.

Ferrets can be kept free-range, but you should prepare a cage to prevent accidents. To avoid lack of exercise, it is recommended to choose a large cage for ferrets as much as possible.

Ferrets have a habit of going to the toilet in the corner of the room, so try to place the toilet as close to the corner as possible. To prevent the smell from accumulating, you need to clean it as often as possible.

Finally, you will prepare a bed for your ferret. It doesn’t matter what kind of bed you use, but there are cages that have a toilet and a bed set, so it might be easier to use a set at first.



Weasel’s Q&A.

What is the origin of the name Weasel?

They are called ‘Weasel’ in English, but actually they are called ‘Itachi’ in Japanese. In this article, we will introduce why they are called Itachi in Japanese and the origin of their name.

IThere are several theories about the origin of the name Itachi.

The first one is ‘Uotachi’, which means ‘fish cutter’. Itachi are good at catching fish and eating them up, and this is where the name comes from.

The second one is ‘Hitachi’, which means ‘fire stand’. Itachi’s fur is red, and their standing posture looked like a pillar of fire, and this is thought to be the origin.

The third one is ‘Ikitachi’, which means ‘breath cutter’. It is said that they stop their breath and sneak up on their prey when they hunt.

The fourth one is ‘Itahehanachi’, which means ‘painful fart release’. It comes from the strong smell they release when they are in a pinch.

The last one is ‘Ittachi’, which means ‘one stand’. Itachi have a habit of stretching and checking their surroundings. It is a theory that adding the prefix ‘I’ to ‘Tatsu’, which means ‘stand’, makes ‘Ittachi’, and then it becomes Itachi.

The origin of animal names is interesting because there are various theories.

How did you like Itachi?

It is rare to have so many theories, but they are all interesting and seem true!


Why do weasels live there?

Weasel are basically very wary, so they don’t appear in places where people can see them easily. Also, they can easily climb walls and trees, so they prefer places where they can move in three dimensions. Therefore, many of them live in mountainous areas, but there are also cases where they settled in houses.

They seem to make nests in the gaps of stone walls or under the floor, but they also often make nests in the ceiling. They are said to use the insulation materials used in the house as their nests. It is troublesome for us humans to have the insulation materials destroyed, but Itachi must be desperately trying to keep warm.


What are weasels eating?

Weasel are omnivorous animals, but they have a strong tendency to be carnivorous. Their main food sources are mice, frogs, birds, fish, insects, etc.

They like fruits such as persimmons among plants.

Also, because they have a ferocious personality, they sometimes prey on larger animals such as chickens or rabbits. They may also bite humans, so try not to touch them if possible.


How long does a weasel live?

The lifespan of weasels is about 1.5 years in captivity. In the wild, they are said to live for about 2 years. Animal lifespans are short compared to humans, but weasels are even shorter-lived.

They are said to become adults in about a year, so they may mature quickly. But it seems a little sad to think that they only live for 2 years at most from a human perspective.


What are the natural enemies of weasels?

The natural enemies of weasels are foxes, wolves, and birds of prey. They can’t compete with larger carnivores such as foxes and wolves, or raptors such as eagles and owls.

However, they can sometimes escape by emitting a strong odor, and weasels are quite tricky animals. It is exactly ‘the weasel’s last fart’.

Are weasels different from stoats, minks and civets?

There is a creature called the okojo that resembles a weasel. There are also others such as minks and ferrets. However, these are all classified as species of the weasel genus, so in a broad sense they are the same as weasels.


On the other hand, there is a creature called the masked palm civet.

The masked palm civet is classified as a species of the masked palm civet genus, so it is different from the weasel, but it looks very similar. The way to tell them apart is easy: just look at the pattern on their face!

If there is a white line from the nose to the top of the head, it is a masked palm civet. The masked palm civet is written in kanji as ‘white nose core (heart)’, so it is literally ‘the name reflects the nature’.


What is the relationship between weasels and humans?

For humans, weasels were cherished as pets. On the other hand, they were also hunted for their fur.

As pets, ferrets are famous and are believed to have been kept for about 3000 years.

On the other hand, a type of weasel genus called mink has increased in value for its fur and is traded as a luxury clothing item. You may have heard of mink coats and such.

However, recently the value has stabilized and they are no longer being overhunted. Also, besides fur, they are used for high-quality brushes.

出典:https://commons.wikimedia.org/wiki/File:Norka amerykańska hodowlana.jpg

Was weasel considered a Japanese folk monster?

In Japan, there was an old custom of thinking of weasels as yokai, or supernatural creatures. They were believed to cause various strange phenomena, and in old books they are said to start fires or bring bad luck.

They were also said to transform, like raccoon dog and foxes. Also, one of the famous things that was thought to be the work of weasel yokai is ‘kamaitachi’, or sickle weasels.


Was “kamaitachi” thought to be the work of a weasel?

‘Kamaitachi’ is a phenomenon where the skin is suddenly cut without doing anything.

It is now known that dry skin cracks when it is shocked, but in the past it was said to be the work of weasel yokai. It was called ‘sickle weasel’ because it was cut like it was slashed by a sickle.

However, there is also a theory that the origin of the word is ‘kamae tachi’, or ‘ready sword’, in which case the weasel has nothing to do with it. I wonder if some people feel a sense of familiarity with the technique called ‘kamaitachi’ in various fantasy works?


Is weasel a beneficial beast? Vermin?

Originally, Japanese weasels only lived in some regions, but they were brought to various places as beneficial animals for rodent control.

If it was only rodent control, they would have remained beneficial animals, but weasels are ferocious omnivorous animals. They finally started to attack crops and livestock such as chickens.

Also, because of the damage caused by their feces and urine, the aspect of being harmful animals has become stronger than the aspect of being beneficial animals. It may be human selfishness to say so, but we want to create an environment where we can coexist with natural animals as much as possible.




Type of Weasel.

  • Mountain weasel.
  • Ermine.
  • Long-tailed weasel.
  • Yellow-bellied weasel.
  • Least Weasel.
  • Siberian weasel.
  • Japanese weasel.
  • Back-striped weasel.
  • Malayan weasel.
  • American mink.
  • Sea Mink.
  • European mink.
  • European polecat.
  • Steppe polecat.
  • Black-footed ferret.
  • Amazon Weasel.
  • Colombian weasel.

The sea mink became extinct in the mid-19th century.

The ferret is sometimes considered a subspecies of the European polecat or the steppe polecat, but the details are not known.

The Japanese weasel is sometimes considered a subspecies of the Siberian weasel.








国土交通省 中国地方整備局 太田川河川事務所(太田川生物誌)