lemming

Lemmings belong to the rodent hamster family and have four genera: ring-necked lemmings, lemmings, lemmings, forest lemmings, and swamp lemmings.

Chinese scientific name
lemming
world
animal kingdom
door
Vertebrate phylum
class
Mammalia
eye
Rodentia
section
Hamster family
genus
Lemmings
Distribution area
High-latitude coniferous forests in northern Norway and Eurasia

lemming

Lemmings are a very common, cute mammalian small animal, living in the Arctic all year round, with an oval body,

Lemmings have short legs, small ears and soft fur. In addition to the tail, the whole body is 10 to 18 cm long. The upper layer of the coat is light gray or light reddish brown , ( sometimes orange red ) , the lower layer is lighter in color , and some lemmings have a completely white coat in winter , which is conducive to protecting themselves.

lemming

The high-latitude coniferous forests of northern Norway and Eurasia feed on roots, twigs, grasses and other plant materials, and predators include owls, skuas, gray-black seagulls, rough-legged bald eagles, snowy ospreys, arctic foxes, weasels, polar bears, etc.

lemming

In the Arctic tundra region, over-population and lack of food lead to a rapid migration of large numbers of lemmings. The researchers found that the critter could migrate up to 10 miles in a day. For some of the weak, this migration is too fast, and if it falls behind, it will die.

Lemmings move from dry areas in winter to wet areas in summer in the spring, and their population reaches the peak of the population in about three to four years, and in the late summer or autumn of the peak year, it will move from high-density areas to low-density areas.

lemming

Lemmings run from spring to autumn

Fertile, very fertile, gestation period of 20 to 22 days, a litter can give birth to 12 litters, 7 to 8 litters a year, and its male-to-female ratio accounts for about 3:1, but in early spring the ratio of about 1:1. Males have only one form of chromosome xy, but females have three types: xx, x’x, and x’y, of which x’y has higher reproductive potential.

Lemmings usually live no more than one year. In terms of field of activity, the male is about 2000 square meters, and the female is about 300 square meters. Lemmings mature for more than 44 days in males and 20 to 40 days in females, and if lemmings weigh less than 20 grams in the summer, they will stop growing in the winter until spring, and then mature sexually.

lemming

Lemmings are the most fertile of all known animals in the world, they can give birth to 7 to 8 litters a year, each litter can give birth to 12 cubs, and it only takes more than 20 days for the cubs to mature and begin to give birth. Let’s calculate its reproductive capacity: if a pair of lemmings were born in March, if they had given birth to a total of 7 litters a year, each with 12 litters, for a total of 84, this would be their second generation, that is, sons and daughters. Suppose that each fetus is 6 males and 6 females, then it is 6 pairs. After 20 days, the first 6 pairs of children began to give birth, each litter 12, all at once can give birth to 72, a total of 6 can give birth to 6, then 432. After 40 days, the 6 pairs of the second litter also invested in the fertility army, and they could give birth to a total of 5 litters, or 360 if each litter was 12. And so on, so how many grandchildren and grandchildren can they have? There can be a total of 2160. This is the third generation. After 40 days, the first 36 pairs of the third generation also began to breed, and their first litter could give birth to 432, a total of 5 litters, 2160. There are also second to seventh births of the third generation, so the total number of lemmings in the fourth generation is 15,120. According to this calculation, the fifth generation is 90720, the sixth generation is 326592, the seventh generation is 653184, and the eighth generation, the last batch of the year, is 559872. From two in March to the end of August and the beginning of September, it will become a huge team of 1647086! Even half of them died due to climate, disease and natural enemies, and there were 820,000 more. The density can reach as many as 250 per hectare. This is a mystery of lemmings.

lemming

When the lemmings swell dramatically to a certain density, for example, after there are hundreds of them per hectare, a strange phenomenon occurs: at this time, almost all the lemmings suddenly become restless, they run from side to side, noisy, and stop eating, as if the great trouble is coming, and the end of the world is coming. At this time, the lemmings are no longer timid and afraid, running when they see people, but on the contrary, in front of any natural enemy, they appear brave and abnormal, fearless, with obvious provocation, and sometimes even take the initiative to attack, which is really a bit of a look of fearlessness. What is even more difficult to explain is that at this time, even their skin color will change significantly, from gray to bright orange, making it particularly prominent. The only possible and plausible explanation for all these strange phenomena added together is that they are no different from suicide in order to try their best to attract the attention of predators such as owls, skuas, gray-black seagulls, rough-legged bald eagles, arctic foxes, and even polar bears, so that they can be devoured and consumed as much as they can. This is the second secret of lemmings.

lemming

When the number of lemmings is too large, and the number of natural enemies is always limited, no matter how much they expose themselves, they have little effect. So they show a very strong sense of migration, gather together, gradually form large groups, at first there seems to be no direction and goal, wandering around, as if they were in a hurry before departure, as if they were preparing. But then, not knowing who gave the order or who took the lead, they suddenly set out in the same direction. It is often a daytime break to eat, at night to move forward in the dark, along the way there are rats to join, and the team will become larger and larger, often up to millions, every mountain, wading in the water, bravely forward, forward and backward, along a straight line of courageous progress, never detour, not stop, straight to the sea, still without fear, jump down one after another, until it is engulfed by the surging waves, the whole army is destroyed. This is the third mystery of lemmings.

lemming

A popular “beautiful article” signed “Sandnes” on the Internet, “The Vast Sacrifice of the Sea – Rushing to the Covenant of Death”, transferred from the “Reader” No. 15, 2005, is said to be a Norwegian cancer patient in the journey of following the lemmings to death, epiphany of the true meaning of life: do not fear death, because life and death are part of life. However, from the content and writing point of view, it is not like a translation work, when it is a counterfeit work of a domestic writer, which depicts himself tracking and witnessing millions of lemmings for the benefit of the species, after a long journey to the sea after a collective jump to commit suicide, in fact, it is adapted from the popular science article introducing the “lemming mystery” in China.

lemming

Legend has it that when the lemmings reach their peak, they spontaneously migrate en masse and commit suicide by rushing to the sea, leaving only a few of their kind to stay and take on the sacred task of passing on the generations. In Disney’s 1958 documentary “White Wilderness”, it recorded the scene of lemmings migrating in droves and finally jumping into the sea to commit suicide, accompanied by a very sensational commentary. This Oscar-winning film has a profound impact, making the moving legend of the lemming rat rushing to the covenant of death a household name in the West.

lemming

But the scenes from that documentary were faked. The film was shot in the Canadian province of Alberta, an area that doesn’t produce lemmings. The crew went to the Arctic to buy dozens of lemmings from Inuit children, let them run on a snow-covered turntable, shot from all angles, and the editing showed the migration of thousands of lemmings. After that, the camera crew took the lemmings to the cliff, hoping to film them jumping into the river below the cliff and drowning. Unexpectedly, the lemmings were reluctant to jump down, and after waiting for two days, the impatient photography team drove the lemmings off the cliff and artificially created a suicide by jumping into the sea.

lemming

Why the lemming population changes periodically is an inconclusive biological subject, which may be related to natural predators, food, climate, seasons and other factors. For example, an obvious but unproven explanation is that the dramatic increase in lemming populations destroyed vegetation and led to food scarcity, resulting in large numbers of lemmings starving to death. Then the vegetation began to recover, and a new cycle appeared. In fact, this is not a phenomenon unique to lemmings, and the populations of other small animals that survive under harsh conditions will undergo similar periodic changes.

lemming

While there are different views on the answer to this question, experts agree on this point: Lemmings do not commit mass suicide. When lemmings increase dramatically and local food becomes scarce, lemmings, like other animals, spread elsewhere. It has been observed that in the mountains of Norway, lemmings from the mountains spread towards the valley, and some of them gradually reach the lake and the sea, where they are settled. But as more and more latecomers came, some would try to swim to the other side, and some would drown. This may be the source of the myth of lemming mass suicide.

lemming

In recent years, some experts have also tried to explain the mystery of the decline in lemmings in terms of changes in their own numbers. For example, as the population density increases, lemmings experience more social communication and stress with each other, leading to changes in hormone levels in the body, which makes them less fertile and more aggressive. When the population density is too large, the lemmings react not to sacrificing themselves, but to attack other lemmings, and even to fratricidal killing.

lemming

The myth of lemmings rushing to the covenant of death will not disappear as easily as the myth of lemmings falling from the sky. No matter how much experts try to clarify it, this myth will continue to be passed down as a scientific fact, as an educational natural wonder. After all, for many, a beautiful lie trumps a cold truth.

lemming

Lemmings are a very ordinary, cute little animal, living in the Arctic all year round, oval in shape, short limbs, smaller than ordinary mice, up to 15 centimeters long, with a thick and short tail, small ears, and timid eyes, but when forced to go nowhere, it will also be angry and fight back. The Eskimos called it an animal from the sky, while Scandinavian farmers simply called it a “sky rat.” This is because, in a given year, their number will increase greatly, as if the heavenly soldiers and heavenly generals have suddenly arrived.

lemming

Although lemmings are mammals, their reproductive ability is very strong. In March in the Arctic, when the rough screams of arctic foxes for courtship break the tranquil tundra, lemmings have already given birth to their first litters and are busy raising their newborn children under the snow. Catching up with the good years, a female lemming can produce 6 to 7 litters a year, newborn lemmings can mate 20 to 30 days after birth (the highest record is 14 days after birth), after a 20-day gestation period, you can give birth to a litter of lemmings, each litter can give birth to 12, according to this rate, a female mouse can produce thousands of offspring a year, it is indeed amazing!

lemming

Adapted to the high degree of fertility, the lemming rat consumes an amazing amount of energy in order to replenish the energy consumed during reproduction.

A meal can eat food equivalent to twice its own weight, and the diet is wide, almost all Arctic plants such as grass roots, grass stems and moss are among its recipes, it can eat 45 kilograms of food a year, so people jokingly call lemmings “fat and busy harvesters”.

Lemmings have many natural predators, such as owls, skuas, snowy ospreys, arctic foxes, polar bears, etc. all feed on lemmings. A pair of snowy ospreys and their children can eat 100 lemmings a day. Even herbivorous reindeer will kill lemmings, trample them to death with their hooves, and then eat them, which can be regarded as improving their lives.

What is of most interest to people is the cyclical number fluctuations of lemmings and their natural enemies. Every 3 to 4 years, lemmings increase dramatically and usually begin to decline after only a year. The results of the survey proved that in some years whole litters of lemmings could be found in the stomachs of arctic foxes, indicating that arctic foxes dug up lemmings from under the snow. The increase in the number of lemmings provides excellent conditions for the reproduction of arctic foxes, when 100% of the fox holes in the tundra area are inhabited by arctic foxes, with an average litter of 8 litters per litter; when the number of lemmings decreases, the arctic fox has a serious lack of food sources, and has to feed on foods with low nutritional value, and the female foxes have declined physical fitness and are not pregnant, even if pregnant, the young foxes born are weak and sickly, and will soon die. In this way, for 1 to 2 consecutive years, the population of arctic foxes will decrease sharply. Snowy ospreys feed on lemmings, and the same is true, when the lemming population increases, the number of snowy ospreys will also increase, and when the lemming population decreases, a large number of snowy ospreys are forced to move south due to hunger. Therefore, in North America, a large number of migrations of this snowy wagtail can be seen every 3 to 4 years, and between the two migrations, the snowy osprey is rarely seen.

lemming

In normal years, lemmings reproduce only a small amount, causing their population to increase slightly, or even stay the same. It is only in good years, when the climate is suitable and food is plentiful, that they multiply in unison, causing their numbers to increase dramatically, and once they reach a certain density, for example, after 1 hectare and a few hundred, strange phenomena occur: at this time, almost all the lemmings suddenly become restless, they run from side to side, noisy and endless, they stop eating, it seems that the great trouble is coming, and the end of the world is coming. At this time, they are unusual, no longer timid and afraid, running when they see people, but on the contrary, in front of any natural enemy, they do not change their color, fearless, and sometimes even take the initiative to attack, really a little bit of heaven is not afraid. Even more incredibly, even the color of their coats has changed significantly, from a gray-black that is easy to conceal to a clearly targeted orange-red color in order to attract the attention of predators and to devour and consume them more. At the same time, there is also a strong sense of migration, and they have gathered together to form large groups. First it is chaotic everywhere, like the hectic chaos before departure, and then at the behest of someone, it will go in a certain direction, starry night, running wildly, and the sea is always their final destination. Interestingly, when they carry out this great migration of death, they always leave a small number of caretakers of the same kind and take on the sacred task of passing on the generations so that they will not become extinct. All of this seems to have been carefully considered and carefully arranged.

lemming

Of all the Arctic animals, the little lemming is perhaps the most mysterious and puzzling. Among its many mysteries, the most inexplicable is the so-called “Great Migration of Death”.

As early as 1868, it was recorded that a strange phenomenon had been noticed: in the spring, when the sky was clear and the sun was shining, a ship full of passengers was sailing on the turquoise sea, and suddenly a large piece of something was squirming in the sea far from the Norwegian coastline. It turned out to be a large number of lemmings swimming in the sea, one group after another from the coast all the way to the middle of the sea, swimming in front, when the physical strength was exhausted, it drowned in the sea, followed by the lemmings still desperately, continue to move forward, until drowning. Afterwards, tens of thousands of drowned lemming corpses floated on the surface of the sea.

To this day, this phenomenon still occurs repeatedly.

lemming

As for why lemmings commit suicide en masse, scientists, despite extensive observations and studies, are still divided into disagreements and cannot come up with a convincing explanation. Some believe that the collective suicide of lemmings may be related to their high reproductive capacity. Lemmings like to live alone and quarrel, and when their populations are too high, they become extremely excited and restless, at which point they will squeak in their snowy burrows, running around, fighting and making trouble. Therefore, some people believe that due to its excessive fertility, lemmings do not have enough food and living space, so they have to run to other places. It is worth mentioning that lemmings are extremely widely distributed

In addition to Northern Europe, it is found in northwestern America, the southern steppes of Russia, and all the way to Mongolia, but only lemmings in Northern Europe and Norway have periodic mass suicide by jumping into the sea. Therefore, some biologists further explain that tens of thousands of years ago, the Norwegian Sea and the North Sea were much narrower than they are now, when lemmings could swim to the other side of the sea, and in the long run, from generation to generation, a genetic instinct was formed. However, due to the movement of the earth’s crust, the current Norwegian and North Seas are much wider than in the past, but the genetic instincts of lemmings are still at work, so the lemmings still migrate and are finally drowned in the sea, performing a tragedy of collective suicide of lemmings.

However, there are serious deficiencies in this doctrine. Because lemmings are rodents, they feed on almost all the plants in the Arctic, and even when they reach a density of 250 per hectare, they are rare, so lemmings are not migrating because they do not have enough food and living space. What is even more convincing is that lemmings will never stay in areas with abundant food during migration, even if they encounter a wide area. Moreover, lemmings have also moved into the Barents Sea and north along the Arctic Ocean, and according to the above view, many years ago, there should have been land in the northern part of the Barents Sea, otherwise, why did lemmings move north? In this regard, scientists in the former Soviet Union have proposed a new explanation, 10,000 years ago, the earth was in a cold ice age, the Arctic Ocean surface formed a thick layer of ice, wind and birds respectively brought a large amount of sand and plant seeds to the ice, so every summer, here is still green grass, lemmings can survive here. It was only later that climate change led to the disappearance of the original ice, and the lemmings that now jump north into the Barents Sea are looking for their former habitation. This explanation, while justified, lacks sufficient evidence and is therefore still unsatisfactory.

lemming

Another theory is that due to the increase in the number of populations, resulting in excessive activity of lemmings (nervous, running east and west) and increased community pressure, the result is that the lemmings’ adrenal glands increase, the nerves are highly tense, they appear restless, and the desire to exercise is very strong, so they begin to disperse and migrate, some attempt to cross rivers, lakes and seas, although lemmings are good at swimming, but eventually drowned due to lack of physical strength, some just ran to the marginal areas where food is scarce, starving, and the exuberant sexual desire also declined. As a result, the population began to decline on a large scale. However, this doctrine also has certain flaws, because the consequences of high density often do not appear immediately in the contemporary era, but only in the next generation

effect. In short, on the issue of lemming collective suicide, there are external environmental conditions, there are also lemmings themselves physiological, behavioral, and even genetic factors, in the face of such a complex problem, there is still a lot of research work to be done, only in this way, can gradually uncover the mystery of lemming collective suicide.

In addition, scientists who study the life cycle of lemmings have also found that during the period of sharp increase in their numbers, the chemical processes and endocrine systems in lemmings also change. It has been suggested that these changes may be the switches in an organism that control the number of its populations, and when they reach a certain level, they will cause a large number of collective deaths of the population. But whether lemmings committed mass suicide or went astray in the process of migration, fell into the sea and drowned, is still a difficult mystery in the biological world.

lemming

Lemmings are the bosses of the Arctic steppes, and their fertility rate is so fast that they can give birth to up to 20 animals per litter. It takes 20 days to mature. If a pair of rat men and women are committed to fertility from the spring, they will produce hundreds of thousands of offspring by the autumn. Every three to four years, lemmings are so numerous that they eat all the edible things in the prairie. At this time, they have to consider the affairs of future generations, how to eliminate the excess quantity? death! Active death is the best way.

At this time, the lemmings suddenly changed from the original gray-black to bright orange-red, exposing their location and attracting predators to hold a belly burial for themselves. But no matter how hard the foxes and owls tried, they couldn’t eat all the lemmings.

So the lemmings gathered, and hundreds of thousands, millions, of them began the most tragic journey of their lives. They rushed to the sea, the lemmings in front of them built bridges in the water, filling in the rivers and ponds with flesh, and the lemmings in the back stepped on the corpses of their own kind and continued to advance. Wherever the army went, the plants were all eaten, the meadows became wastelands, and when their death teams came to the seashore, millions of lemmings were hugged together and tumbled in the water like a hill…

The origin of the lemming’s name is because of this death journey. Pittke in the United States used the theory of nutritional restoration to explain the suicide of lemmings: when the rat population reached its peak, the vegetation was destroyed by excessive nibbling, the food was insufficient, and the hidden conditions deteriorated, so they had to die except for a few to reproduce. By the time the plants recover, their numbers have risen steadily.

lemming

The high latitudes of the Northern Hemisphere are dominated by the Arctic tundra, where a rodent called a lemming mouse lives, and its population cycles cyclically, surging to a certain number and inexplicably decreasing sharply. This mysterious phenomenon has plagued the biological community for nearly a century, and lemmings regularly commit “mass suicide.” A team of three biologists in Europe said that after 15 years of field observations, they found that the four natural enemies of lemmings are the determinants of changes in their populations.

The “Four Natural Enemies” influence the rise and fall

In the 75-square-kilometre Karup River basin in northeastern Greenland in the Arctic region, a team of scientists composed of Olivier Gilger and Ilka Hansky of the University of Helsinki in Finland and Bernoit Sitler of the University of Freiburg in Germany conducted 15 years of field observations and collected valuable data on lemmings and their natural enemies.

Three scientists recently reported their findings in the American journal Science. According to the study, the lemmings do show a regular change: the unusually crazy surge is followed by a rapid and drastic decrease. This phenomenon is not as simple as the “lemming mass suicide” says, “the truth is much more complicated”.

Scientists have found that the regular depletion of lemming rat populations is closely related to the “combinatorial action” of four predators: stoats, arctic foxes, snow owls and a seabird called the long-tailed skua. Lemmings look like voles and have always been the delicacy of these “four natural enemies”.

The number of close relatives such as lemmings and voles can suddenly increase to 100 or even 1000 times the normal number. The surge in lemmings has led to a surge in the number of various predators. The predators of lemmings are hungry and sometimes have such a delicious meal to enjoy, naturally “happy” to “try to add meals”, so the number is also amazingly increased, followed by more crazy predation of lemming, so that the near peak of the lemming population began to dramatically decline. Lemmings declined, predators could not continue to find enough food, and their numbers began to plummet. And so on, and so on.

In fact, the similar quantitative cycle between the “predator” and the “predator” in the biological chain in nature is all too familiar to biologists, and this cycle is a survival law for the biological population in nature to maintain “dynamic balance”. But interestingly, in the case of lemmings, this cycle of repetition seems to be on an alarm clock, and each time it is very punctual and stages a round of life and death battles.

Ferrets play a “key role”

Lemmings’ “boom-bust” cycles run a 4-year cycle. It is worth noting that in this cyclical chain, the stoat is a “key player”. Of the four predators, the stoat is the only predator that uses lemmings as a food source, and compared to the stoat’s “specialty”, the other three predators are “all-rounders”, they will “eat and eat” lemmings, but there are also some other food sources to choose from.

The almost “never-ending” daylight of the Greenland summer has greatly increased the amount of time scientists spend observing predators. The vast tundra of the Arctic also makes it relatively easy to observe and count lemmings. Scientists have observed that the tundra provides a large number of edible plants for lemmings, and the sand can easily dig holes and burrows. When the lemming population begins to increase, the number of stoats that feed on lemmings will also increase, and the stoat can be called the “expert” of preying lemmings. However, due to the super reproductive ability of lemmings, the growth rate of stoats is far less than that of lemmings, so the number of lemmings gradually exceeds the predatory ability of stoats, at this time, the other three predators will also join the predation team. It is said that a pair of snowy owls and their children can bring 50 pairs of lemmings back to their nests in a single day to enjoy.

Under the siege of the four major predators, the lemming population began to decrease significantly, and the number of stoats will also decrease accordingly. However, there was a time “delay” in the reduction process of stoats, and after about 1 year, the stoats experienced the “skin pain” caused by the reduction of lemmings, but it was too late, and the number of stoats that fed only lemmings began to decrease sharply. In the scientists’ statistics, the number of stoat populations became a key clue to a deep understanding of the lemming cycle. In contrast, the “all-rounders” are much more “calm” than the ferrets, and although they will also be affected, they can quickly shift their prey targets to other animals.

In the process of data analysis, according to the behavior pattern of “predators”, scientists have established a “predator-predator” analysis model, and the results can roughly calculate the “4-year cycle” of lemmings using various groups, which is basically consistent with the actual empirical data. The scientists said that during the observation, there was no indication that food sources and living space size would have an impact on lemming populations, so there was “no need to consider these two factors” in their model.

Gilger said: “Lemmings have a cyclical cycle, and for nearly a century this question has not been conclusive. This has become a very, very hot issue, and one of the most intensively studied problems in the field of population ecology. ”

Peter Hudson, a population ecologist at Pennsylvania State University, said cycles like lemmings also occur in large mammals such as birds, insects and bobcats. He praised the findings of three European scientists, calling it one of the few examples of nature reflecting the predictions of basic theories, and arguing that it would definitely be included in biology textbooks in the future.

lemming

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