question: Why do animals ''stop working'' sometimes and just freeze? Humans never seem to do that.
comment: Humans probably do it just as much as most animals. (Some animals do it more, with a specific evolved response of "playing dead".) I think the difference is that humans experience far fewer situations that would evoke an extreme response because we have altered the world so much. We are essentially always in the human world. But animals are often in very strange and unfamiliar situations caused by the human world. They don't know what to do, so they freeze. I should also note that for prey animals, like deer, crouching down in brush and freezing can be effective against predators. Humans freeze when things get extreme in our human world, like in instances of extreme violence or crime. If you read reports of what happens during mass shootings, people often freeze and don't flee, even as the shooter goes from one person to the next killing them. My coworker stopped an attempted rape (or rape in progress, I really don't know) in a public place where the woman didn't cry out or fight back. As he described it, she was totally frozen in fear and couldn't even respond with words until after the police arrived.
passages: In experiments on cats performed by Sutherland Simpson and Percy T. Herring, the animals were unable to survive when rectal temperature fell below 16 °C. At this low temperature, respiration became increasingly feeble; heart-impulse usually continued after respiration had ceased, the beats becoming very irregular, appearing to cease, then beginning again. Death appeared to be mainly due to asphyxia, and the only certain sign that it had taken place was the loss of knee-jerks.
   In the Inyo National Forest there are several records of large numbers of migrating mule deer falling to their deaths by slipping on ice while crossing mountain passes. This has occurred when heavy snowfalls have persisted until fall, and have been turned to ice by frequent thawing and freezing. In 2003 a rain-on-snow event encased the ground in ice, resulting in the starvation of 20,000 muskoxen on Banks Island in the Canadian Arctic.
  
  Saiga Antelope (2015)
   Winter rest in an animal is different from true hibernation, since the metabolism is not reduced drastically. The body temperature is not significantly lowered, however the heart rate is reduced. This means that animals like the raccoon can quickly become active again if temperatures rise or the snow melts. Other animals that winter rest are badgers and brown bears.
  
  Section::::See also.
  
  BULLET::::- Growing season
  
  BULLET::::- Cereal germ — the part of the cereal seed that grows into a plant
  
  BULLET::::- Seed dormancy
  
  BULLET::::- Stratification — the simulation of natural winter conditions for seeds
   Post-encounter defensive behaviours are avoidance behaviours performed when a predator is present and has been detected. When this stage of threat has been reached, behaviours are limited to species-specific defence reactions. These behaviours are commonly freezing, fleeing or threatening. The goal of a post-encounter defensive behaviour is to prevent the predatory imminence from further increasing. The dominant post-encounter defensive behaviour can depend on whether the predator has also detected the prey and how far away the two animals are from one another. Varying levels of predatory imminence, even in post-encounter situations, can affect the expressed defensive behaviour. If the prey has yet to be detected, the goal of the post-encounter behaviour will be to prevent the predator from detecting the prey. If both the predator and prey have detected each other, the goal will be to avoid making contact with the predator. Freezing behaviour in rats is an example of a post-encounter defensive behaviour which has been well studied. Freezing in rats is characterized by sudden, extended immobility, followed by a decreased heart rate and an increased respiration rate. This behaviour is often the dominant post-encounter defence behaviour in rats. In the laboratory setting, post-encounter defensive behaviours can be elicited by pairing a neutral stimulus, such as a light, with an aversive stimulus, such as a shock. The rat will engage in its post-encounter defensive behaviour when it becomes aware of the neutral stimulus, as the stimulus is acting as a predictor for the shock. Since the freezing behaviour is dominant in these situations, it can be assumed that it serves an adaptive function by preventing an additional increase in predatory imminence. Freezing is the dominant post-encounter behaviour because even when there are alternative defensive reactions available, freezing has been observed to be the rat's response the majority of the time. Even when a clear method of escape was made available, rats would freeze instead of fleeing. Freezing can prevent the perceived level of threat from increasing in several ways. If a rat becomes aware of a predator before the predator is aware of the prey, freezing can reduce the likelihood that the prey will be detected. As well, since many predators rely on motion to keep track of their prey, freezing may cause the predator to either lose site of their prey or shift their attention to a more active object.
   Freezing behavior or the freeze response is a reaction to specific stimuli, most commonly observed in prey animals. When a prey animal has been caught and completely overcome by the predator, it may respond by "freezing up" of in other words by staying complety still. Studies typically assess a conditioned freezing behavior response to stimuli that typically or innately do not cause fear, such as a tone or shock. Freezing behavior is most easily characterized by changes in blood pressure and lengths of time in crouching position, but it also is known to cause changes such as shortness of breath, increased heart rate, sweating, or choking sensation. However, since it is difficult to measure these sympathetic responses to fear stimuli, studies are typically confined to simple crouching times. A response to stimuli typically is said to be a "fight or flight", but is more completely described as "fight, flight, or freeze." In addition, freezing is observed to occur before or after a fight or flight response.
   Inactivity and starvation in mammals lead to atrophy of skeletal muscle, accompanied by a smaller number and size of the muscle cells as well as lower protein content. In humans, prolonged periods of immobilization, as in the cases of bed rest or astronauts flying in space, are known to result in muscle weakening and atrophy. Such consequences are also noted in small hibernating mammals like the golden-mantled ground squirrels and brown bats.
   In 2005, a baby dolphin (now named Winter) became entangled in the ropes of a crab trap. The rope cut off the supply of blood to her tail which resulted in her tail being amputated.
   BULLET::::- Many arctic birds and mammals can change their heat dissipation and metabolic rate in response to changes in temperature, as different populations of the same species display different averages depending on their current climate.
  
  BULLET::::- In arctic foxes ("Alopex lagopus)," starvation experiments indicate that the body mass in the arctic fox is regulated according to a seasonally changing set point and not by the availability of food. The basic metabolic rate varies seasonally being lower in winter than summer. The fur thickness can increase 140% from summer to winter.
  
  Section::::See also.
   Another study, conducted by Gisquet-Verrier et al., tested the effects of the hippocampus, in three experiments, on both the freezing behavior and avoidance. The rats were lesioned with ibotenic acid, and were tested against a control group. They first investigated changes from conditioned fear, and results showed that lesions to the hippocampus did not alter freezing behavior and marginally affected avoidance. Next, they tested single conditioning sessions, and it was found that freezing behavior remained unchanged while avoidance was disrupted. Finally, they tested conditioning with a larger stimulus (footshock intensity). It was found that avoidance was unaltered while freezing behavior decreased. Not only did these investigations show that the hippocampus is involved with freezing behavior, but avoidance and freezing behavior do not seem to have similar ways of being quantified when it comes to fear conditioning.
   To survive the harshness of winter, many animals have developed different behavioral and morphological adaptations for overwintering:
  
  BULLET::::- Migration is a common effect of winter upon animals, notably birds. However, the majority of birds do not migrate—the cardinal and European robin, for example. Some butterflies also migrate seasonally.
  
  BULLET::::- Hibernation is a state of reduced metabolic activity during the winter. Some animals "sleep" during winter and only come out when the warm weather returns; e.g., gophers, frogs, snakes, and bats.
   This family of the order Diprotodontia, which can be found in the east coast and inland of Australia and in some islands of New Guinea, is characterized by their very small size, which has side effects: because their mass-to-surface-area ratio is so small, heat escapes quicker from their bodies than it would in larger animals (the larger the mass-to-surface-area ratio, the harder it is to get rid of heat). Therefore, when temperature drops or food is scarce, they have trouble maintaining their body temperature and they enter a state known as torpidity (not to be confused with hibernation, which is not known in marsupials) which can last between one day and two weeks. In this state, the animal's breathing slows down, its temperature drops to almost that of its surroundings, and the animal becomes unresponsive.
   "Freezing" is when the dog stops abruptly and remains completely still, often looking out of the corner of his eye. This behavior is believed to have something to do with hunting behavior – when the prey is running, the dog attacks. Once the prey stops, the dog will stop too. We can often see this when dogs are chasing cats. This behavior, however, is used in several different situations. When you get angry and aggressive and appear threatening, the dog will often freeze and not move in order to help you calm down. Other times the dog may walk slowly, freeze, and then move slowly again. Very often a dog will stop and remain still when someone is approaching. Should a dog be in a conflict situation with a human or dog and is unable to escape, freezing may be one attempt to calm the other dog or person.
   Variability in discontinuous gas exchange cycles is also dependent upon external stimuli such as temperature and the partial pressure of O and CO in the external environment. Environmental stimuli may affect one or more aspects of discontinuous cycling, such as cycle frequency and the quantity of CO released at each burst. Temperature can have massive effects on the metabolic rate of ectothermic animals, and changes in metabolic rate can create large differences in discontinuous gas exchange cycles. At a species-specific low temperature discontinuous gas exchange cycles are known to cease entirely, as muscle function is lost and spiracles relax and open. The temperature at which muscular function is lost is known as the chill coma temperature.
   Quickly after the animal is incapacitated it is hung upside down by its hind limbs and an extremely sharp knife, in an orientation parallel to the ground, is fully inserted through the skin just behind the point of the jaw and below the neck bones. From this position, the knife is drawn forward away from the spine to sever the jugular veins, carotid arteries, and trachea. Properly performed, blood will flow freely and death will occur within seconds. Sheep and swine will reach brain death in under 10 seconds; however, larger animals, notably cattle may take up to 40 seconds to reach brain death. This period may extend to a couple of minutes if complications, such as arterial occlusion, occur. However, the animal's inverted position allows blood to flow more precipitously and thus makes an animal regaining consciousness before it is fully exsanguinated highly unlikely. In any case, animal welfare advisory councils clearly emphasize that the time from incapacitation to start of exsanguination should be prompt; recommending a time under 15 seconds.
   The primary focus of research for human hibernation is to reach a state of torpor, defined as a gradual physiological inhibition to reduce oxygen demand and obtain energy conservation by hypometabolic behaviors altering biochemical processes. In previous studies, it was demonstrated that physiological and biochemical events could inhibit endogenous thermoregulation before the onset of hypothermia in a challenging process known as "estivation." This is indispensable to survive harsh environmental conditions, as seen in some amphibians and reptiles.
  
  Section::::Scientific possibilities.
  
  Section::::Scientific possibilities.:Temperature-induced.
   I jumped into a seal hole, pushing the ice away as I entered, and they handed me my camera. Surprisingly, I wasn't too cold, except around where my mouth held on to my regulator, and that instantly froze and became numb. Suddenly everything was quiet and I found myself looking at easily one of the most extraordinary scenes I had ever, ever experienced. When I dropped down through a hole in the ice, I was completely surrounded by ice: a tunnel maybe twenty feet across. Everything above me on the land was roaring with wind and down there, there was absolutely no sound except for the distant trills of Weddell seals.
   Section::::Tonic immobility.:In chicken.
  
  See Chicken hypnotism.
  
  Section::::Tonic immobility.:In humans.
  
  Tonic immobility has been hypothesized to occur in humans undergoing intense trauma, including sexual assault. While "freezing" in response to life-threatening situations is well-known, the common "freeze" response exhibited by victims of rape is often misunderstood as passive consent.
  
  There is also an increasing body of evidence that points to a positive contribution of tonic immobility in human functioning. Thus, defensive immobilization is hypothesized to have played a crucial role in the evolution of human parent-child attachment, sustained attention and suggestibility, REM sleep and theory of mind.
   Methamphetamines have also shown that they could affect freezing behavior. Tsuchiya et al. conducted a study investigating the effect of methamphetamine pretreatment on freezing behavior. Rats were given the drug over a week, ramping up the doses. After that, there was a 5-day period without any drugs administered. The rats were then subjected to conditioned fear stress. Repeated but not single methamphetamine pretreatment resulted in a significantly increased freezing behavior. This evidence suggests that previous exposure to chronic methamphetamine results in an increased sensitivity to subsequent stress than a control group.
   During periods of cold, some ectotherms enter a state of torpor, in which their metabolism slows or, in some cases, such as the wood frog, effectively stops. The torpor might last overnight or last for a season, or even for years, depending on the species and circumstances.
  
  Section::::Pros and cons.
   Body temperature is not well regulated during REM sleep, and thus organisms become more sensitive to temperatures outside their thermoneutral zone. Cats and other small furry mammals will shiver and breathe faster to regulate temperature during NREMS but not during REMS. With the loss of muscle tone, animals lose the ability to regulate temperature through body movement. (However, even cats with pontine lesions preventing muscle atonia during REM did not regulate their temperature by shivering.) Neurons which typically activate in response to cold temperatures—triggers for neural thermoregulation—simply do not fire during REM sleep, as they do in NREM sleep and waking.
   Sleep is quickly reversible, as opposed to hibernation or coma, and sleep deprivation is followed by longer or deeper rebound sleep.
  
  Section::::Necessity.
  
  If sleep were not essential, one would expect to find:
  
  BULLET::::- Animal species that do not sleep at all
  
  BULLET::::- Animals that do not need recovery sleep after staying awake longer than usual
  
  BULLET::::- Animals that suffer no serious consequences as a result of lack of sleep
   Self-validating reduction applies beyond the human sphere as well. For example, wild animals who were not originally hostile or wary become that way upon being hunted. Scientific research on other animals that tends to avoid calling on their social instincts, in the name of objectivity, may in fact drive them away and actually induce an avoidance of humans that then is taken to be an objective and independent fact about them. Highly confined and managed animals under "factory farming" can be reduced to a state of social and physical dysfunction that seems to be their "inherent character", as Douglass puts it, thus making their treatment less morally troubling, and thereby making them more available for further reduction in turn.
   Freezing – or the complete halt of movement – has been documented in the family Sclerosomatidae. While this can mean an increased likelihood of immediate survival, it also leads to reduced food and water intake.
  
  Section::::Antipredator defenses.:Secondary defenses.:Bobbing.
   Supercooling is a last resort for animals. The best option is to move to a warmer environment if possible. As an animal gets farther and farther below its original freezing point the chance of spontaneous freezing increases dramatically for its internal fluids, as this is a thermodynamically unstable state. The fluids eventually reach the supercooling point, which is the temperature at which the supercooled solution freezes spontaneously due to being so far below its normal freezing point. Animals unintentionally undergo supercooling and are only able to decrease the odds of freezing once supercooled. Even though supercooling is essential for survival, there are many risks associated with it.
   Norwegian researchers at the University of Tromsø have shown that some Arctic animals (ptarmigan, reindeer) show circadian rhythms only in the parts of the year that have daily sunrises and sunsets. In one study of reindeer, animals at 70 degrees North showed circadian rhythms in the autumn, winter and spring, but not in the summer. Reindeer on Svalbard at 78 degrees North showed such rhythms only in autumn and spring. The researchers suspect that other Arctic animals as well may not show circadian rhythms in the constant light of summer and the constant dark of winter.
  
presuppositions: Humans don't "stop working" and freeze from cold. Humans don't stop working and freeze like animals do.
corrections: Humans would eventually stop and freeze in the cold but we have devloped enough of the world to prevent that from happening often.  Humans likely stop working and freeze just as much as animals do.
raw_presuppositions: Humans don't "stop working" and freeze from cold. Humans don't stop working and freeze like animals do.
raw_corrections: Humans would eventually stop and freeze in the cold but we have devloped enough of the world to prevent that from happening often.  Humans likely stop working and freeze just as much as animals do.