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A guided journey · 5 stops

The five ways of not being there

Hibernation, torpor, diapause and cryptobiosis were named by different fields studying different animals. Underneath, they are running much the same machinery.

The route

  1. Dormancy
  2. Torpor
  3. Diapause
  4. Cryptobiosis
  5. Tardigrade

A bad season can be survived, escaped, or slept through. This route is about the third option, and about the fact that it has been discovered independently five or six times and named differently each time.

Mammalogists named hibernation. Entomologists named diapause. A protozoologist named cryptobiosis. For most of a century these were treated as separate phenomena belonging to separate fields. Then somebody laid the metabolic measurements side by side, and a ground squirrel in winter, a moth pupa in August and a brine shrimp cyst turned out to be doing recognisably similar things.

The route starts with the shared machinery, because it makes the rest legible, then takes the two states that are genuinely different in kind — one that predicts rather than responds, and one that goes so deep nothing can be measured at all.

  1. Stop 1 of 5. Ecology

    Start with what all of them share

    The single most useful correction in this whole area is that a dormant animal is not a stopped animal. Metabolism falls further than the cooling alone can account for, which means something is actively holding it down — and the bear makes this unarguable, because its temperature barely moves while three-quarters of its metabolism disappears. Establish that here and none of the later pages can be misread as an animal simply going cold and slow.

    Read DormancyHibernation, torpor, aestivation, diapause and cryptobiosis were named by five different fields studying five different animals. Underneath, they are running much the same machinery.

  2. Stop 2 of 5. Behaviour and cognition

    Take the short version, and find out how it differs from the long one

    Most sources answer “what is the difference between torpor and hibernation” by asserting one. This page has a better answer: somebody compiled bout durations and minimum temperatures for more than two hundred species and looked at the shape of the distribution. It is bimodal. They are distinct states sharing a mechanism, and the boundary is measured rather than conventional — which is a more interesting answer than either “the same thing” or “unrelated”.

    Read TorporA hummingbird cannot survive a cold night at its normal metabolic rate, so it spends the night at twenty degrees cooler — deliberately, and reversibly by dawn.

  3. Stop 3 of 5. Insects

    Meet the one that is a prediction rather than a response

    Everything so far has been a reaction to conditions. Diapause is not. It is triggered by daylength — a cue that carries no hardship of its own — weeks before conditions worsen and sometimes a generation ahead, and an insect in diapause moved somewhere warm and well fed simply stays in diapause. That single fact separates it from every other state here, and it explains a decades-long apparent conflict in the literature that turned out to be about phases rather than about evidence.

    Read DiapauseAn insect entering diapause is not responding to winter. It is predicting it, from daylength, sometimes a generation before the winter arrives.

  4. Stop 4 of 5. Ecology

    Go to the deep end, and see where the evidence stops

    Cryptobiosis is where the measurements run out, and the page is as much about that as about the state. What is established is that no metabolism can be detected. What is not established is that none occurs, because you cannot measure the absence of something — you can only fail to find it. Keilin was careful about that in 1959 and every improvement in instrumentation since has left the careful version standing, which is itself informative.

    Read CryptobiosisIn the deepest dried states, no metabolism can be measured at all. Whether it has stopped or is merely below detection is still, honestly, unknown.

  5. Stop 5 of 5. Microorganisms

    End with the animal the superlatives are about

    The tardigrade is where this subject meets the public, and where the conditions get stripped off. The famous result is real: dried animals survived ten days of vacuum. The retellings dropped the drying, dropped the ten days, and dropped the fact that adding unfiltered sunlight killed nearly all of them. Ending here puts the whole route to work, because by now you have the machinery, the depth and the reason the conditions are the finding rather than the fine print.

    Read TardigradeIt survives the vacuum of space by turning into glass — and dies at the temperature of a warm bath when it is awake.

Where this leaves you

You end able to say what actually separates these states, which is more than most sources manage: not the animal, not the season, but the trigger, the depth and the duration. And you end with the two genuine oddities. Diapause is a prediction made before the hardship, on a cue carrying no information about it, and it cannot be undone by making conditions good. Cryptobiosis is a state where no metabolism can be detected at all — and where the honest claim stops at “cannot be detected”, because a negative result is bounded by the instrument.

What the route does not settle: whether cryptobiotic metabolism has genuinely stopped or is merely below detection, and why hibernators spend so much of their winter energy budget on repeatedly waking up.

Last reviewed 2026-09-03. All guided journeys