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Thread: Hibernation

  1. #1 Hibernation 
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    If you observe a relative energy requirement chart, smaller animals require more energy than larger animals, and that smaller animals also have to use more energy for thermoregulation than larger organisms. Is that why you tend to see smaller organisms hibernating, as opposed to larger ones? I also believe I read that bears do not technically hibernate. So the rationale for smaller animals to hibernate, is to reduce their body temperature and save energy on thermoregulation, and to also reduce their metabolism and reduce some of the large energy requirement they have, being small animals?


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    No bears do not hibernate, there body temperature does not drop significantly and there heart rate doesn't change significantly, therefore its not considered hibernation. Bears and larger animals will go into deep prolonged sleep in order to avoid higher metabolism requiring activities during the winter. Raccoons, Badgers, Opossums do not hibernate either like bears.

    Smaller organisms, due to their body size cannot produce enough thermal insulation (for obvious reasons, because their fur cannot grow exceedingly where it would prohibit their movement). Thus, they are forced to either live in subnivean environment under the snow where the temperature doesn't drop below -5 C and/or have to enter a state of hibernation. These animals body temperature drops significantly, and their heart rate and breathing rate goes to as low as nearly 2 breaths and 5 heart beats per minute.


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    You could wake up a bear that's in a prolonged sleep state, however you won't be able to wake up a squirrel that's in hibernation. Unless ofcourse you bring that squirrel back to its regular non hibernating state body temperature. Hibernation is also a processes, it takes several steps to enter hibernation successfully.
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    Thanks for responding Andres I had an extended response question on my biology exam about torpor in hummingbirds, so I was in a way, checking to make sure my answer made sense.
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    Quote Originally Posted by Curiosity View Post
    Thanks for responding Andres I had an extended response question on my biology exam about torpor in hummingbirds, so I was in a way, checking to make sure my answer made sense.
    Lol, and since we both have aspirations in the field of Neuroscience. Did you know that body temperature is equally significant for neural networks? This is because temperature also regulates conduction velocity of our neurons. That's why its crucial we keep our body temperatures at around 37 C (humans).
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    By what mechanism does that work though?
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    Quote Originally Posted by Curiosity View Post
    By what mechanism does that work though?
    Temperature regulation or neural signaling conduction?
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    The effect of temperature on conduction velocity
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    Forum Junior AndresKiani's Avatar
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    Quote Originally Posted by Curiosity View Post
    The effect of temperature on conduction velocity
    Its like any other electrical circuit, conduction will be slowed by lower temperatures and increased by higher temperatures. In nerve cells depolarization and polarization of the ion channels is slowed by lower temperature. If you add more energy to an energy dependent system it will increase the rate of work. At lower temperatures, energy will flow from an energetic condition to less energetic condition, therefore you have less energy to carry out the amount of work that needs to be carried out.

    Another reason...

    We have to remember that the three states, depolarized, polarized, and hyperpolarized states of the nerve cell which allow the action potential to be self-propagated and fired through the cell. At lower temperatures, the electrochemical gradient will take longer to initiate depolarization due to less thermal energy and this will also cause an extended period of hyperpolarization after the signal has been fired from node to node.

    Also, remember that the axon is wrapped with layers of Myelin. This increases signal conductance by maintaining the full electrochemical energy within the axon, not allowing it the dissipate to the surrounding. Therefore nerve cells with a larger axon diameter due to Myelin sheath wrapping, have higher velocity conductance than those that have less. If the temperature is lowered, this allows for more dissipation of electrochemical energy during signaling, which results in slower conductance.
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    When you put an ice pack on a strained or injured area (muscle tissue or subdermal). This alleviates some of the pain by reducing the rate of conductance by those neurons that are firing signals to the brain to produce a pain sensation.
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    Quote Originally Posted by AndresKiani View Post
    Smaller organisms, due to their body size cannot produce enough thermal insulation (for obvious reasons, because their fur cannot grow exceedingly where it would prohibit their movement). Thus, they are forced to either live in subnivean environment under the snow where the temperature doesn't drop below -5 C and/or have to enter a state of hibernation. These animals body temperature drops significantly, and their heart rate and breathing rate goes to as low as nearly 2 breaths and 5 heart beats per minute.

    A better way of phrasing this would be to say that small mammals have a small large surface area to volume ratio. They radiate their internal body heat quite rapidly as a consequence. Also, hibernation is strongly linked to food availability - plants and insects are often not in abundance during the winter months.


    Edited the post, meant to say "large surface area", not "small surface area".
    Last edited by Zwirko; June 27th, 2014 at 09:23 AM.
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  13. #12  
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    Yeh that's exactly the case. I know in my answer on the exam I merely said that smaller organisms require greater energy expenditure for thermoregulation. I specifically remember the lecture addressing the topic of the question, not talking about surface area at all, because it was so obvious and almost didn't need to be stated.
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