You probably learned in elementary school about how many mammals take a long “sleep” during the winter. But hibernation isn’t just a long sleep, but the changing of many different internal factors to conserve energy, and the animals isn’t usually unconscious the whole winter. Additionally, hibernation isn’t quite the same in all hibernating animals.
All animals require energy to perform every body function. This includes breathing, pumping blood, digesting food, and maintaining body temperature. When food is plentiful, most animals have no problem acquiring enough energy through food to drive all of these functions. In the winter, however, food is not plentiful enough for these animals to get enough food to drive their normal functions. By hibernating, animals go into a coma-like state in which their body functions perform less and require less energy. This means that their breathing slows, their heart rates slow down, they digest little to no food, and they allow their body temperatures to drop dramatically.
Up until 2011, scientists didn’t know very much about the hibernation of bears because of the dangers that would be involved in trying to monitor a bear’s bodily conditions. Scientists found that studying zoo bears wasn’t suitable because their internal cycles are disrupted when they are held in captivity. So scientists studied mostly small mammals because they would not be dangerous to hook up to measurement apparatuses.
However, in 2011,Oivind Toien of the University of Alaska Fairbanks acquired 5 black bears from the wild and surgically put sensors in them. They were then re-released into a protected area of woods where artificial dens were placed for them. They found that the black bears’ body temperature fell only to 85 degrees Fahrenheit, compared to smaller animals, whose temperature falls to borderline freezing during hibernation. Their metabolism also only fell to 25% of the normal function compared to smaller animals, which usually let their metabolisms fall to 2%. However, I have to wonder if any confounding third variables took part in this observational experiment, because the conditions were not exactly natural. Firstly, is there a possibility that the surgery and implementation of the monitoring devices could have interfered with the bears’ normal function? Could medication used on the bear for surgery have affected the bears’ internal functioning? Also, could the artificial den have made a difference in the bears’ conditions?
In addition, you may not have known that all hibernation does not happen during the winter. Some animals do a form of hibernating during the summer, called estivation. Many animals who estivate do so because they cannot survive in the intense heat, and burrow underground and enter a dormant state to stay cool. Some animals can also enter this coma-like state for less than a 24 hour period. This is called a daily torpor. The edible dormouse is actually capable of entering all three of these dormant states.
The edible dormouse can enter hibernation, estivation, or daily torpor.
Hopefully you’ve learned that hibernation is a bit more complicated and varied among animals than just a long sleep. Some animals hibernate more or less intensely, shorter or longer, or even at different times of the year and for different purposes.
Sources:
ScienceMadeSimple, How Stuff Works, Discover Magazine, TIME Magazine, NCBI
Your blog was well constructed and the questions you brought up regarding the effectiveness of the studies was a nice touch. I think you could add to your blog by expanding on the animals that hibernate during the summer and talk about any research that has been performed on them. Why would an animal only hibernate for 24 hours? You also mentioned how animals are not asleep for the whole duration of the winter months so you could have added what they do instead and whether or not their body temperature rises when they wake up for a brief time. Were there any other studies done that could back up your conclusion of what happens during hibernation?
I thought that this post was really interesting! I feel as though hibernation is extremely understudied. I liked how you asked multiple questions about the study and questioned its credibility. Since bears typically have a lot more fat than other animals, it seems reasonable that they would have a higher body temperature throughout hibernation. However, different bears live in different climates, and therefore, their fat levels differ. Something that would be interesting to look into would be the comparison of hibernation among different types of bears. Since studying polar bears and grizzly bears would be extremely dangerous and therefore next to impossible, finding evidence would be difficult. However, tranquilizers are extremely common and they could be used in order to sedate the bear long enough to insert a chip or another device into the bear. After releasing them back into the wild, the researchers would be able to track their hibernation patterns much more easily and safely. Overall, great post!
I learned about estivation, hibernation and torpor in environmental science my senior year and I found this to be a little more detailed. I agree with you about the possible confounding variables affecting the results of the testing of the black bears. But then it doesn’t surprise me that their body temperature would be higher than the smaller animals. Because the bears have more fat on them and overall more of them than the smaller animals, the bears would have a higher temperature. As far as metabolism, that still confuses me a little. I also found it interesting about the estivation and how in the summer some animals, like snakes go into their own hibernation because of the heat. What would happen if there wasn’t enough food for the bears during the non-winter seasons? Would it be a survival of the fittest/natural selection type thing? Or would the bear population decrease or go extinct?
Sorry about that last hyperlink not quite working. Hopefully it works this time: here is the correction on that last link .
This blog post is extremely kairotic- winter is fast approaching. Outside, we see as animals scramble to gather as much food as they can (squirrels, in specific), and while we cannot see them, we know other animals are doing the same elsewhere. It’s also kairotic in the sense that, while these animals prepare for hibernation…my roommate and I quite often prefer that daily torpor you mentioned during the weekends. (haha)
You did an excellent job explaining hibernation, which can quite often be complex, in a very simple, easy-to-read manner. In no way did you over-simplify. Rather, it was clear because of fluid writing and your thorough understanding. The organization of the blog only allowed for the increased clarity of your message.
Regarding the studies you mentioned; these certainly stood as powerful support and facts for your argument. What enhanced your message, and the focus of your blog mostly, was your thoughtful analysis of such studies. As for the surgery interfering with the bear’s normal function: I don’t think this is likely, but, as you stated, it’s definitely a possibility. To accurately address this possibility, I think you’d have to look at when this surgery was done. If it was weeks, or just a few months, before hibernation…it’s definitely possible. However, if it was much further than that, I’d say surgery being the culprit of any findings would be unlikely. Addressing the medication question, I think the answer is the same as it was for surgery. If it continued throughout hibernation, it could certainly alter the findings. If not, again, I’d say it’s unlikely. Concerning the artificial den: it’s hard to say. For the true answer to this, maybe one would have to examine different meta-analysis examples. What were other dens made of? What was this den made of? What were the structural and material differences? How much light entered the den? What was the average temperature? Questions like this should be examined further for more information.
Another question I have for the study: How was the information for the smaller animals studied/determined?
Overall, your blog post was good and really got me thinking more about hibernation. We hear the term used so often but seldomely really look into the inter-workings of the process. Some more information on how humans can hibernate (interesting, I know, and definitely appealing for us college students) can be found in this link, (a href=”http://www.livescience.com/33053-can-humans-hibernate-suspended-animation.html”> here)