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Breaks in hibernation help fight bugs
August 17, 2006A habit in some animals to periodically wake up while hibernating may be an evolutionary mechanism to fight bacterial infection, according to researchers at Penn State. The finding could offer an insight into the spread and emergence of infectious disease in wildlife, and has potential implications for human health.
Many warm-blooded animals slip into an inert sleep-like state as part of a unique strategy to get past harsh winters when food supplies are low and the need for energy to stay warm is high. The immune system is in sleep mode as well.
"The production of antibodies, and white blood cells is stopped. Basically all cell reproduction shuts off," says Angela Luis, a doctoral candidate in ecology at Penn State's Center for Infectious Disease Dynamics.
However, animals regularly snap out of their torpor, and become fully active. But such sudden breaks from slumber eat into much of the animal's stored energy reserves, and it is not fully clear why the animals need to wake up, and how often
Some scientists think the answer lies in bacterial infections that could run rampant in the face of an immune system that is essentially asleep.
"Animals cannot tell when they need to wake up, or if they are infected," says Luis. If the animals hibernate for long they risk serious infection, she says, while waking up frequently wastes precious energy, and could prove fatal as well.
In other words, animals with an optimal time of torpor will win out over others, says Luis, who presented her findings at the 91st annual meeting of the Ecological Society of America.
Luis and her colleagues used a simple mathematical model that mimicked the growth of bacteria such as E. coli and Salmonella in European ground squirrels, and how it affected their torpor patterns in relation to temperature.
Microbial growth depends on temperature. Most bacteria grow faster when it is warm and much slower when it is cold. For animals exposed to Salmonella, which multiplies rapidly in warm temperature, a regular break in hibernation would be an important adaptation to combat the germs, when experiencing a warmer winter. However, Salmonella doesn't thrive at very low temperatures, so when animals experience a particularly cold winter, these breaks wouldn't be crucial.
But if the animals were exposed to certain pathogens that thrive at low temperatures, like some E. coli, the animals would still have to regularly break their hibernation to ensure protection at all temperatures, Luis explains.
"Our model, which is confirmed by field data, shows that torpor patterns generally seen in some hibernating animals may be an evolutionary adaptation to help protect them from bacteria that grow well in low temperatures," says Luis.
The researchers suggest that an understanding of how pathogens interact with their hibernating hosts could provide valuable insight into the spread and emergence of zoonotic diseases.
Penn State
However, animals regularly snap out of their torpor, and become fully active. But such sudden breaks from slumber eat into much of the animal's stored energy reserves, and it is not fully clear why the animals need to wake up, and how often
Some scientists think the answer lies in bacterial infections that could run rampant in the face of an immune system that is essentially asleep.
"Animals cannot tell when they need to wake up, or if they are infected," says Luis. If the animals hibernate for long they risk serious infection, she says, while waking up frequently wastes precious energy, and could prove fatal as well.
In other words, animals with an optimal time of torpor will win out over others, says Luis, who presented her findings at the 91st annual meeting of the Ecological Society of America.
Luis and her colleagues used a simple mathematical model that mimicked the growth of bacteria such as E. coli and Salmonella in European ground squirrels, and how it affected their torpor patterns in relation to temperature.
Microbial growth depends on temperature. Most bacteria grow faster when it is warm and much slower when it is cold. For animals exposed to Salmonella, which multiplies rapidly in warm temperature, a regular break in hibernation would be an important adaptation to combat the germs, when experiencing a warmer winter. However, Salmonella doesn't thrive at very low temperatures, so when animals experience a particularly cold winter, these breaks wouldn't be crucial.
But if the animals were exposed to certain pathogens that thrive at low temperatures, like some E. coli, the animals would still have to regularly break their hibernation to ensure protection at all temperatures, Luis explains.
"Our model, which is confirmed by field data, shows that torpor patterns generally seen in some hibernating animals may be an evolutionary adaptation to help protect them from bacteria that grow well in low temperatures," says Luis.
The researchers suggest that an understanding of how pathogens interact with their hibernating hosts could provide valuable insight into the spread and emergence of zoonotic diseases.
Penn State
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More Hibernation Current Events and Hibernation News Articles
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Hibernation (Patterns in Nature series) by Margaret Hall (Author) Simple text and photographs introduce hibernation and how some animals prepare for and experience hibernation each year. |
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What Is Hibernation? (Science of Living Things) by John Crossingham (Author), Bobbie Kalman (Author) This work is for ages 6-12. Hibernation is one of nature's greatest miracles, allowing animals to sleep through periods of extreme cold (and heat). From the tundra to the desert, this ability enables animals to live in some of Earth's harshest climates. Full-colour photographs and vivid text combine to give children a view of the many different ways that animals "sleep it off". Highlights include: how an animal's body uses fat to survive and even wake itself up; how an animal finds and prepares its den for hibernation; animals that estivate, or hibernate to escape heat; animals that give birth and care for their young during hibernation. |
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Time to Sleep (An Owlet Book) by Denise Fleming (Author), Denise Fleming (Illustrator) A warm, inviting bedtime book from a Caldecott winning illustrator. Bear sniffed once. She sniffed twice. "I smell winter in the air," said Bear. "It is time to crawl into my cave and sleep. But first I must tell Snail." Denise Fleming presents a warm-hearted story about animals of the forest settling down for their winter nap. But, like children who must go to bed for the night, they each find a way to put it off just a little bit longer. Richly illustrated in fall colors, Denise Fleming's story book world is right on target for preschoolers. |
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Hibernation (Cycles of Life) by Carolyn Scrace (Author), David Salariya (Author) Explains the process of hibernation, describing how a dormouse prepares for the long sleep. |
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Don't Wake Up the Bear! by Marjorie Dennis Murray (Author), Patricia Wittmann (Illustrator) On a cold, snowy evening, several animals snuggle up to a hibernating bear in order to keep warm. |
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Do Not Disturb: The Mysteries of Animal Hibernation and Sleep by Margery Facklam (Author), Pamela Johnson (Illustrator) |
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Animals in Winter (Let's-Read-and-Find-Out Science 1) by Henrietta Bancroft (Author), Helen K. Davie (Illustrator) Have you ever seen a butterfly in the snow? Probably not. Butterflies can't survive cold weather, so when winter comes, many butterflies fly to warmer places. They migrate. Woodchucks don't like cold weather either but they don't migrate; they hibernate. Woodchucks sleep in their dens all winter long. Read and find out how other animals cope with winter's worst weather. |
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How Do Bears Sleep (Carolrhoda Picture Books) by E. J. Bird (Author) Describes, in verse, what goes on in the bear's den during winter hibernation. |
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Party Decoration Necktie with eating, cone, squirrel, pine, food, hibernation by SHOPZEUS Party decoration necktie with sublimated artwork. High quality, silky touch, snow white polyester. Ideal birthday gift. Sublimation and shipping might take 6-10 business days. |
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