HibernationBy Laura Davis and Amy O’Malley

Preparation• Late summer and fall• Find location in which to safely hibernate– Areas not accessible by predators– Areas not likely to be subject to below freezing

temperatures• i.e. burrows, dens, caves

• Storage of food– In body as stored fat reserves

• Brown fat– Stored near them for easy access if they wake up

Toad

Dormouse

Hibernation• Drop in heart rate• Drop in body temp– 1 or 2 degrees above surrounding air

• Decrease in metabolism• Slowing of breathing– 3-5% lower oxygen consumption

• Food– Live off stored food reserves

• Body weight may drop as much as 50%– Awaken to eat stored food

True Hibernators

• A "True" hibernator appears to be dead • Some animals that you may think of as hibernators

actually enter a state or torpor.• TORPOR: a shortened sleep time. The heart rate slows

down and body temperature goes down, but the animal is able to wake up and move around

• BEARS are not "true" hibernators. – body temp drops a little and their heart rate slows down,

but not as much as true hibernators. Bears go into a "torpor" or temporary sleep and can wake up and walk around.

True hibernators: some bat species, dormouse (does not attract the attention of predators because its body temperature is so low that it gives off no body odor. Hibernates up to nine months), hedgehogDon’t hibernate: gray squirrel (active only briefly on cold days), Eurasian badger (lethargic during cold spells)

Hibernation Triggers• Differs from one group of animals to another• Environmental cues:– Scarcity of food– Seasonal changes in day length, or photoperiod– Temperature change– Circannual rhythm

• an internal biological rhythm with an approximately yearly cycle• ground squirrels have internal clocks that cause them to go into

hibernation at the usual time of year, even if they are kept in warm conditions with plenty of food.

• Not all known

HIT

• Hibernation Induction Trigger

– Chemical found in blood of several hibernating animals such as black bears

– Tested and proven to inhibit metabolic rates– Serves as a natural cellular protectant to maintain

cellular energy status and membrane integrity during hibernation.

Awakening• Scientists have hypothesized that animals may become sleep

deprived during hibernation and may wake up in intervals in order to catch up on sleep, which requires regular body temps

• Ectothermic animals may emerge from torpor when temperatures begin to rise, which raises their body temperature and metabolic rate

• Endothermic animals may use violent muscle contractions, or shivering to increase metabolism and heat production.– Requires an increase in oxygen consumption and heart

rate causing body temperature to rise.– The heart, brain, and other vital organs are the first to

warm up, followed by the outer extremities.

Hibernating Animals

• Non-mammals: species of lizards, frogs, toads, newts, snakes, turtles, and insects such as bees.

• Mammals: Chipmunks, ground squirrels, echidnas, possums,

• hedgehogs, hamsters, skunks, bats, prairie dogs, marmots, badgers, and some lemurs.

Cold BloodedPoikilotherms

• Amphibians and reptiles – Under decaying logs, deep protected rock crevices, burrows of

other animals• Snakes: congregate in deep caverns

– Usually groups of mixed species• Rattlesnakes, copperheads and northern black racers are frequently

found together in rock dens• Frogs and toads:

– Underground burrows– Some toads dig into soft soil with hind feet nearly 1 m deep.– Stream banks or pond bottoms– Cover of moss or leaf litter

Bats• Period of hibernation may be more than half a year. • Bats cluster in masses, usually in caves, old barns, and

other places that offer protection from the harshness of winter.

• They hang upside down and pull their wings and tails close to their bodies to keep warm.

• The core body temperature of some hibernating bats falls below freezing, as low as 23 Fahrenheit (-5 Celsius)in some cases, without harming them

• A hibernating bat's breathing rate falls from about 200 breaths per minute to between 25 and 30 a minute for three minutes, followed by an eight minute no-breathing break.

Squirrels/Chipmunks

• Not true hibernators• Wake up periodically (about once a week) for

12-20 hours– eat– secrete– Temperature increase

• Live off food reserves and stored fat

Bears• Not true hibernators- “sleep lightly”• Prepare in the summer by eating carbohydrate rich

food such as berries• Body temp drops by only 5-9°C• Heartbeat slows from 60-90bpm to 8-40bpm• Shelter-dens, caves, hollowed out trees– Fill with leaves and plant matter- insulation

• Head and body maintained at higher temperatures so they can react quickly

• Lose 15-40% of body weight• Females- In January, wake up long enough to give birth

Sources• http://content.answers.com/main/content/img/McGrawHill/

Encyclopedia/images/CE317700FG0010.gif• http://static.howstuffworks.com/gif/hibernation-dormouse.jpg• http://www.dragonhaven.plus.com/wildlife/toad%20hibernating.jpg• http://chestofbooks.com/health/natural-cure/The-Hygienic-System-

Fasting-and-Sun-Bathing/index.html• http://www.bio.davidson.edu/people/midorcas/animalphysiology/

websites/2000/Marks/lisa12.htm• http://www.wisegeek.com/which-animals-hibernate.htm• http://www.saskschools.ca/~gregory/winter/win2.html• http://encarta.msn.com/encnet/refpages/refarticle.aspx?

refid=761552980• http://www.saskschools.ca/~gregory/animals/amphibians/burrow.jpg