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 FREEZE TOLERANT VERTEBRATES

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These are some of the terrestrially-hibernating, freeze tolerant amphibians and reptiles that we work on in the Storey lab.
See pictures below

Amphibians

Reptiles

Wood frog (Rana sylvatica)

Painted turtles (Chrysemys picta)

Gray tree frog (Hyla versicolor)

Box turtles (Terrapene carolina)

Spring peeper (Pseudacris crucifer)

Garter snakes (Thamnophis sirtalis)

Chorus frog (Pseudacris triseriata)

European common lizard (Lacerta vivipara)

For cold-blooded terrestrial vertebrates, exposure to temperatures below 0C (32F) presents a serious problem because the freezing point of their blood is about -0.5C. Many animals avoid the risk of freezing by retreating underwater to hibernate (e.g. leopard frogs, bullfrogs, many turtles) or by going deep underground, either digging in by themselves (e.g. toads) or by using rodent tunnels or natural caves (e.g. salamanders, snakes).

But other amphibians and reptiles hibernate at or near the soil surface where temperatures can drop substantially below the freezing point of their body fluids. These have developed the amazing ability to endure the freezing of water in extracellular body compartments. As much as 65% of their total body water may be converted to ice and they can survive days or weeks of freezing.

Click to link to VIDEO, AUDIO and PRINT INTERVIEWS from the STOREY LAB and other popular information about frozen frogs

Click to link to go to scientific review articles and encyclopedia entries written by the STOREY LAB: both popular and detailed science

For an easy-to-read general article about Animal Cold Hardiness, also see PDF

 

COOL LINKS to other sites:

FROZEN ALIVE - pics and info on frozen frogs at NatureNorthZine

Wood frogs in the classroom and rearing tadpoles from NatureNorthZine

Frozen frogs at the San Francisco Exploratorium

 

LIFE STYLES OF THE COLD AND FROZEN - The Sciences magazine, 1999 Full Article

Frozen frogs in HISTORY, 1746-1849.

Frozen TURTLES: Out cold - The winter life of painted turtles. Natural History magazine, 1992 Full Article

 

 

 WOOD FROGS, Rana sylvatica

These are the best studied of all freeze tolerant vertebrates. Wood frogs breed very early in the spring in ephemeral forest ponds (see our favourite pond) and their eggs and tadpoles need to develop quickly before the ponds dry out. By hibernating on the forest floor, wood frogs can emerge with the melting snow and take immediate advantage of melt-water ponds for breeding. Wintering at the soil surface, the frogs gain significant insulation from blankets of leaf litter and snow but temperatures in their microhabitat still range down to -8C at times.

Picture 1 Wood frog

Picture 2 many color morphs

Picture 3 characteristic black mask

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Picture 4

Picture 5 juvenile, autumn of 1st year

Picture 6 bucket of frogs

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Picture 7 Frozen wood frog

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Picture 13

 

 

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As frogs freeze, they assume a crouched position with limbs drawn in close to the body and often digits tucked underneath. This position is known as the "water-holding" position and is used by all frogs when under desiccation stress. For frozen frogs this helps to reduce evaporative water loss from the body over what could be weeks of continuous freezing.

Frozen frogs have no heart beat, no blood circulation, no breathing, no detectable brain activity and cannot move yet miraculously all vital functions return within 1-2 hours when frogs thaw.

 

 

GRAY TREE FROG, Hyla versicolor

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These are intriguing fellows. They have the ability to change color, ranging from mottled gray through to lime green.

When frozen, they turn blue.

Picture 17 Frozen

 Picture 18

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 FREEZE TOLERANT REPTILES


Picture 19 Painted turtle hatchlings

Chrysemys picta

Picture 20 Western subspecies,
C. picta bellii with elaborate designs on the plastron
(from Turtle Mountain Park, Manitoba)

Picture 21 Midland subspecies,
C. picta marginata with less patterning on the plastron (from Algonquin Park, Ontario near the northern limit of the species range)

Although painted turtles hatch from their eggs in September, they do not leave their nests on lake and river banks until the next spring. To survive the winter, hatchlings have developed freeze tolerance. Adults have another remarkable ability -- they winter underwater and can survive for 3-4 months without breathing oxygen while in ice locked ponds. Link to our Anoxia Tolerance site.

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Picture 22 A-D

Painted turtles spend their first winter in the natal nest. They push out of their shells and sit in a heads up position. In the spring, they get active, dig out of the nest and head for the nearest body of water.

 

The sequence shows one hatchling exiting the nest. A couple of pieces of empty shell can also be seen.

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Picture 23 Garter snake

 

 

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Garter snakes winter underground, often massing by the hundreds in huge dens where temperatures rarely drop below 0C. Their tolerance to freezing is pretty minimal - up to a day at -1.5C but only a few hours at lower temperatures. However, this capacity might help them to survive unexpectedly cold nights in the spring or autumn. Alternately, detection of freezing within the den may stimulate them to move to warmer spots.

Read about Garter Snakes in the Classroom and the annual Narcisse snake log at NatureNorthZine.

Read more about the garter snakes on the U Haul website

 

Picture24 Box turtle

 

 

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Box turtles are the largest known freeze tolerant animal, ranging up to about 1 kg body weight. They hibernate in shallow burrows and probably don't encounter freezing conditions too often but we've documented survival after 2 days frozen at -2C.

 

Picture 25 European common lizard

 

 

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The European common lizard is one of the few Old World terrestrial species that hibernates where they receive significant subzero exposure. Lizards spend the winter about 2-4 cm beneath the vegetative litter in grass hummocks and their range extends into both alpine regions (1500 m) and above the Arctic circle.

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