There is something about falling snowflakes that seems to blanket the ground with silence. Hushed are all of the noisy crickets and spring peepers that fill warmer nights with sound. We know that many birds and insects migrate south for the cold winter months, some mammals hibernate, humans are buttoned up indoors, but where is everyone else?
Reptiles have always been a mystery to me – how do heterothermic animals, without warm rocks or sun for basking, make it through to spring? Some of them will do the normal burrowing below the frost line to just barely avoid freezing temperatures. However, I recently learned in an article by Rick Lathrop (Rutgers University) that some reptiles, like Wood Frogs (Rana sylvatica) actually allow themselves to freeze when the temperature is low enough! Now this isn’t just reducing their body temperature by a few degrees - these are frog ice cubes we’re talking about! The usual problem with living cells freezing is that the expansion of the water will cause them to rupture, killing the cell. Rana sylvatica’s skin dehydrates first and then freezes. This cues the liver to send out sugars via the bloodstream to other parts of the frog’s body, acting as a sort of antifreeze and protecting its vital organs from damage. Wood frogs can go through waves of freezing and thawing throughout the winter, allowing up to 70% of their body to freeze for as long as a few weeks!
Thousands of years of natural selection and adaptation have given animals in North America a multitude of ways to survive cold winters. Sometimes, however, nature doesn’t cooperate. There has been a recent, and quite sad, occurrence in a member of the local ecosystem, which has rendered members of this species unable to survive the winter. Little brown bats, big brown bats, small-footed myotis, Eastern pipistrels and Indiana bats are the six species of bat that winter in New Jersey. These small mammals hibernate in habitats called hibernacula, created by abandoned mines, tunnels or caves (the largest being the Hibernia Mine in Rockaway Township, NJ). Unfortunately for these creatures, a cold-loving fungal disease called White Nose Syndrome has decimated their population by interrupting their hibernation cycles, a condition that was first noted in early 2007. Little understood but undergoing further research, White Nose Syndrome is believed to cause irritation to the bats’ snouts, waking them up from hibernation mid-winter, when there isn’t a sufficient insect population for them to feed on. (The photo below depicts some Little Brown Bats with White Nose Syndrome, and is by Al Hicks; New York Dept. of Environmental Conservation)
Reptiles have always been a mystery to me – how do heterothermic animals, without warm rocks or sun for basking, make it through to spring? Some of them will do the normal burrowing below the frost line to just barely avoid freezing temperatures. However, I recently learned in an article by Rick Lathrop (Rutgers University) that some reptiles, like Wood Frogs (Rana sylvatica) actually allow themselves to freeze when the temperature is low enough! Now this isn’t just reducing their body temperature by a few degrees - these are frog ice cubes we’re talking about! The usual problem with living cells freezing is that the expansion of the water will cause them to rupture, killing the cell. Rana sylvatica’s skin dehydrates first and then freezes. This cues the liver to send out sugars via the bloodstream to other parts of the frog’s body, acting as a sort of antifreeze and protecting its vital organs from damage. Wood frogs can go through waves of freezing and thawing throughout the winter, allowing up to 70% of their body to freeze for as long as a few weeks!
Thousands of years of natural selection and adaptation have given animals in North America a multitude of ways to survive cold winters. Sometimes, however, nature doesn’t cooperate. There has been a recent, and quite sad, occurrence in a member of the local ecosystem, which has rendered members of this species unable to survive the winter. Little brown bats, big brown bats, small-footed myotis, Eastern pipistrels and Indiana bats are the six species of bat that winter in New Jersey. These small mammals hibernate in habitats called hibernacula, created by abandoned mines, tunnels or caves (the largest being the Hibernia Mine in Rockaway Township, NJ). Unfortunately for these creatures, a cold-loving fungal disease called White Nose Syndrome has decimated their population by interrupting their hibernation cycles, a condition that was first noted in early 2007. Little understood but undergoing further research, White Nose Syndrome is believed to cause irritation to the bats’ snouts, waking them up from hibernation mid-winter, when there isn’t a sufficient insect population for them to feed on. (The photo below depicts some Little Brown Bats with White Nose Syndrome, and is by Al Hicks; New York Dept. of Environmental Conservation)
Even the animals that are active in the winter and have a consistent food source still have to make changes to survive the cold months. Many birds that winter in New Jersey, including Blue Birds, Dark Eyed Juncos, House Finches and Downy Woodpeckers, among others, have techniques to preserve body heat and find food when the temperatures drop. Black Capped Chickadees can be seen gathering and hiding seeds, berries and plant matter throughout the winter. They will hide each item in a different spot, and can remember thousands of hiding places. Since shivering can use up energy stored in fat reserves, Black Capped Chickadees will often enter a state of torpor, a short term reduction of body temperature and a slowing of the metabolism. They will go into torpor on the coldest winter nights, preserving their energy stores for foraging the next day. They usually will sleep in smaller tree cavities than they would in the summer, and will fluff up their feathers to insulate their bodies. When you see a ruffled looking Chickadee on your feeder in the morning, you’ll know that she was probably stuffed into a very small cavity with her feathers as puffed up as possible!
On cold winter nights I sure am glad to have a warm, comfy bed and electric heater, but you can sleep soundly knowing that the rest of the little creatures out there have methods of their own for keeping warm!
Here are some links to learn more about these winter survivors:
Black Capped Chickadee
http://www.allaboutbirds.org/guide/browse_tax.aspx?family=39
http://www.allaboutbirds.org/guide/browse_tax.aspx?family=39
NJ Bats and White Nose Syndrome
http://www.nwhc.usgs.gov/disease_information/white-nose_syndrome/
NY/NJ Trail Conference Trail Walker, Jan/Feb 2010 Edition
http://www.nynjtc.org/trailwalker/2010/jf10.pdf
http://www.nwhc.usgs.gov/disease_information/white-nose_syndrome/
NY/NJ Trail Conference Trail Walker, Jan/Feb 2010 Edition
http://www.nynjtc.org/trailwalker/2010/jf10.pdf
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