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Rudolph
the red nosed reindeer didn’t start as a song or
even
a Rankin and Bass stop motion special. It was a story
published
by the Montgomery Ward Stores. The
author’s
brother-in-law
was Johnny Marks, the king of Christmas
songs.
He adapted the story into a song that was recorded
by
Gene Autry in 1949. Then it went viral. The TV
special
didn’t appear until 1964.
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This leads a biologist to ask, "Just who and what is
depending on the snow; how does snow affect the living world?" Many animals have
snow in their name, but that isn’t always a good clue. The snowy egret and the
snow crab are examples.
The snowy egret is called that only because of its white plumes,
while the snow crab is so named because its hunting season is when the snow is
the deepest. Mike Rowe, the hardest working man in show business since James
Brown, taught watchers of The Deadliest
Catch that the snow crab is better called the opilio crab (Chionoecetes opilio). Fisherman that go to
sea to put them on your table are a breed unto themselves.
Egrets and crabs don’t help us to investigate the question of the effects of snow on life. The easy observation is that snowy winters are
something that organisms have evolved to overcome or even use to their
advantage. They have developed ways to survive the harsh conditions of the
snowy season or to exploit the white stuff.
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The
snow leopard is unique amongst cats. It has blue-green or
gray
eyes, while most other cats have yellow or black eyes. It
also
can’t roar. It has a partially ossified (turned to bone)
hyoid
cartilage, which was thought to be the key to cat roars,
but
it just can’t manage more than a screech. Maybe it just
doesn’t feel like roaring – or maybe it fears an avalanche.
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On the other hand, their markings are better suited for
their preferred living and hunting grounds. They aren’t nearly as white as you
would expect. They like to live on rocky ledges and they descend into the
forests to hunt prey when the weather gets really cold (because that’s where
the prey are), so their brown tints and spots help them blend in to both
habitats.
The lemming is an example of a small mammal that exploits the
snow for cover, others being mice, voles, and shrews. The Norway lemming (Lemmus lemmus) moves from the low
mountainsides up to higher elevations (opposite of the snow leopard for obvious reasons) as the
snow falls. They don’t live underground, although they may nest there, but they
don’t live on top of the snow either.
The lemmings dig vast networks of tunnels in the snow where
it meets the ground. This is called the subnivean
environment (sub = below, and niveus is Latin for snow), and they race
around looking for vegetation to eat and other lemmings with which to mate. The
many openings in the snow may seem to be doors to the subnivean environment,
but the lemmings rarely come out of the snow. They are more likely vents to
release carbon dioxide from lemming breath and plant decomposition.
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Lemmings
don’t jump off cliffs in large numbers when they
get
older. That is a myth. However, they may be a little
challenged
when they run for new feeding grounds in great
numbers
– some seem to find their way to cliffs and accidently
go
over head first. They are solitary except for mating times,
as is seen here. He’s taking flowers to his girl.
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Some animals, like some big cats and large owls have evolved
a hearing sense that allows them to pinpoint lemmings under the snow, but the subnivean
tunnels work well enough that lemming populations usually skyrocket every 3-4
years, and then plummet as resources become scarce. Their success is in some ways their downfall.
And speaking of falling, the lemmings are also responsible
for some human tragedies. When the temperatures fluctuate and the tunnels
remodel with ice and snow, the layers of snow can become unstable. The dense
snow above the tunnel system will crush and slide off the subnivean layer and
…. look out below, here comes the avalanche. And I thought skiers that flock to
resorts in order to fall off the mountain repeatedly were the lemmings!
You wouldn’t expect it, but some small arthropods (insects
and such) have found ways to live in the snow. When a warmer winter day pops
up, so do the snow fleas (Hypogastrura nivicola). You will see them as black specks
on the snow – appearing in the thousands at the bases of trees. They aren’t
really fleas at all, but a species of springtail (see picture). The reason they
come out is not known exactly, but I think that any snow melt due to warmth might
drown them in their below ground hiding places.
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On
the left is a convention of snow fleas discussing the merits
of
elm leaves as decaying foliage – or maybe that’s the buffet.
On
the right is a single snow flea, called a springtail. The back
legs
can apply a load and then are released. They spring from
place to place, but they aren’t “fleaing.”
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Snow fleas have an antifreeze protein that keeps them alive
over the winter. This isn’t an exception, many animals have chemical
mechanisms to prevent freezing, but the protein in snow fleas is unlike any
other. The snow flea anti-freeze protein (sfAFP) may serve humans as well. See
the post here for more on anti-freezing mechanisms, and here to show that snow
midges are the largest animals in many parts of cold Antarctica.
A 2008 project produced the protein in a laboratory and
showed that it may be possible to use it to preserve organs for transplant a
longer time. Storage at cooler temperatures would allow for longer shelf lives
for organs, but they can become damaged by ice crystal formation. The
researchers also made a version of the protein using D-amino acids. We have
talked about these before – but here they work to our advantage, by making the
protein less susceptible to enzymatic degradation, while still providing
antifreeze function.
Snow melt mosquitoes, on the other hand, are winged. Living
from northern California up to the arctic tundra, snowpool Aedes mosquitoes
(many species) lay their eggs and their larvae develop in the pools of melted
snow as the weather warms. This gives them a head start on the rest of the
mosquito world. It would seem many forms of life have found ways to exploit
snow.
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Watermelon
snow is caused by an alga that grows in the
snow.
Chlamydomonas nivalis is a green
algae, but it also
produces
a lot of anthocyanins (red) pigments. They
absorb
the sunlight and generate heat. This melts some
of
the snow and gives the algae the water it needs to grow.
The
algae serves as a food source for other animals
during the winter, including the snow fleas.
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Then there are the chionophiles
(chioni is Greek for snow, and phile = lover). We have talked about the
psychrophiles, organisms that prefer cold temperatures, but chionophiles need the snow to survive.
It may seem counterintuitive, but many organisms need the
snow to keep them warm. It’s the wind that blows heat away from around the
skin, so a layer of snow actually helps trap heat and protect form the wind.
Lemmings give snow a big thumbs up (if they have thumbs) for snow as an
insulator.
It isn’t just animals that need a “blanket” of snow to
retain heat and protect from the wind. Winter wheat needs the snow, but for
several reasons. Sure, the snow provides insulation for the young shoots that
were planted in the late fall and go dormant until the spring. Nothing worse
than frozen wheat.
But the snow also provides a source of water when it melts.
This loosens the ground to give the wheat plants strength to push through the
earth, and for early water for growth. Snow also gives stability to the young
plants out on the plains. Lots of wind out there, enough to knock down and
break the fragile plants when they are young. A cast of snow surrounding the
stem helps keep them upright. The wise man says, “ Rain versus snow, the wheat
doesn’t know the difference, but the farmer wants snow in the winter.”
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Winter
wheat is susceptible to grey snow mold, even though
it
can produce antifungal compounds. This can decimate
entire
crops of wheat, especially if the snow fall lasts deep
into
the spring. The bottom image shows a close up of pink
snow
mold on grass. This is a particular problem on golf
courses
– I’m not going to cry over that.
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Snow mold doesn’t attack plants on exposed soil – but they
may be killed by the more extreme temperature. They do attack where there
is snow, and there is more damage in the deeper snow banks – it seems they do
their damage under cover of snow only – more snow, longer time for complete melt, more
damage.
The snow mold excretes its antifreeze proteins, not to
prevent itself from freezing, but to keep ice crystals from forming or
altering around the fungus. Perhaps they are protecting their food to keep
it growing and a good source of nutrients; often that food is wheat. But wheat
also has tricks. A 2002 study shows that winter wheat produces several proteins
that inhibit the growth of the mold.
Now back to Rudolph. To understand his exception with snow,
we first need to talk about photokeratitis
(photo = light, keratin = the protein found in cornea, and it is = inflammation), better known as snow blindness. For Eskimos and other humans, the 90% of the
sunlight’s UV waves bouncing off the snow is enough to burn the cornea and lead
to fuzzy vision or even blindness. The cornea is a protective structure,
keeping the UV rays from injuring the retina.
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This
is part of the study that discovered UV vision in
reindeer.
I get the part where they examine the retina,
but
what I need to know is how they get them to read
the lines of letters on the eye chart.
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Their cornea doesn’t stop UV rays from entering the eye, yet
they don’t suffer damage. The pigments of their retina absorb the energy and
convert it into images, just like our eye does with visible light only. A good
study would determine how they are protected – you work on that. It might be
related to a new study that shows that reindeer eyes change color with the
seasons, becoming blue in winter.
Being able to see in the UV range is what saves the reindeer.
Predators that blend in with the snow still show up easily in UV, and well as
urine stains in the snow that mark the territories of predators or other
reindeer. Using his UV vision, the reindeer is better protected from predation.
And it only works because of the snow – no snow, no reflected UV light. And
thus we learn…. snow saved Christmas.
Next week, the biology of one of the original Christmas gifts.
Next week, the biology of one of the original Christmas gifts.
For
more information or classroom activities, see:
A great book on the mechanisms of survival in the winter and how cold and snow affect life is entitled
Winter World, The Ingenuity of Animal Survival
Bernd Heinrich
2003
ecco publishing, an imprint of Harper-Collins
ISBN 0-06-019744-7
A great book on the mechanisms of survival in the winter and how cold and snow affect life is entitled
Winter World, The Ingenuity of Animal Survival
Bernd Heinrich
2003
ecco publishing, an imprint of Harper-Collins
ISBN 0-06-019744-7
Snow
blindness –
Reindeer
–
Subnivean
layer –
Winter
wheat –
Snow
mold –
Watermelon
snow -
