Snowflakes

Note: This piece first aired in January 2008

If you were paying attention to the immediate environment anywhere in Maine during December, you know it was covered with snow. That may be hard to remember during the current January thaw, but December 2007 was record setting for snowfall. Snow is frozen water, formed through a remarkably complex process in the clouds. We've talked about clouds before, they are formed when water vapor, the invisible gaseous form of water, condenses out of the air to form liquid water—that's what condensing is-going from gas to liquid. So clouds are masses of tiny drops of liquid water, suspended in the air. When the cloud gets cold enough, the droplets of water can freeze, forming the foundation for a snowflake. Then water vapor that is still in the air as gas freezes directly onto the ice nucleus—going directly from gas to solid—this process is called deposition-it's also the same process that causes freezer burn. So snow isn't frozen rain—that does occur but we call it sleet—solid ice pellets that form when rain falls through a cold air layer on its way down to the ground. Snow is the direct deposition of ice crystals onto an ice nucleus, and the shapes and forms it takes are highly dependent on both the temperature and the relative humidity of the air where the snowflake originates.

We've all heard the saying that no two snowflakes are alike, which is really neither here nor there, as it would be impossible to prove or disprove anyway. What is certain, and easily observable for most of us, is that snowflakes come in several distinct shapes. Almost all snowflakes have some sort of 6 sided or hexagonal structure. This comes from the way the water molecules arrange themselves when they freeze and form crystals, due in large part to the unique qualities of the water molecule. But that's another story.

When it is very cold, the air does not hold much water vapor, and the snow that forms tends to come in very small, simple shapes, plates-flat hexagons, or small columns (like a stack of plate snowflakes). As the air warms up more complex forms show up, stellars—which are star shaped, and dendrites—which are lacy or leafy—the classic snow flake we all imagine. Snowflakes also come in the form of needles! Any of these forms can show secondary effects as well, like when the snow flake falls or gets recirculated through a higher humidity cloud or fog. When it makes it down to the ground it looks like little bits of Styrofoam and is called graupel.

So you have an assignment. The next time it snows, go outside with a dark jacket on. Catch some falling snow flakes on your arm and look closely at them. See if you can determine their general form. Don't be discouraged if you can't tell at first, when its windy snowflakes get broken up on the way down, and it its warm they stick together. You will probably be able to identify parts, and if it's a nice calm snow event, you should be able to see snowflakes in their entirety.

Barred Owls

Earlier this winter I was standing in the drive way chatting with my neighbor when an owl swooped down out from the trees near by and landed on a fence post in my neighbor’s yard. Apparently my neighbor was feeding some resident red squirrels, who had made their home in the covered patio furniture directly under the fence post where the owl was now sitting, so there was no mystery about what he or she was after.

The owl turned out to be a barred owl, Strix varia in the scientific nomenclature. Barred owls are quite common in Maine, they are certainly the ones I hear vocalizing the most. They are permanent residents of the state, meaning they do not migrate. They are generally permanent residents of their breeding grounds as well, so if you have barred owls around your house it is likely that they will remain. Most owls are active at night, called nocturnal, or during dusk and dawn, called crepuscular. The barred owl is active during all of these times, but may also be active during the day, especially if it is an overcast gray day, as it was the day I saw one on the fence post.

The barred owl is exquisitely adapted to do what it does, which is hunt silently and effectively, preying on small rodents and other animals. All animals have adaptations that allow them to fill their niches, some more so than others. On one end of the spectrum are animals (and plants too for that matter) that are rather cosmopolitan , with very general adaptations that allow them to function and even thrive in a wide variety of conditions and use diverse food sources. Humans, rats, and sea gulls are examples of these wide ranging species. On the other end of the spectrum are plants and animals with very specific or narrow niches—basically they are highly specialized to eat a certain food, be pollinated by just one specific pollinator, or live a certain way. Owls, though they can eat a relatively wide variety of foods, are generally thought to be on the highly specialized end of the spectrum.

The barred owl in my neighborhood, like barred owls all over Maine have their eyes on the front of their faces, like humans. Most other birds have eyes on the sides of their heads. The forward facing eyes do the same thing for owls that they do for us, that is give us excellent depth perception. This helps them hunt during low light conditions. Their ears are also specially adapted to help them hunt after dark. The ears of the barred owl are asymmetric. They have one on each side of their head, like we do, but they are not at the same level, one is higher than the other. This asymmetry helps them pinpoint the location of sounds. Barred owls tend to know their territory very well, so between their good depth perception, their acute hearing and their mental map of every perch in their hunting grounds, they are successful and opportunistic predators.

Pay attention in the next couple of months, Barred owls will be mating, which usually means a lot of vocalization. You may hear their familiar “who cooks for you?” call, or even something that sounds like a pack of monkeys has arrived in the Maine woods. Either way, its more likely that you will hear an owl than see one.

First Aired January 2008

Snowshoe Hares

One of my favorite things about walking in the woods during Maine winter is seeing animal tracks in the snow. Deer, red squirrel, turkey and probably most reliably snow shoe hare. Snow shoe hares are common throughout northern north America, though their numbers can varied wildly from year to year as a result of predation pressure. If you want to see their tracks look in the snow anywhere in the woods there is dense underbrush or stands of conifers. Swampy alder thickets, boggy areas, these are great places to look for snowshoe hare tracks.

Snow shoe hares get their name from their big back feet—large in surface area, and covered with dense fur, they act like snow shoes and allow the hare to move around easily on the snow pack. They are also called varying hares—this name comes from the fact that they change color seasonally. In the winter the snow shoe hare is white, and in the summer it is brown to reddish brown. This is an adaptation to help them avoid their nearly inevitable fate—snow shoe hare are the all you can eat buffet of the northern forest. Essentially their job is to get eaten. They can live up to 5 years, but one study suggests that 85% of them make it barely a year—and this is what is described in the literature as being very good at avoiding predation. Clearly if they were any worse there wouldn’t be any left. But back to this seasonal color change. In the summer they have a thin brownish coat, they blend in well with their underbrush habitat. The change to white is controlled by photoperiod, or length of day. As the days start to shorten in the fall, the hare’s body senses it and responds by turning on a second set of hair follicles-the cells that grow hair and fur, this second set is the one that grow the thick white winter coat. The summer hair follicles, the ones that grown the summer coat, stop making brown hair, and the summer coat molts out and isn’t replaced. This transformation can take up to 10 weeks. And it reverses in the spring when the days get longer again. It is a great strategy when the timing is right, and the white coat coincides with the snow fall, and the brown coat coincides with the spring melt. When the snow is late, or early, or melts early, or hangs around late, the hare’s cammoflage can be compromised.

Today is a double whammy when it comes to cool facts. Because not only does the snowshoe hare experience a seasonal color change that is controlled by day length, they also engage in coprophagy. And what is this you may ask. Quite simply it means they eat their own dung. Yes, you heard me right. It turns out that what hares eat is relatively hard to digest. Grass, twigs, bark, buds, all things that are full of cellulose and other difficult to break down organic compounds that do not readily give up their nutrients. The bacteria that live in the hare’s gut work away at digesting this material, but it takes a long time, longer than this material actually can stay inside the hare. So the hare goes to all the trouble to forage, but can’t fully digest the material it eats, thus it does a lot of work for not so much nutrition. The way it solves this problem is, you guessed it, after the first pass through the digestive track the hare eats its own fecal material, and gives its intestinal bacteria a second chance to liberate all possible nutrition from the hard to digest fodder.

There are lots of animals I would love to be even if just for a little while, but between constant pressure of everyone trying to eat me, and having to survive by eating my own poo, I am glad I’ll probably never get to be a snowshoe hare.