Cirque de Squirrel

It's a good thing you know what squirrels look like, because I don't have a picture of a squirrel for you!  I wanted to write about them this week, but when I went to take pictures, they were gone for the day.  That's OK, though, because there is plenty of squirrel evidence visible in our outdoor classroom.  If you visit and don't see actual squirrels, look for clues instead.

Squirrels are messy eaters.  They unwrap their food, eat what's inside, then drop their food wrappers all over the place.  If you walk around the outdoor classroom and look down at the ground, you can see their food wrappers (complete with squirrel teeth marks) all over the place!  (You may notice that humans are also sometimes messy eaters - I picked up several human food wrappers out there this week.  Somehow human food wrappers are less adorable than squirrel-chewed walnut shells.)

Evidence of squirrels.

Another visible sign of squirrel activity is squirrel nests.  If you look to the top of the magnolia tree in the front yard of the beautiful building next to our classroom, you can see a squirrel nest.  Do you see it in the picture below?

Can you see the squirrel nest in the top of this tree?

Here is the squirrel nest a little closer:

Squirrel nest in the top of a magnolia tree.

Squirrels are probably the easiest topic for me to make interesting, because just about everything squirrels do is either hilarious, cute or annoying.  Here are a few fun things you might notice about them this time of year if you stop to watch them for a while.

1. Acrobatics.  Squirrels climb up and down all sorts of surfaces.  They are the only mammals that can climb down trees face-first, which they do by turning their back feet around as they descend.  Squirrels chase each other on mad dashes through the tree tops, often making great leaps from one tree to another like circus performers on a trapeze.  They also have a great high-wire act - squirrels commonly run across electric and telephone wires as easily as we run on sidewalks. 

2. Nest design.  Squirrels make extremely well-insulated nests in crevices in buildings or trees or constructed in tree branches or on top of bird nests.  They layer their nests with feathers or thistle or dandelion down (those feathery parts of the seeds).  When their nests are made of leaves, they can add layer after layer of leaves to make a hollow ball for sleeping.  The layers of leaves keep the rain out and the heat in.  Since squirrels don't hibernate, they need to keep their body temperature warm all winter, so their nests are important for keeping them warm at night, just like your nest, er, I mean, bed.  Look for squirrels carrying leaves or other materials to build nests next time you see one.  (You can try out a leaf nest for yourself.  If you layer about 50 tightly-packed leaves carefully over a balled-up paper towel then sprinkle water over the top, the paper towel is unlikely to get wet.)

3. Variety of Behaviors.  Squirrels are generalist feeders.  We always think of them as eating only nuts, but they also eat tree bark, berries and seeds.  Generalist feeders tend to have a much wider variety of behaviors than animals that eat only one thing.  Generalists must be curious about new food sources and adapt their food searching to a variety of challenges, which means their brains must be flexible and able to improvise.  Nothing against cows, but compare the variety of behaviors of squirrels to cows, and you can see what I mean.  Try making a list of all the things a squirrel does next time you see one.  I'll start: chase, dig, search in the grass, make a loud alarm call, climb up bricks.....

4. Problem Solving.  If you've ever had a squirrel figure out how to access the seeds in your bird feeder at home, you have seen the evidence of squirrels' ability to solve problems.  Once they locate a food source or nest site, they will try many new strategies to succeed in their plans to eat or build a nest.  Notice how ingenious this squirrel is at getting to what he wants despite human attempts to keep him out of the bird feeder.  Squirrels are an inspiring reminder to try many different strategies to succeed at a task.

5. Memory.  Squirrels have an unusually good memory for where they leave food.  They store food for the winter in a method called scatter-hoarding.  It's the opposite of how humans store food - all in one place in the kitchen pantry.  Squirrels leave little patches of food buried or hidden in hundreds of places, and they remember where they leave the food (they don't find their stashed food by smell - they find it by memory).  Scatter-hoarding is risky because squirrels can't guard all their food at once.  However, if their food is discovered and stolen from one location, they still have hundreds of backup locations that are unlikely to be raided.  Look for squirrels burying their food - the squirrel is almost 100% likely to come back and dig up that food later in the season. 

6. Deception.  I'm not condoning lying, but it sure is amusing to watch squirrels lie!  If a squirrel knows it is being watched by another squirrel, it will not actually hide its food.  Instead, it will pretend to hide the food by digging a hole, pretending to drop in a nut, and covering up the hole.  The watching competitor squirrel will be fooled, then the squirrel will go and hide the food in private so as not to reveal the hiding place.  It is easy to verify if a squirrel has lied.  Next time you see one bury a nut, go check and see if the squirrel has actually done so or if it has fooled you too.

Why Are There Cages of Meat in the Outdoor Classroom?

Note to lower-school teachers: please read this all the way through before you decide to share it with your students!  It was tough to figure out how many details to share for your audience.

Something is rotten in the State of Tennessee, and it just so happens to be right here in our outdoor classroom!  Unfortunately (or fortunately, depending on your perspective), the chance to see this first class example of rot will only be available for another few days.

Scientists will study anything.  And when I say anything, I mean ANYTHING!  Scientists know that even the strangest research topics can lead to useful discoveries.  For example, the discovery of new rainforest organisms can help lead to the development of new medicines, a protein discovered in jellyfish helps to grow better crop plants, and learning about the internal structures of spinach can help us build better solar panels.  The strangest details in nature can help humans change the world, so scientists study nature.  All of it.  Even when studying nature involves looking at dead organisms.  And that is why high school science students have left pieces of rotting meat in our outdoor classroom.

High school students studying rotting meat.

Decomposition (AKA rotting) is nature's way of recycling nutrients.  With no decomposition, we would have no new growth.  Decomposition is a familiar process, especially this time of year when leaves are piling up and rotting (if they are not raked up and removed).  Leaves decompose and break down where they fall, and if you don't rake them up, they will be mostly broken down into soil by spring.  Decomposed leaves return their nutrients into the soil, providing the nutrients for next year's growth.  In Middle Tennessee, we tend to have great soil because leaves from our trees decompose and add to the soil every fall.

High school student documenting the decomposition process.

Animals that die also decompose, just like plants.  Their nutrients are recycled into the soil and into organisms that use dead animals for food.  We are probably not as comfortable with the thought of animals decomposing because the sight of dead plants is so much more common than the sight of dead animals.  Also, the decomposition of animals can be a little smelly at times, since animals contain substances called nitrogen and sulfur, which are not present as much in plants.  Nitrogen and sulfur can turn into odorous compounds during decomposition (also noticed in the odor of urine (for nitrogen) and rotten eggs (for sulfur)).  But never fear - the smell isn't that bad, and it won't hurt you!  Go take a look to see what organisms are nature's recyclers of dead animals.

Animal-proof cage for decomposing meat, allowing decomposition to occur.

The high school science students have built two wire mesh test chambers for studying the organisms that decompose pork meat.  The wire mesh keeps out rats and vultures that might eat the meat before it can decompose.  The students placed the meat in the outdoor classroom last week, and they are now checking the meat daily and documenting what organisms they see on the meat (and you thought your homework was difficult!).  The teacher for their class tells me that the meat will be totally gone in a few days or up to a week and a half, depending on how warm the weather is.  The warmer the weather, the faster nature's recycling organisms will break down the meat.

Two tiny black ants summitted this mountain of meat, and beige-colored blowfly eggs coat the cut bone.

According to the high school teacher, there will be an enormous variety of organisms present on the meat over the next few days.  Mostly, there will be bacteria, which are microscopic organisms that live in and on the meat and break it down.  Bacteria will look like a white, beige or grey slime on the meat.  There will also be immature blowflies soon.  Blowflies look like metallic house flies, and they primarily lay their eggs in rotting meat.  The immature forms are called maggots, which look like fat, short, white worms.  In a day or two, you will be able to see maggots feeding on the meat (should you be so lucky).  Currently, there are a few ants on the meat.  The high school teacher tells me that ants usually show up later in the decomposition process, but I saw two ants that seem to have climbed to the top of the meat.  I thought they appeared to be very satisfied with themselves, standing on what must have been a mountain of food from their perspective!

If you wanted to investigate nature's recycling system for yourself, you could collect leaves or dead insects and monitor their decomposition in paper cups over a few weeks.  See what conditions are good for decomposition.  Is moist or dry better for rotting?  Will a dead insect decompose faster if it is sitting on moist soil or if it is alone in a dry cup?  Will dead leaves break down faster if they are open to the air or sealed into a cup with plastic wrap?  What about a leaf left whole versus a leaf torn into bits?  What leaves have decomposed more in our outdoor classroom - the ones in the pond or the ones laying around on the ground?  (See the leaf skeleton post for more on leaf decomposition.)