Resin, Pitch, Sap

by Holly Schubert

While walking in the forests at Lutherlyn and other places, we have occasionally noticed a sticky substance oozing out of trees, usually evergreen trees. Maybe you've seen it too, and if you've played in pine or spruce trees as a kid, maybe you've gotten this sticky goop on your hands, clothes, or even in your hair (yuck). I've wondered, and maybe you have too: what exactly is that stuff? (And for me, when I find something new in nature, another question that usually follows closely behind that is "can I eat it?" Or in general "how can I use it?")

Sap 

Many people assume that this sticky substance is sap, because it oozes out of trees. It is not sap. Sap is made up mostly of water, and carries water and minerals from the roots to the leaves through the sapwood (xylem) of a tree and carries water, sugar, and other nutrients from the leaves to the rest of the tree through the inner bark (phloem). Sap "runs" in sapwood when temperatures vary between above freezing during the day and below freezing at night. The temperature variation causes a difference in pressure inside the plant tissues, which pushes the sap up the sapwood during the day, and allows it to drop back to the roots at night. (This is when we can gather maple sap to produce syrup.)    

Resin 

The sticky stuff we see on evergreen trees (and some other plants) is not sap, or even hardened or thickened sap. It is a different substance altogether, called resin. The US Forest Service tells us that "resins are plant products that, 

• are not soluble in water, 
• harden when exposed to air, 
• do not play a role in the fundamental processes of the plant, and 
• are generally produced by woody plants.  

buck rub and resin flow on young norway spruce tree,
Venango Trail at Camp Lutherlyn

Resins are produced in special resin cells in plants, and are also produced when an injury occurs to the plant. Resins can be produced through the bark of a tree, the flowers of an herb, or the buds of a shrub." 

While resins do not "play a role in the fundamental processes of the plant" and are usually considered a waste product of cellular processes in the plant, they do provide a number of benefits to the plants that produce them. Resins seal over wounds, decrease water loss, protect from pests, and have antimicrobial properties that help prevent decay and infections.

Resins have also proven to be useful to humans. People have gathered and used resins from plants for thousands of years. Resins have been used for waterproofing, varnishes, adhesives, art, incense, medicines, food, and many other purposes. Some famous resins include  frankincense, myrrh, balm of Gilead, amber, and balsam. Some products that have been made from resins include pine tar, pitch, rosin, and turpentine, though some of these are now made synthetically or from petroleum products instead of plant resins.  

Amber is a fossilized resin. Though it is not a mineral, it has an appearance similar to a gemstone, and is often used for jewelry. Amber is created when resin hardens and then becomes trapped in layers of soil, which blocks off the oxygen that would cause it to decay. As the volatile oils in the resin slowly permeate out over millions of years, the resin becomes preserved, and turns to amber. Ambers have been found that are from 30 to 125 million years old! Occasionally, plant and animal matter that was trapped in the resin that became amber is also preserved, inside the amber. These inclusions can be used to extract DNA and study the flora and fauna of the distant past (as in the famous plot premise of the movie Jurassic Park). The resins that produced amber came from tree species that no longer exist today, but are most closely related to today's conifers, including pines.

All of the conifers common in Pennsylvania produce resins. Of the trees growing in our area, spruces, Scots pine, and larch have historically been used to produce products like turpentine from resin. At Lutherly, Norway spruce seems to produce the most resin, followed by white pine, and then other evergreens. In the northern woodlands that cover the upper reaches of the northeastern United States, balsam fir produces the most renowned resin. The resin is present in blister-like pockets that cover the bark, and its high oil content makes it simultaneously flammable, edible, and medicinal (though I imagine you might have to develop a taste for the flavor).

Some animals even use resin. One of the substances honey bees create in their hives is propolis. This sticky "bee-glue" is used to fill small cracks in the hive, smooth surfaces, and even seal off sources of contamination in the hive and keep the hive healthy. It is made from resins gathered from plants such as poplars and conifers, and mixed with saliva and wax. Propolis has also been used by humans for everything from embalming to antibiotics.  

Rosin is another product made from resin, used in fields from music to sports to industry. Musicians add it to the bow hairs of stringed musical instruments like violins; dancers, gymnasts, rock climbers and baseball players add it to shoes and hands to improve grip; and many industrial processes use it to create the right consistency in products ranging from chewing gum to lead soldering.  

Pitch 

People sometimes seem to use the word pitch to refer to the same substance as resin - that sticky stuff coming out of the trees. (I grew up calling it "pine pitch.") Or, in common usage it sometimes refers to the more fluid state of this substance, while resin is assumed to have hardened. But more properly, pitch refers to a product made from resin. Heating resin and mixing in a fiber and possibly a wax creates pitch, which is useful as an adhesive, waterproofing layer, or flammable material for firestarter, torches and crude candles. This is the type of pitch that native Americans used to waterproof the seams of birchbark canoes. 

Pitch can be produced from wood by heating the wood without burning it, which causes the pitch and tar to ooze out of the wood and leaves behind charcoal. (Pitch and tar are similar substances, but pitch is thicker and tar is more fluid.) Pitch was traditionally used to waterproof the seams of wooden sailing vessels, buckets, and barrels. The biggest producers of this type of pitch in the 1600's through early 1900's were Scandinavian countries and the North American colonies that later became the United States. 
At the same time, pitch is also a more general term for a number of "viscoelastic solid polymers." This means that even though it seems to be solid at room temperature and can be shattered with a hard impact, it is actually fluid and will flow over time, but extremely slowly. In this general sense, pitch can be natural or manufactured, from petroleum products or plants.

Naturally occurring asphalt or bitumen, a viscous semi-solid form of petroleum, is a type of pitch that has been used in "pitch drop experiments" to study and demonstrate the flow of a seemingly solid material over a period of many years. The University of Queensland in Australia and Trinity College in Ireland have both observed pitch over many decades, recording only nine  "drips" of the pitch in the course of their observations. In 2013 scientists at Trinity College were able to record pitch dripping from a funnel on camera for the first time. 

We still say something is "pitch-black" if it is very dark, because whether it is made from trees or petroleum, pitch is very dark in color.

 Gummosis

We have also noticed blobs of a gummy substance on wild black cherry trees, as well as cultivated cherry and peach trees. It is often mostly clear, or a little bit amber in color, and feels rubbery but not as sticky as the resin found on evergreens. I was surprised to discover that unlike the resin on evergreens, this IS a result of sap flowing out of trees. It is fairly common in "stone fruit" trees like cherries and peaches, and is referred to as gummosis. Sap from the tree oozes out of wounds in the bark caused by insects, fungus, or broken branches, and as it dries creates the gummosis. It is sometimes an indication that the tree is unhealthy because it is being attacked by insects or disease, but is sometimes simply the result of cracks in the bark or branches caused by wind or other damage.

It is amazing that the simple sticky blobs we see on trees are connected to so much history and fascinating information! For more reading about some of the topics mentioned, check out the links below. 

US Forest Service on resin

http://www.fs.fed.us/wildflowers/ethnobotany/resins.shtml

Temperate Climate Permaculture on resin (including biology, history and human use)

http://tcpermaculture.com/site/2014/08/04/tapping-the-pine-tree-plant-resins-and-their-uses/

Balsam fir, and resins in general

http://northernwoodlands.org/articles/article/blisters

Creation of amber from resin:

https://www.amberjewelry.com/Amber-Frozen-Moments-in-Time-s/97.htm

http://academic.emporia.edu/abersusa/whatis.htm

Propolis

http://basicbeekeeping.blogspot.com/2011/12/lesson-113-sticky-subject-of-propolis.html

Pitch

https://en.wikipedia.org/wiki/Pitch_(resin)

Historical production of pitch

http://www.maritime.org/conf/conf-kaye-tar.htm

Gummosis

http://www.missouribotanicalgarden.org/gardens-gardening/your-garden/help-for-the-home-gardener/advice-tips-resources/pests-and-problems/diseases/cankers/gummosis-of-fruit-trees.aspx

Good Neighbors Help Each Other Out

by Holly Schubert



Last spring, I got to have an up-close-and-personal encounter with some of the wildlife of Lutherlyn in the garden shed at Terra Dei.  

A few times when I went into the shed, I had noticed some items on the floor of the shed, when I thought I had left them on the shelves. I chalked it up to my own carelessness and put them back on the shelf, but found them on the floor again not long after. I wondered if some critters were to blame...  

Not long after that, I posted this to my facebook page:  

  

May 22, 2015 

I found out who has been knocking things off the shelves in the garden shed. Look closely - not everything that looks like a hose is a hose!  

Snakes among hoses

What appeared to be two black rat snakes had taken up residence in the corner of the shed. I had only seen one head, but traced the length of the bodies down to two tails. I was pretty sure there were two large snakes, one with its head buried in the hoses and other garden equipment piled in the corner. It seemed to really like being entwined through the openings of a plastic crate.  

Though it made my heart pound a bit to see them in such close quarters (and getting planting trays out of the corner of the shelf was a delicate procedure!), I thought they were pretty cool and liked having them as neighbors.  

Snake on a rake.

Since we garden organically at Terra Dei, we rely on natural means for controlling pests. Often this means encouraging predators to live near the gardens who will eat the pests. Black rat snakes are great for controlling small rodents like mice and voles which might eat our garden veggies before we have a chance to. We like having snakes around! They especially like to hang out in the large compost piles next to the garden, where the black plastic covering and the heat from the decaying matter makes for a nice warm nest.  

Large compost bins where the snakes like to hang out.

About a week later, I saw that one of the snakes was poking its head out of a pile of blueberry netting that had been wadded up in the plastic crate. (You can see the pile of netting in the picture of the emptied shelves above, it's the black tangle of stuff just below the rake in the left of the picture.) In the next day or two, I noticed this snake seemed to be in the same place every time I came into the shed, and wondered if it was stuck in the netting.  

Since I hadn’t seen it move in a day or two, I decided to try to pull out the netting out of the corner to see if the snake was stuck or not. When I did, I got a surprise! THREE snakes! All of them very very stuck in the netting.

One head, three tails. The head that is circled in red is the first one I noticed

poking out of the netting, and my first indication that the snakes might be stuck. 

I later learned that it is very common for snakes to get caught in netting like this. The openings in the netting are very small, less than an inch square. The snakes go forward through the openings with their narrow head, then get to a point where their bodies are too large to go any further. But then, they are in too tight to back out, because their scales catch on the netting. The netting is made of plastic that doesn't stretch or break easily and will not biodegrade for a long time, so once they are in it, the snakes are totally stuck. 

I hated the thought of the snakes caught like this. The netting was pretty tight around their bodies, and I was afraid it was hurting them. As I mentioned, we want the snakes around the garden because they are helpful; and also, I had become attached to my new neighbors over the last week or so, and I didn’t want these “friends” of mine to suffer. So I decided to try to cut the netting away from the snakes to free them.  

The snakes were held so tightly by the netting that they were unable to move their heads at all, which made it easier for me to get close enough to cut away some of the netting. I reached out at arms-length and started snipping to try and loosen the knotted tangle of netting. I made some progress. However, as I cut away more netting, the snake’s bodies were freer and they were able to move more, which made me more uncomfortable with getting close enough to their bodies to cut the parts that needed to come away to free them.

In the picture above, and in the one marked below, you can see one whole snake tail-to-head from the bottom left to top right of the pic. (This is the smallest of the three.) Another has its head leaning on the end of the broom, and its body is curled up near the snake on the right. A third head is completely entangled just down and to the left of the head in the top right. The body that reaches into the corner of the shed at the top of the picture belongs to that head.

This is about as far as I got in my attempts to free them on my own, tentatively leaning in and snipping at arms length! 

It was time for a break to get some dinner and enlist some help!

I called our friend April Claus from Fern Hollow Nature Center, who is a herpetologist and specializes in salamanders and snakes.  

It was April who told me that this situation is very common - she said she rescues snakes stuck like this all the time. She suggested I find someone to hold the head of the snake in a thick towel, while I cut the netting out from around the snake’s body to free it.  

I got in touch with Chris Piatt, our amazing environmental education intern for the spring, who was living onsite (and therefore was around even though it was Friday at dinnertime) and who I knew to be sympathetic to snakes. He agreed to come to the garden after dinner and help me out.  

Snake pile and water dishes. Giving water dishes to snakes in my shed and
trying to get them to drink is one of the stranger things I've ever done!

I had learned from April that the snakes would probably be very dehydrated, from being stuck in place and from struggling to get free, and I should try to give them water. So while I waited for Chris to arrive, I put out water for the snakes and tried to get them to drink. (I soon realized the best way for them to drink water was straight from the floor.)    

The snake in the right of the picture is thirstily slurping water off the floor.

Chris to the rescue! Snake selfie. Snelfie?

When Chris arrived he put on gloves, started talking soothingly to the snakes, and with slow, gentle, careful movements, got right up next to the snakes and started cutting the pieces of netting around their bodies. He held them gently with one hand and cut with the other. 

Look how tangled this poor guy is in the front of the picture. The netting was so tight around their bodies and necks. 

They were very docile and didn’t snap or display any aggression. Occasionally they would start twining their tails around, sometimes wrapping around tools and other things in the shed. When they would do this, I would hold the tail ends of the snakes (sometimes in a bucket!) to keep them from moving too much or getting tangled in a way that would make things harder. It was amazing to feel their strong smooth muscles working, and to safely be in such close contact with such beautiful wild creatures.  

Snake #1 is free.

It was slow meticulous work but eventually, snake #1 was free! Moments later it slithered away into the tall weeds. Happy moment! 

A little while later, snake #2 was free!  

When I talked with April she had explained to me that the three snakes were probably gathering in the shed to mate. The female (probably the largest of the three) would have arrived first and released a scent to attract the males. When two males responded, the female would choose one of them to mate with. Snakes #1 and #2 were probably the males vying to mate with the female. 

Snake #2 is free. You can see it's already getting dark out.

It was 9:30 by the time we got snake #3 free, the largest, and probably the female. It was getting dark so we moved closer to the house so we could use the outside lights to help us see. Again, I got to hold the tail as Chris worked at loosening the netting around her head. She was so strong and beautiful!

We were nearly ready to let her go when we realized that there was a final piece of netting tangled near the snake’s face. It appeared to be snagged on a tooth inside her mouth! I was skeptical about removing the netting from the mouth - I was thinking "surely it'll just fall out on its own eventually...." But Chris was persistent and willing to work at getting it loose. When the snake wouldn't open its mouth, he gently pried it open with a small plastic garden row marker! I've never seen anything like it - snake dentistry! 

The last piece of netting came loose and we sent her slithering on her way!  

By the time we released snake #3, it was completely dark outside.
You can just barely see the last snake slithering away in this picture.

Snakeskin found in compost bin, probably
from the largest snake.

I saw the largest snake a few more times in the weeks after that, and it was a little like visiting an old friend! The shed felt surprisingly empty now that my neighbors were gone. Twice we found snakeskins in the compost pile - one large, and one smaller. 

The pile of blueberry netting was of course so cut to bits that we threw it all out. But I also looked around the shed to see if there was anything else that could similarly act as an unintentional trap. There were a few rolls of plastic fencing with fairly small openings, so I brought these inside and put them in closets in the house where they can’t potentially harm snakes. I’ll store them in the shed only during cold months when snakes won’t be around.

I have since learned that some people intentionally use piles of netting like this to trap snakes, when they don’t want them around to harm things like chickens. Not only is this a cruel way to trap snakes, it is also potentially dangerous if the snakes you catch are venomous. Once trapped, the snakes will obviously not die right away, and a hurt, trapped, and fearful snake is a snake that may strike. Pets, children, and others who are not aware of the danger of the snake could be bitten, with serious consequences.  

Snakes are good and helpful creatures, and gardeners in particular should be happy to have them around. Like spiders, even if they seem “creepy” to us, their natural behaviors do quite a bit to help us out by controlling the populations of other critters that can cause us problems. Even if snakes aren’t your thing and you’d rather keep your distance and never see them, they are a natural and important part of the ecosystems where they live. To keep snakes safe, if you use netting to keep birds away from blueberries or other plants, try to tie it off above the ground where snakes are less likely to get into it. Store netting and other similar items in places where snakes cannot get into them. 

The Lion and the Mouse

A friend of mine told me this story reminded her of Aesop's fable about the mouse and the lion. The lion, who could easily kill the mouse, lets the mouse go when the mouse claims he will repay the lion by helping him someday. The lion is skeptical that this could ever happen, but it does – in some versions of the story the mouse releases the lion from a trap by chewing through the ropes, and in other versions removes a thorn from its paw. 

My friend thought we were the lion, and now that we've released the snakes when we could have easily killed them instead, they had to come back and help us out somehow! And in a way that is true and they do, because they are one of our important garden partners. While I don't have any proof that they have been killing pests, it is a good guess that a six-foot long blacksnake near the garden seriously cuts down on the number of small rodents! Thank you snakes. And while I'm sorry they got caught in our netting, I am glad they were all successfully released, and glad we had the chance to have such a close encounter with some of the wonderful nature of Lutherlyn.   

Toothpaste Slime Mold

   a.k.a.

Wolf’s Milk Slime

   a.k.a.

Lycogala epidendrum

by Holly Schubert

Photo by Lisa K. Suits   from http://mdc.mo.gov/discover-nature/field-guide/wolfs-milk-slime-toothpaste-slime

From time to time we come across these little pink bubbles while walking in the forest with campers or students. They are small, but eye-catching, and people often want to know, “what is that?!” These are commonly known as Toothpaste Slime Mold, sometimes Wolf’s Milk Slime, and their scientific name is Lycogala epidendrum.

Toothpaste slime mold at Lutherlyn, 2014.

They look like funky mushrooms, but slime molds are not really a fungus. In fact, scientists have had a hard time pinning down exactly what they are. The Conservation Commission of Missouri says slime molds “at one time were regarded as animals, then thought to be plants, then fungi. Now, because of DNA studies, slime molds are believed to be closer to the protozoa.”

These organisms are also pretty amazing!

Slime molds like the toothpaste slime mold are known as plasmodial slime molds, and have two main life stages. In the first plasmodium stage, the slime mold is like a huge single-celled amoeba (huge for an amoeba anyhow!), and can creep along on dead plant matter in search of food, consuming bacteria, yeasts, and fungi. (It is this feature of slime molds that was part of the inspiration for the 1950’s horror movie “The Blob”!)

When there is no more food source available, the plasmodium gets ready to reproduce and turns into a fruiting body – essentially a spore sac. This is the second life stage, and this is what we see – in a toothpaste slime mold it appears as little pink bubbles growing on the sides of trees and dead logs. 

toothpaste slime mold at Lutherylyn, 2020.

When immature, its insides are a pink goo that looks a little like toothpaste, hence one of its common names. As the fruiting body matures, the insides dry out and turn brown or gray. The dry spores then disperse on the wind to create more slime molds. The change from pink and spongy with oozy goo inside to dry and gray-brown with a puff of spores inside can take place in a single day. If you see a slime mold and go back to look at it tomorrow, it may be completely gone!

"Pink and brown slime molds" by Benny Mazur from Toledo, OH                Licensed under CC BY 2.0 via Commons -https://commons.wikimedia.org/wiki/File:Pink_and_brown_slime_molds.jpg#/media/File:Pink_and_brown_slime_molds.jpg

So if you see those cute bubble-gum pink bubbles on a dead log, take a close look! And keep in mind that they started out as a “huge” single-celled organism that can move under its own power, consuming food as it oozes along; that its true nature has puzzled scientists for decades; and that it may be gone within a day. Scientists have even seen some slime molds learn from their environment and change their behavior in anticipation of expected conditions! Nature truly is full of weird wonderful beauty!

For further reading:
Wikipedia, Slime Mold
Wikipedia, Lycogala epidendrum
Missouri Department of Conservation, Wolf’s Milk Slime (Toothpaste Slime) 
Discover, Slime Molds Show Surprising Degree of Intelligence 

Little Tiny Predators

     Shrews are, arguably, the smallest mammals in Pennsylvania.  Weighing in at less than an ounce, these insect eaters are often confused with their cousins the moles.  Moles hunt for insects and earthworms underground, burrowing through the soil and rarely coming out above ground.  Shrews, on the other hand, hunt above ground, although they do tunnel through snow and fallen leaves.
     Moles are known for the tunnels and mole hills that they leave behind.  The presence of shrews is only visible in the winter when there is snow cover.  The amount of shrew evidence can be astounding, as we have found this winter at Lutherlyn.

     In the picture above, you can see a shrew trail entering a tunnel in the snow.  The trail and tunnel are about 5/8" wide.  In the photo below, you can see a shrew trail crossing a gray fox trail.  The fox print is about 1 1/2" wide.

                                          

     These tiny predators are amazing for their size.  They live fast and die young.  A shrew's heart may beat 1,200 times in a minute!  With a metabolism like that, it is no wonder that they have to eat almost constantly.  Young shrews reach adulthood in four to six weeks after birth.  However, shrews rarely live for longer than one year.  They are easily killed by floods, sudden temperature changes, starvation, and even fright.  Predators also kill some, but most are not eaten since shrews give off a musky odor that most predators do not find palatable.

     One of the shrew species that lives in Pennsylvania, the northern short-tailed, has toxic saliva.  When it bites prey, the shrew's saliva can slow down or even kill the insects, worms or other creatures that it wants to eat.
     It has got to be hard to find enough food in the winter to keep that little body going.  I suppose that explains all of the tracks that we find throughout the forest.  These animals have to spend most of their day trying to find enough food to keep their little heart beating.  One of the benefits of this long winter is that it has made me take notice of how animals survive bitter cold and snow.  It has really made me appreciate many of these creatures that we seldom see, but are supremely adapted to survive (and thrive) in a long cold winter.

Snow Rollers

   It is always fun to see something that you have never seen before.  Such was the case this past Monday morning in some parts of western Pennsylvania.  Many of us awoke to what appeared to be snow balls or snow "boulders" strewn across lawns, farm fields, even the basketball court and softball field at Lutherlyn.  For most of us, this was our first glimpse of snow rollers.

   Snow rollers were formed by a "perfect storm" of conditions.  We had about five inches of powdery snow fall on Saturday.  On Sunday night the temperature warmed up into the 30s, which made the snow more cohesive.  A strong wind (20-25 mph) then began to blow and it was able to roll the snow particles across open areas.  The particles accumulated in much the same way that a snow ball is rolled to make a snowman.

   If you look closely at the above picture, you can even see the track left by the snow roller as it was blown across the landscape.  Most of the snow rollers at Lutherlyn were no bigger than a soccer ball, but I saw one in a neighbor's yard that was 20" long and 9" in diameter.  The majority of the snow rollers were solid, but there were a few with a hole in the middle.  These have been coined "snownuts" for their resemblance to doughnuts.

To me, it is a good lesson.  There is always something new, something that you have never seen before, if you only take the time to look and explore.  Sometimes you have to look really hard to see something new, but other times it is right there in your front yard, as big as a basketball.

Winter Tracking

     Sure its cold out there, its winter after all, but the snow can give us so much insight into the animal world around us.  Unlike the rest of the year, the snow records the travels of the mammals who are sharing our forests and neighborhoods with us.  Deciphering the tracks is not very difficult, if you know what to look for.
     I found this print the other day.  You can very clearly see the pads of the foot and at least three toenails/claws.  Thankfully, it wasn't the only print, there was a series of prints, which are known as tracks.
    When looking at tracks, you can quickly narrow down what the animal is by looking at the type of track pattern that the animal is exhibiting.  This one is a perfect walker, which means that this animal places its hind feet in the exact spot as its front feet. So, there are only two prints, not four, left behind. There are other animals that aren't so "perfect" and you will find their hind foot print close, but not on top of their front foot print.  They are called imperfect walkers.  Other mammals, like squirrels, mice, and rabbits have large back legs and leap or hop when they move from place to place, so they are known as leapers.  Finally, members of the weasel family have four feet that are about the same size and bound when they move, so they are called bounders.

     Perfect walkers include animals like cats, dogs, and deer.  With pads and toenails present in these prints, it is certainly not a deer.  However, it could be a feline or a canine.  Our next step involves a handy measuring tape.  The two primary measurements that we need to take are the width of the trail that the animal has made (called the straddle) and the distance from the middle of one print to the next (called the stride).  This animal's straddle is about 10 centimeters and its stride is about 30 centimeters.  Those measurements are too large for a house cat and too small for a bobcat or coyote.  What's left?  How about a fox!  Now the question is:  Is it a gray fox or a red fox?
     In order to answer that question, we will need to measure the size of the print itself.  Using the handy measuring tape again, we can see that the print is 5 centimeters long and 4 centimeters wide.  That is a little small for a red fox, but perfect for a gray fox!
      These tracks give us about the only proof that we have gray foxes living at Lutherlyn.  They are very surreptitious and have only been seen rarely at camp.  However, we find tracks nearly every time that we go out in the winter.  We don't have to go far from main camp, either.  One gray fox has a habit of travelling by the lower lake nearly every night.
    When we teach students about animal tracking, they learn how to use a measuring tape and key to identify tracks.  We have created "tracking boards" for sixteen different animals.  These boards have realistically sized tracks with appropriate strides and straddles for each animal.  It is a great way for students to practice their measuring skills and learn how to use a key.  With a little practice, this knowledge can unlock all kinds of animal mysteries.