Wednesday, September 3, 2014

A Nature Hike at The Ridges

This past Monday I co-led a trip to The Ridges with the Ohio University Wildlife Club, of which I am the secretary. This trip was a nature hike that was aimed at finding herps, finding insects, doing some birding, and basically looking at whatever else caught our attention as we made our way through The Ridges, which is on the outskirts of Athens. We had a much, much larger group than we expected (we had about 15 members show up but were honestly only expecting 5 or so), most of which were freshmen.

The Ridges
While up on the Radar Hill Trail earlier last week, I noticed a lot of Common Milkweed individuals. I thought it would be fun to fan out and search the plants for any caterpillars (especially Monarchs) that might have been chowing down.

Common Milkweed
Common Milkweed, Asclepias syriaca, is probably the most common milkweed species here in Ohio. The photo above (Taken at Rhododendron Cove SNP in Fairfield County) shows what they look like earlier in the Summer as they are flowering. I've previously covered Common Milkweed, and other milkweed species, in a post that you can read here. At the time of the trip up to The Ridges, the flowers were long gone and the plants each contained a few "seed pods," better known as follicles. These follicles contain many silk-like hairs that are attached to seeds. These silky hairs are known as pappus, which help scatter the seeds when they are caught by the wind. 682 acres of the land at The Ridges is actually set aside as a land lab where Ohio University faculty and students teach and conduct research. As a result, I'm pretty sure all these Common Milkweed plants have been planted there and did not just occur naturally. That is actually a very good thing, as I will get into here in a moment...

Monarch Butterfly Caterpillar
The main goal I had in mind, as I stated before, was finding Monarch Butterfly, Danaus plexippus, caterpillars. We fanned out and began searching the milkweed individuals for the caterpillars. A few minutes in, a voice called out exclaiming they found one. We all closed in to get a closer look at the nicely-sized green-white-and-yellow caterpillar. Monarchs are completely dependent on milkweed species for survival. Eggs are laid on milkweed, the caterpillars hatch and eat the milkweed, they metamorphose, then the adults mate and lay more eggs onto more milkweed and the cycle begins again. In fact, there are 4 generations of Monarchs a year. The overwintering adults migrate from Mexico up to the US each Spring and lay eggs; this is the first generation. Then, those of the first generation lay the second generation, and those lay the third. The interesting ones are the fourth generation. Unlike the first three generations, which die after laying their eggs, the fourth generation actually migrates over a thousand miles to Mexico. This migration happens in October. As for our individual, I'm pretty sure he (or she) is part of the 4th generation, which means after he metamorphoses in his chrysalis, he will begin his very long journey to Mexico to overwinter!

Monarch Butterfly Caterpillar
The milkweed the caterpillars consume isn't just important as a food source, however. Milkweed species contain a type of toxin known as cardenolide glycosides. Cardenolide glycosides in the plant are consumed by the caterpillars and stored, rendering the individual toxic to predators. After metamorphosis, they still retain the toxin, but they move much of it to the wings as some predators will attack the wings first. This toxin makes the wings taste very bad, and will also make the predators, namely birds, sick. Other species simply tear off the wings of butterflies and eat the body right away. As a result, Monarchs store the most potent toxin in their abdomen, which upon ingestion will make a predator quite sick. Although the Monarch individual might be killed, this will most likely ensure that predator will never again eat a Monarch, thus overall improving the chance of Monarch survival. The bright coloration of the adults warns predators of such a fate that might come from eating them. Monarchs aren't the only species to capitalize on this toxin; many other insect species which feed on milkweed are also toxic and brightly colored to warn predators of that toxicity.

Monarch Butterfly
An adult Monarch Butterfly from Pickaway County a few years ago.
Now, many people on the trip were surprised when I told them Monarchs are badly in trouble. As in "their population has declined by 90% over the last 15 years" badly. Yes, 90%. Their population, which had a high of over 1 billion overwintering individuals in 1996, was only 33.5 million in 2013. The average is about 350 million overwintering individuals a year. This decline is so bad that many are pushing to list Monarchs as threatened, a move I am for as well. So why the dramatic decline from 2012 on? Well, there are many factors. One is the 2012 drought which killed many. Another factor was the cold temperatures of the Spring of 2013, which slowed the growth of the first generation and messed up that year's schedule. Monarchs are also facing a severe loss of habitat in their overwintering grounds in Mexico, which is hurting overwintering survival. However, they are hurting for breeding habitat too. Monarchs require milkweed, and milkweed population has declined by about 60% in the last decade. This is due to many factors such as drought, new agricultural methods, and the mowing of roadsides (a favorite place for milkweeds to grow). As an aside, please consider growing milkweed on your property. Any bit helps. Anyway, all these factors have come together to decimate the population. You might have noticed that you haven't seen many, if any, Monarchs this Summer. That's not because you're missing them, that's simply because their population is that low right now. It's horribly sad, and if this trend continues their future looks very, very grim.

We also were able to relocate a deer skeleton that I stumbled across last Spring semester. I found a semi-decayed carcass in probably March or so, and the months following that had gotten rid of everything remaining but the bones. I led the group back along a small creek and had them look for any remains of the White-Tailed Deer, Odocoileus virginianus, among the tall boneset flowers. We scanned the area once and found nothing. We gave up and turned back to the main trail. A few seconds later someone called out they saw bones. I parted the 2-foot tall plants covering the area and saw a rib and some assorted bones. A quick search of the immediate area found much of the skeleton, including the skull and both jawbones. We decided to take those back with us to show others during the next club meeting. The photo above shows the skull with the jawbones in the place they would normally be.

As Alayna, the president of Wildlife Club, pointed out, the skull was quite small. She suggested it was a fawn. I looked at one of the jaw bones and sure enough it was a fawn. How can you tell quickly? Take a look at the photo above. Deer are just like humans; new teeth form and erupt as they grow through childhood. The photo above, which has one of the molars removed, shows another molar buried in the bone. A thin piece of bone partially covers the molar. Eventually, this bone would shrink back and the molar would erupt through the gum. You had the same exact process happen as your molars formed when you were young.

So just how young is this fawn? Well, the teeth give can help us find that out. I put the above photo together quickly to help explain. So, we know it is young, but is it a yearling (1.5 years+) or a fawn? Well, a yearling has 6 fully erupted teeth. This individual only has 5, so that means it is a fawn. So, how old of a fawn? Well, the first two permanent molars, M4 and M5, have erupted completely. This places the fawn in the 6 month to 14 month range at least. We can close this gap even farther by examining how far along the third molar, M6, is. In this individual, it has not begun to erupt yet, so that closes the range down to 6-11 months. The M6 molar is, however, close to beginning to erupt, so that puts it a little bit ahead of 6 months. As a result, I would age this individual at 9-10 months, +/- 1 month.

Overall, the nature hike was really fun and really productive. I will definitely do a few more this school year hopefully. Thanks for reading! I know this was a wordy post, but there's just so many interesting things to talk about. I could have gone on much longer, but I tried to keep it somewhat sane! Thanks again!


  1. Hey Kyle, Dennis here from the Field Biology blog. Thanks for adding many of my posts to your Google page. I'm just up the road from you, so we should meet sometime.

    1. Hello Dennis!

      No problem! And that sounds fun; we should definitely do that some time!

  2. Nice article. Well done. However, I wonder if you would have had 15 to show if communicators had to stay turned off and put away. Six out of ten in the photo have out. They may as well stayed in the dorm.