Fact Check: "Poisonous Canadian Caterpillar Invades Midwest!"

Every year around the beginning of Autumn I see a story passed around on various social media outlets, especially Facebook. All these stories are titled something to the effect of "Poisonous/Venomous Caterpillar Found in *assorted locations*," and they're all about the little caterpillar of the Hickory Tussock Moth. Even news outlets pick this story up. Sadly, the claims these stories make are pretty much completely wrong. Here's a fact check on the Hickory Tussock Moth.

The Hickory Tussock Moth, Lophocampa caryae, is a species belonging to the Tiger Moths (Tribe Arctiini). The rather dashing adults look like this. The caterpillars, on the other hand, are black and white. These caterpillars are covered in white hairs with a central line of black hairs running down their back.

Reports of the Hickory Tussock Moth courtesy of Butterflies and Moths of North America.

The first thing I want to clarify about this species is their range. Most stories act like these caterpillars are rare in whatever state they're writing about, and that they are coming in from some other location. One of the most hilarious stories I've seen claimed this was a native Canadian species that was "invading Ohio." The Hickory Tussock Moth is actually a really common species throughout New England and the eastern Midwest. Their range also extends north to the very southern portion of the Canadian province of Ottawa. If anything, these aren't a "Canadian species," but an American one that barely extends into Canada. And these caterpillars aren't exactly rare across their range either. I've seen a dozen or so during a single hike before, and that was without trying to look for them. 

But the main thing I want to talk about is their supposed venom/poison, which many stories will say is very dangerous to humans. First, let's clarify what poisonous and venomous means. Poison means a toxin that is ingested (i.e. if you eat it and get sick, it's poisonous). Venom is a toxin that is injected into you via fangs, a stinger, or some other modified part of the body (i.e. if it bites or stings you and you get sick, it's venomous). Unless you plan on eating a caterpillar, the only way it could be dangerous to you is through venom. But is the Hickory Tussock Moth caterpillar venomous?

The short answer is no, the Hickory Tussock Moth caterpillar is not venomous; however, it is a bit more complicated than that. So, let’s start with the basics. Many caterpillar species are covered in hairs called setae. These setae help with sensation, like how a cat’s whiskers do. Many times these setae are harmless (like in the Woolly Bear), but in some species these hairs can break off into an animal’s skin and cause irritation, sort of like a cactus’s spines or bristles. In some other species, like the caterpillars of the Flannel Moths, these setae have been modified into hollow spines, and at the bottom of the spines are venom glands, sort of like a bee’s stinger. The caterpillars with these spines and venom glands can truly be called a venomous caterpillar, but does the Hickory Tussock Moth caterpillar have these? The answer is no. Hickory Tussock Moth caterpillars do not have stinging spines nor venom glands (Hartmann 2009, Kuspis et al. 2001). They do, however, have the irritating setae that I previously mentioned. But, are they really that irritating?

Citations:

Hartmann, T., 2009. Tiger moths and woolly bears. Behavior, ecology and evolution of the Arctiidae.

Kuspis, D.A., Rawlins, J.E. and Krenzelok, E.P., 2001. Human exposures to stinging caterpillar: Lophocampa caryae exposures. The American journal of emergency medicine, 19(5), pp.396-398. Link.

People will often comment on these stories with horror stories about how either they or someone they know touched one of the caterpillars and had a horrible reaction, with some even saying they had to go to the ER. This is not the norm, at all. Some people are, for whatever biological reason, hypo-sensitive to the setae of this species. They can experience pain and bad rashes, yet the average person will not experience this. Let me give you an analogy. Some people are allergic to peanut butter, but the vast majority of people aren’t. Would you say peanut butter is poisonous/dangerous to the average human? No, you wouldn’t. It is the same with the Hickory Tussock Moth caterpillar. A very small percentage of people will have a bad reaction to the setae of this species, but the average person will either have no reaction, or they might itch a bit. To prove a point for science, I pet this Hickory Tussock Moth caterpillar. And not just once — I pet him several times. And what happened? Pretty much nothing. I had a few itchy sensations, but nothing hurt and there was no rash or anything. So much for being a scary and dangerous caterpillar!

Is the Hickory Tussock Moth a species to fear? Not at all! These little guys are just another victim of social media getting animal facts incorrect. It's especially sad to see news organizations (like CBS which claimed this caterpillar wasn't native to the US and that is has venom glands) perpetuating these incorrect "facts." Thanks for reading!

Hiking The Narrows

A couple weeks ago I covered one of Zion National Park's most well-known hiking experiences, Angels Landing. This week I want to cover probably the most well-known hiking experience at Zion Nation Park, The Narrows.

Zion National Park lies in the Southwest corner of Utah. Although the park is huge and has many different areas, the main and most-visited area is the famous Zion Canyon. This canyon can be broken up into two main parts: the upper canyon (The Narrows) and the Lower Canyon. The photo above shows the beginning of the Lower Canyon portion as looking up-canyon from atop Angels Landing. Where the canyon pinches off in the middle of the photo is where The Narrows, a slot canyon, begins.

Why is there a rather-abrupt change from the slot canyon that is The Narrows to the quarter-to-half mile wide Lower Canyon? It all has to do with the rock layers. During the Mesozoic Era, the area that now encompasses Zion NP used to be a flat coastal plain. Most of the rocks in Zion were laid down during the Jurassic Period. Beginning in the Cretaceous Period, this entire region of the West experienced a period of uplifting, where the layers of rocks were slowly thrust upward to heights from near sea level to over 10,000 feet above sea level. The ancestral Virgin River, through the power of erosion, began to cut downward through these rock layers as the layers were uplifted. When the Virgin River arrived at what was to become Zion NP, it hit the massive layer of Navajo Sandstone (which is upwards of 2,200 feet thick). Sandstone is a rather hard rock which isn't easily eroded. Generally speaking, soft rocks form broad canyons and slopes when eroded, while harder rocks tend to form cliffs and slot canyons (A slot canyon is essentially a really narrow canyon that is deeper than wide). The Virgin River, trying to follow the path of least-resistance to the sea, cut straight down through the Navajo Sandstone Formation. This resulting deep, but narrow, canyon became known as The Narrows.

Heading toward The Narrows.

After the Virgin River cut through the entirety of the Navajo Sandstone Formation, it ran into the Kayenta Formation. The Kayenta Formation is a rather soft formation, and the Virgin River was able to erode a much wider canyon. The transition between The Narrows and the relatively wide Lower Canyon occurs at the transition between the hard Navajo Sandstone and the soft Kayenta Formation below it.

Riverside Walk Trail (Left), Southern Maidenhair Fern, Adiantum capillus-veneris (Right)

With this post, I want to take you on a pictorial journey through the day-hike section of The Narrows. I hiked 4 miles up The Narrows during a warm day in late July, and I have to say it was one of most fantastic and unique hiking experiences I've yet to have. There are two ways to hike The Narrows. The easiest way is bottom-up. For those wanting a more hardcore experience, you can do the top-down route. This is a 16 mile one-way backcountry experience which requires a permit and a lot of hiking experience. The most common way to experience The Narrows is the bottom-up route, which is the route I chose. It is non-technical, requires no permit, and can last as long as you want. The bottom-up route begins at the Riverside Walk trailhead, a mile-long paved trail beside the Virgin River. Although you're in the desert, the cool, moist microhabitats created by the tall cliffs and seeping springs result in an explosion of green. One point of the trail passes a marsh, while parts of the cliff walls near seeping springs are covered in plants like the Southern Maidenhair Fern (pictured above on the right).

Mystery Falls

After a mile, the paved trail ends, and The Narrows begin. There is no "trail" through The Narrows. The vast majority of your time will be spent wading through the Virgin River itself. It's a very different kind of hiking experience. You have to watch each step, as not only are you competing against the current, but the riverbed is made of large, slippery rocks. I watched dozens of people slip and fall into the water. Although I did it without trekking poles, I wish I had brought them. One of the first stand-out features in the canyon is Mystery Falls, which is the steep orange slope in the center-right of the photo above. There are several opportunities for technical (requiring specific rock-climbing equipment and knowledge) canyoneering within the park, and Mystery Canyon is one such opportunity. Mystery Canyon requires 12 rappels, and the final rappel is down the 120-foot Mystery Falls. On my return hike, I stopped to watch a few hikers rappelling down the slippery algae-covered waterfall. Seeing hikers rappel down a waterfall is a rather interesting activity to watch. If you want more info on this technical hike, visit this Canyoneering USA page.

The Narrows is probably the most-popular hike in Zion. When I did it, I passed hundreds and hundreds and hundreds of people. People are drawn to this hike not only because of the beauty and ease of access, but also because of the opportunity to escape the harsh heat of the park. Although it was 90 some degrees out in most of the park when I went, the canyon itself was about 70 degrees. The Virgin River was very cool too, but not uncomfortable. Because of these features, tourists flock to the trail. The first mile or two can seem like an amusement park with the amount of people present, but the number of people on the trail drops off steeply after about 2 miles. I have to admit, I didn't expect it to be as busy as it was, but you quickly leave the hordes of people after about an hour of hiking.

The soaring walls of the canyon quickly narrow as you make your way upstream. The giant boulders and carved sandstone walls remind you of the time and power that it took the Virgin River to carve out this canyon.

About 2.5 miles from the start of The Narrows, you run into a fork in the canyon. If you hang left, you continue on with The Narrows. If you hang a right, you enter Orderville Canyon, a smaller side canyon. Orderville Canyon is narrower and darker than The Narrows proper, and it was a lovely little place to explore. Those, like me, who are doing the bottom-up trek cannot go past a certain point in Orderville Canyon. The turn around point for bottom-up hikers is just a bit around the bend in the photo above. You can, however, get a permit and do the entirety of Orderville Canyon from top-down. It does, however, involve some technical canyoneering skills (rappelling). If you want to read more about the Orderville Canyon hike, check out this Canyoneering USA link!

Wall Street in The Narrows, with 1,500 foot canyon walls and the river reaching from wall-to-wall in most sections (I hiked in low water levels, so there's more exposed land than what there normally is).

It wouldn't be a post on a slot canyon without talking about the inherent dangers of hiking in one. I did this hike during the North America Monsoon season. During the late summer months, storms with torrential rain can pop up anywhere out West. Flash flooding is a serious concern, and even more so in a slot canyon. The Narrows regularly closes several times a year when there's a threat of flash flooding. Why? Because there can be literally no place to go. In some sections, there can be high ground to seek refuge on if you're caught in a flash flood. However, many sections of the canyon don't offer such protection. Take, for example, the Wall Street section of The Narrows, just upstream from Orderville Canyon. As you can see in the photo above, the Virgin River stretches wall-to-wall. There is no safe high ground. If a flash flood comes roaring in while you're here, you will die. You cannot outswim a flash flood, mainly due to the force of the current and the debris the river picks up. Imagine having trunks of trees ripped-out from the flood hurtling toward you at 30 mph; it's not going to be a pretty ending. Check out this Youtube video of a flash flood at The Narrows to see the danger of such a flood.

The National Park Service will close The Narrows to hikers if it seems a flash flood is potentially possible for that day. That doesn't mean that one can't pop up unexpectedly with no warning. Even if the sky is blue over The Narrows, a rain event out of sight at the headwaters can send a wall of water downstream. Be aware: if you hear a rumbling in the canyon, get to high ground. If the water begins to change color, get to high ground. If the water seems to be ever-so-slightly rising, get to high ground. Just be aware, and if it seems like it might be a bad day to do this hike, don't do it. Remember, in a national park your safety is your responsibility, not the National Park Service's.

If you're ever in Zion National Park, and you can (safely) hike The Narrows, I highly, highly suggest that you take the opportunity to do so. It is not an experience you are going to ever forget. The towering walls, the interplay between the sunlight and shadows, and the refreshing water of the Virgin River all combine to create a fantastic hiking experience.

Thanks for reading!