9 Woolly Bear Caterpillar Predators, And How They Defend Themselves

What are the woolly bear caterpillar predators in the wild, and how do they protect themselves from these hunters? Read on to learn about the fascinating defense mechanisms of these tiny creatures

Tiny caterpillars are easy prey for hunters in the wild. This happens because they are easily accessible and full of protein.

But these tiny caterpillars have evolved a defense system of their own that helps them to steer clear from the dangers of the wild.

In this article, we will talk about the woolly bear caterpillars, what hunts them, and how they protect themselves from such dangers.

What Are Wooly Bear Caterpillar?

The woolly bear caterpillar is the larval form of tiger moths. there are several species of Tiger moths, such as Giant Leopard moths, Isabella tiger moths, Eastern Tiger moths, and so on. 

These worms are known for the thick coat of bristle-like hair on them. In fact, there is a myth surrounding their hair that says that one can predict the upcoming winter by looking at them!

They have a black-colored body with a rustic brown band in the middle. However, the color of the body keeps changing with age and the feeding capacity of these insects in the caterpillar form.

The woolly bears can be found across different parts of North America, Mexico, and Southern Canada. Being herbivorous in nature, they actively eat leaves from small plants and leaves of elm, maple, and more.

Who Eats Them?

One of the main predators of woolly bears is birds that hunt hairy caterpillars.

Brown thrashers, American crows, and rufous towhees are some of the ideal examples of birds that prey on woolly bear caterpillars.

Apart from birds, they are also hunted down by mammals like raccoons, red foxes, deer mice, coyotes, and other larger mammals.

Insects like parasitic wasps (such as yellow jacket wasps) and flies are also dangerous for them.

Since they have a lot of predators, woolly bears have their own defense mechanism to protect themselves.

Wooly Bear Caterpillar Defense Mechanisms

Woolly bears usually curl up like a ball and play dead whenever they feel threatened. They lie motionless (or rather play dead) in this position until the threat has passed.

There are other techniques and traits that these insects use to keep themselves protected against the cold and predators. Let us look at them in detail in the sections below.

Surviving Extreme Cold

Usually, it is tough for caterpillars to survive the extremely cold winters, but the woolly bears can survive in temperatures that go way lower than the 0 degrees F.

During such times, they produce a substance in their body called glycerol. Glycerol prevents the inner body parts from getting frozen.

Thus the caterpillar slowly freezes during the winter, but they still remain alive as its internal organs are intact and working correctly.

They can survive temperatures that are as low as -90 degrees F. At times, they survive the winter inside an ice cube. Fascinating, isn’t it?

They also search for warmer places, like crevices in the rocks, abandoned logs, etc., to hibernate throughout the cold season. Thus they can easily survive tough to mild winters.

Bristles To Defend Against Large Predators

The stiff hairs or bristles on the body of these caterpillars are extremely important to save them from larger predators like raccoons and red foxes.

As mentioned above, these worms curl up like a ball when they sense danger. When they curl up, the bristles get pointed outside and provide protection to the internal organs of the body.

Since these bristles are dangerous for insects like wasps, they usually refrain from attacking.

When it comes to larger predators, if they try to swallow the caterpillar, the bristles will get stuck in the throat, causing gagging, coughing, and irritation.

This is also one of the main reasons why you should keep pets like dogs and cats away from the woolly bear caterpillars.

Self-Medication Against Parasitic Larvae

Apart from the large predators, there are some parasites that attack these worms from the inside.

To deal with such predators, they have developed a unique “self-medication” technique.

When parasitic flies lay eggs on these caterpillars, they start consuming plants with bitter compounds, which keeps the parasitic larvae away from them.

Interestingly, the caterpillars don’t normally consume these plants as they contain pyrrolizidine alkaloids which can affect their growth. They only do it when faced with parasites.

What Do They Eat?

Wooly bears are herbivores, and they mainly feed on plants, herbs, leaves, and more. They usually like to eat herbaceous plants that are low-growing and bear seeds.

Usually, they prefer eating fallen leaves rather than grass or plants. Clovers, curly dock, and dandelions are some of their favorites.

They also eat leafy vegetables like spinach, cabbage, and more. If there are no fresh leaves to consume, they will consider eating blades of grass, maize, barley, and more.

Frequently Asked Questions

Wrap Up

Being small worms, the woolly bears fall at the bottom of the food chain, but despite this, it is fascinating to see the tiny tricks they use to keep themselves safe from predators and the weather.

We hope that you found the article informative and it answered your questions as much as possible. The unique defense mechanisms of these bugs make them even more interesting than the legends and myths that surround them

Thank you for reading!

Reader Emails

Our readers have often been enamored with these cute and cuddly caterpillars, asking us questions about how to keep them safe and protect them from the elements and predators.

Read on to learn more about these discussions and some strategies that they have been following to keep woolly bear caterpillars safe.

Letter 1 – Grammia Tiger Moth

 

Tangier Island bug
This was seen on the beach on Tangier Island on the Chesapeake in mid-October of this year.
Roberta Wallace, Manlius, NY
PS Great site. I’ve learned a lot browsing through old queries. Thanks in advance for identification.



Hi Roberta,
We do not have the skill to take this Tiger Moth to the species level, but it is in the genus Grammia. Just a peek on the BugGuide site will show you how similar the various species in the genus are. If we were gambling, we might say Parthenice Tiger Moth, Grammia parthenice.

Letter 2 – Geometrid, not Unknown Tiger Moth from Oaxaca

 

(05/19/2008) Oaxaca Moth
Dear Bugman,
You were recommended to me as someone who might be able to help me identify this beauty. I took this picture in Oaxaca, Mexico on 10/30/2005. The closest thing I have found on the net are tiger moths… but nothing with these exact markings. In it’s resting pose the moth was approximately 2.5" wing tip to wing tip.
And I echo the sentiment, you have a wonderful site!
joAnn
Los Angeles, CA



Hi joAnn,
The best we can do at the moment is that this is a Tiger Moth in the family Arctiidae. We will contact an expert in the family, Julian Donahue, to see if he recognizes the species.

Update: (05/26/2008)
Dear Daniel,
It is not an Arctiid. It is a Geometrid (Subfamily Ennominae). Pantherodes unciaria Guen

Letter 3 – Wheel Bug eats Wooly Bear

 

Armored Bug–Doing Battle and Taking Prisoners in Canonsburg, PA
Hi Bugman. I think this is the dreaded "wheel bug". I’ve never seen one before, but I was able to identify it (at least tentatively) through your website. Thanks for a great resource–wish you’d do a print version I could keep in my pocket so that when I encounter these beasts, I’d be better prepared. 😉
Misty Doy



Hi Misty,
it is ironic that a few minutes ago we responded to a reader who was nervous that an Assassin Bug was going to eat the Anise Swallowtail Caterpillars she was raising, that we couldn’t recall seeing images of Assassin Bugs feeding on caterpillars. Your documentation of a Wheel Bug feeding on a Wooly Bear is wonderful. We have toyed with the idea of a book, but first we must find an interested publisher. Also, we doubt that our book would make a very good field guide. We strongly recommend Eric Eaton’s Kaufman Guide.

Letter 4 – Nevada Tiger Moth, we believe

 

Moth Pictures Location:  West Los Angeles October 8, 2010 10:17 pm One morning, leaving the house for work, I found this attractive moth on the door jam. It was late spring in Southern California. Also, I include a close up of a Dragonfly that was also in my yard. I live not far from the wetlands in Playa Vista, I’m not looking for bug ID but thought I’d share the pictures before I clean out the hard drive. Signature:  Phil H.

Hi Phil, Your beautiful moth is a Tiger Moth in the genus Grammia, and of all the possibilities presented on BugGuide, we believe it is the Nevada Tiger Moth, Grammia nevadensis.  BugGuide has this information on the species:  “Apparently multiple generations per year (probably 2 to 4 depending upon the local climate). Overwinter as larvae, and these are often seen abundantly on warm winter days. Larvae also occur in at least one or two more broods through the spring and summer. They form an oval, loose cocoon of silk, incorporating their own bristles and sometimes gravel, bits of leaves etc. Cocoons are mostly formed under debris or rocks or in cracks and crannies in wood or rocks.“

Letter 5 – Why is a Brazilian Tiger Moth in Missouri????

 

Ed. Note:  And even more importantly, why is the exact same image submitted by Shana j appearing on other websites????? Subject: Need Id Location: St Lois Missouri September 15, 2015 10:34 pm Really curious’ Signature: Shana j

Dear Shana j, Though it resembles a Tiger Moth, we are pretty sure it is not in the subfamily Arctiinae because our initial search on BugGuide did not provide an ID.  Perhaps one of our readers will be able to assist on this while we sleep on it.

Letter 6 – Figured Tiger Moth, we believe

 

Subject:  Moth Location:  Southold, Long Island, New York July 18, 2017 Hi Dan here’s  a beauty it was on my deck. Southold LI NY. Very happy to sit on my finger. Please let me no what she is. Thank you Mary

Dear Mary, This is a Tiger Moth in the subfamily Arctiinae.  We believe, based on this BugGuide image, that it is a Figured Tiger Moth.  Did you get a look at its underwings?  It seems there are various degrees of red on the underwings, with this BugGuide example being very red.  There are some similar looking Tiger Moths in the genus, so our identification is questionable at best. 

Letter 7 – Donovan’s Tiger Moth from Australia

 

Subject:  Possible Tiger Moth Geographic location of the bug:  South-East Queensland Date: 01/14/2018 Time: 11:38 PM EDT Your letter to the bugman:  Hi, my girlfriend found this moth attracted to a light in south east queensland, about 1 hour both west of the coast and South of Brisbane. It’s possible tiger moth though we do not know that species. How you want your letter signed:  Jayden Waters

Dear Jayden, You are correct that this is a Tiger Moth in the subfamily Arctiinae.  Thanks to the excellent images and archives on Butterfly House, we were able to identify your moth as Donovan’s Tiger Moth, Aloa marginata.  Donovan’s Tiger Moth is also pictured on iNaturalist and the Brisbane Insect site where it states:  “The moth is white in colour, with two black lines on each forewing. There is the black and orange line along the edge of each forewing as well. Its abdomen is orange-red in colour with black spots on each segment.”