Tarantulas: Defense

Summary: Tarantulas have many predators and they have developed a plethora of ways to defend themselves. Join Kiersten as she discusses these interesting and surprising behaviors.

 

For my hearing impaired listeners, a complete transcript of this podcast follows the show notes on Podbean.

 

Show Notes: 

The Tarantula Scientist by Sy Montgomery

“The Natural History of Tarantula Spiders” by Richard C. Gallon https://www.thebts.co.uk/old_articles/natural.htm

“Parasites of Tarantulas,” Pizzi, Romain. Journal of Exotic Pet Medicine, Vol 18, Issue 4, pg 283-288. https://www.sciencedirect.com/science/article/abs/pii/S1557506309001153

 

Transcript

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Kiersten - This is Ten Things I Like About…a ten minute, ten episode podcast about unknown or misunderstood wildlife.

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Kiersten - Welcome to Ten Things I Like About… I’m Kiersten, your host, and this is a podcast about misunderstood or unknown creatures in nature. Some we’ll find right out side our doors and some are continents away but all are fascinating. 

This podcast will focus ten, ten minute episodes on different animals and their amazing characteristics. Please join me on this extraordinary journey, you won’t regret it.

This episode continues tarantulas and the eighth thing I like about these awe-inspiring arachnids is how they defend themselves.

I know lots of people are afraid of tarantulas, but tarantulas have predators that they’re afraid of too. So they’ve developed a plethora of ways to defend themselves.

The first way a tarantula will defend themselves from predators larger than themselves is to stay out of sight. They accomplish this quite well by only coming out at night. Tarantulas are nocturnal, except during mating season, as we learned in the previous episode, when males are out looking for females. When they come out at night during the rest of the year, they do try to stay under cover. This is also where the prey they are hunting is most often found. 

What kind of predators are these tarantulas hiding from? They actually have quite a few natural predators including foxes, skunks, coyotes, large lizards, birds, and even some fellow invertebrates such as centipedes, scorpions, and tarantula hawk wasps. In Cambodia, they have to worry about being eaten by people. They are considered a delicacy. Certainly not on my menu, but…

If hiding does not keep the tarantula safe, the next step they’ll take to ensure survival is to run away. I’m not seeing too much fault in this strategy, honestly. The one who runs away, lives to fight another day. I would love for those of you who are afraid of tarantulas, or those of you that have friends or family that are afraid of tarantulas, and think they are hideous spiders out get you to remember that the first two behaviors they use when confronted with danger is to hide or run away. They are not vicious invertebrates out to bite humans. If they come across us, they really don't want to have anything to do with us and will run away.

Having said that, sometimes you don’t have the ability to run away. When a tarantula finds itself in a position that does not allow for running away, a third behavior called threat posturing is employed. Threat posturing is when a tarantula rears up placing their weight on the back legs and raising its front two pairs of legs and pedipalps straight up in the air.  This makes it look much bigger than it is, which hopefully will make a potential predator think twice about making a meal out of the tarantula. This posture also displays the tarantulas large fangs, which would certainly make me think twice about trying to eat it. The underside of many species is dark which highlights the red fangs making them even more impressive. To enhance this defense mechanism some Old World tarantulas, those that are found in Africa, Asia, and Europe, have brightly colored bands of yellow, white, and black under their two front pairs of legs. We believe flashing these colors is used as a threat to scare off predators.

Defense strategy number four is also only used by Old World tarantulas and involves making threatening sounds. Many species of Old World tarantula have specialized hairs, or setae, that they can use to make sounds. These are called stridulatory setae. They are typically found on the chelicerae and by rubbing the hairs together they can produce hissing or rasping sounds that can scare off a predator.  

Defense strategy number five is used by New World tarantulas, those found in North, Central, and South America. This strategy involves urticating hairs. The main purpose of these hairs is to irritate a predator to ward them off and keep them from coming back for a second try. The irritating hairs, or setae,  are generally found on the tarantulas abdomen. These hairs can be deployed in one of two ways. 

The first way is for the tarantula to rub their abdomen against a predator’s skin. The urticating hairs will dislodge from the tarantula and pierce the predator’s skin and wiggle its way into the predator’s flesh with backward facing barbs. This method is mainly used by the Avicularia species, aka pink-toes, that are native to Panama, the Caribbean, and tropical South America. The problem with this delivery method is probably obvious. You have to get really close to your predator to use this defense mechanism. 

The second way to deploy these urticating hairs gives the tarantulas a bit more room to maneuver. The Theraphosinae species of New World tarantulas can flick these hairs at predators. When threatened with no way out these tarantulas will use their back legs to brush the hairs off their abdomen and flick them into the air. The setae then penetrates the predators skin and wiggles into the flesh with backward facing barbs just like the hairs of the pink-toes. The advantage of being able to flick the hairs, besides distance, is that these hairs can penetrate the eyes of a predator. And as we all know, it’s all fun and games until someone gets poked in the eye.

Research into these urticating hairs has revealed that there are six different types of urticating hairs. It is believed that the different hairs target different types of predators. Types 3 and 4 appear to target mammals as they are more irritating to mammalian predators. Type 3 also seems to target invertebrates. More research is needed to determine if the other types target a specific predator. 

 

Let’s take a moment to reflect back on the defense mechanisms that tarantulas use to protect themselves from larger predators. We’ve discussed five so far, and there is more to come, but so far not one of these defense strategies has involved biting. I mention this because this is the main reason that tarantulas are misunderstood. People think they want to bite us! But they don’t. They really don’t want to bite a predator. It’s literally the last defense mechanism they will use and only if the first five have failed! 

Now these are all defense strategies that tarantulas use against predators that are larger than themselves, but they also have to worry about predators smaller than themselves. Let’s take a look at who those predators are and how  they protect themselves against them. 

In the southwest United States the Tarantula Hawk Wasp is a common sight in spring and summer. It’s a large wasp, growing up to 2 inches in length, with a green-black body and flame colored wings. It’s quite pretty, actually. This is also a misunderstood animal as well, as many people are afraid they might sting us humans, but that only happens if you catch them or accidentally sit on them. 

The adults are pollinators and females are the ones tarantulas must fear. The female wants to find a tarantula to lay her egg on. The wasp lures the tarantula out of its burrow and stings it. The sting immobilizes the tarantula and then the wasp drags the spider back into its burrow and deposits one egg on the tarantula. She the fills in the entrance of the burrow and leaves her egg to hatch. When the wasp egg hatches the pupa eats the tarantula and then emerges from the burrow a full grown wasp. Not the way I want to go!

There is also a species of fly that eats tarantulas from the inside. The fly lays their eggs on the tarantula. When they hatch, the maggots make their way into the book lungs through the openings on the abdomen. They set up house and eat the tarantula’s insides. It can take months for the maggots to finish off the tarantula, who goes about their daily business as usual. It becomes fatal when the maggot pupates and bursts from the tarantula’s abdomen killing its host.

Ants are a predator that female tarantulas must worry about during breeding season when they are protecting eggs sacs. Ants can invade a burrow and tear into an egg sac destroying her young.

So how so you protect yourself from these small predators? It’s difficult but tarantulas have a few tricks up their sleeves. Once again being nocturnal helps because these predators are typically diurnal. Living in burrows helps defend against the tarantula hawk wasps. Staying in an enclosed space can keep you safe because the hawk wasp won’t venture down into the burrow, but the wasps have ways of tricking the tarantula out into the open, so the tarantula must be wary of potential prey items. 

An unexpected way to defend against these predators is to have a roommate that can help you out. Two species of American tarantulas have been seen sharing their burrows with small frogs. The tarantulas do not attack them and it is thought that the frogs eat invertebrates that come into the burrow. They  eat ants that come in looking for an egg sac and, maybe, the flies that are looking for a place to lay some eggs. The frogs also get something out of this arrangement as well. They have a big, hairy bodyguard that protects them from predators that might want to eat the frogs. It’s a win, win. 

That wraps up defense mechanisms for tarantulas and I hope you enjoyed it because it’s my eighth favorite thing about tarantulas. 

 

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Join me next week for another thing I like about tarantulas!

 

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This has been an episode of Ten Things I like About with Kiersten and Company. Original music written and performed by Katherine Camp, piano extraordinaire.