Why did the tarantula cross the road? Well, no, not just to get to the other side. Fall in the desert is the time of year when male tarantulas go on a “march” to seek out females. It’s not that they particularly look for roads to cross, but because there are so many of them in such a large expanse of territory, there are bound to be some of them that come across roads. (Some of them can cover 50 miles in their lusty trek.) So it follows that driving along roads is where you’re most likely to see them. And the fall march can be a sight to behold, depending on the population. The populations seem to follow a boom and bust cycle, depending on the weather and the food availability. The number of males may be greatly diminished if the rains have been sparse.
Here in southern Nevada, the march goes from September to October. Visitors to the Valley of Fire State Park reported seeing some of the spiders on the move in September. As of this writing, in October, folks in southern Nevada are seeing a lot of them. They may have been somewhat delayed this year due to the lingering hot temperatures. Gabbs, Nevada is home of the world’s largest tarantula migration. The “migration” can start as early as August in Texas, and in other areas such as the Four Corners region, it begins in October. I witnessed my first tarantula migration in Zion National Park around Labor Day. By the time the cold weather approaches in November, the march is over. If there are any males left wandering about at this time, they are doomed to perish from the near freezing temperatures.
The females have it much easier. They just stay in and about their burrows and wait for suitors to appear. Do they have to accept the first one that they see? Definitely not – a female will kill and eat males that do not suit her. Well, actually, she may kill and eat the successful one as well. All in all, it’s not a good outcome for the males. They only live a few years, then have to trek up to 50 miles just for a chance at procreating, and are doomed to die afterwards, whether from cannibalism or sheer exhaustion. The female tarantulas, on the other hand, live this selective lifestyle, in a home of their choice, selecting mates of their choice, for up to 20 years. Needless to say, females grow bigger than the males.
Now a little on the natural history of the tarantula:
There are over 50 species of tarantulas native to the southwestern and central portions of the United States. The common desert tarantula is Aphonopelma chalcodes. Its preferred habitat is dry, well-drained soils in open areas throughout the desert and grassland areas, including Joshua tree forest and creosote bush scrub.
Tarantulas are a member of the Arachnid, or spider family. That means they are animals with an exoskeleton – their skeleton is on the outside of their body. Spiders and tarantulas are not insects, but more closely related to Crustaceans, like crayfish. Tarantulas are about two inches long with black or brown hairs all over them. The body has two parts, with the head and thorax fused into a cephalothorax, and the abdomen. They have eight legs and eight eyes. Legs can be four inches long. There are also two pedipalps that look like short legs, used for touching and moving prey. Prey can be sensed by vibrations picked up by the sensitive hairs. Rather than waiting for it to fall into a web, tarantulas do chase down their prey. They then subdue it using two large fangs, which inject a venom that liquefies the inside of the prey’s body. Like other spiders, the tarantula utilizes a sucking technique for ingesting its meal.
Each tarantula lives in a burrow, or hole, which it digs itself. The webbing in the burrows actually serves to reinforce the structure and keeps it from collapsing. Tarantulas are nocturnal and come out at night to search for insects, lizards and other small animals to eat. During the day, they keep to their burrows or other sheltered sites to avoid the heat (in the summer). In winter, they will enter torpor, similar to hibernation, but it allows them to come out and hunt when it’s warm.
They do have predators, too – there is an insect that preys on the tarantula – a wasp called the tarantula hawk. The female of this large Pepsis wasp seeks out tarantulas in their burrows, then lays its eggs on the spider’s body. When the eggs hatch, the wasp larvae have a ready-made meal. Other predators on the tarantula include lizards, snakes, birds, foxes, and coyotes.
Tarantulas got their name from Taranto, Italy. People used to do a dance called the Tarantella to cure them from tarantula bites. But the bite from a tarantula is really not very harmful, just painful. And you would have to provoke the tarantula to experience its bite. When it feels threatened, the spider can also flick its urticating (barbed) hairs onto your skin, which can be irritating. This is done by rubbing its abdomen with its legs. You may see a bare spot on a tarantula’s abdomen where it lost its hair. This is often seen on captive tarantulas.
In the fall you can see male tarantulas crossing roads – they are looking for a mate. Immature males spend most of their time in their burrows, but at about three years of age, they mature and molt for perhaps the final time, becoming darker in color. If they escape being eaten by their mate, as well as predators and the cold, the males may go on for a few more years. The longest they have been known to live is 10 to 12 years. Females can live 20 years or more, and produce 500 to 1000 young at each mating.
So if you get to witness this phenomenon, grab a camera. It’s ok to park the car safely and get out to take a look, but it’s not a good idea to trap the animal under a jar. The glass magnifies the heat and can kill the tarantula. If you get to see one of these creatures, it’s best to let it go on its way – remember it is beneficial! You may also be tempted to take one of the tarantulas home with you, but please don’t do it. These guys won’t make good pets because they are on their way out anyway, so let them have a last hurrah. If you do want a tarantula as a pet, you can get more information from the American Tarantula Society, at https://www.atshq.org.
For more information on the tarantula and other southern Nevada wildlife, check out Dr. Jim Boone’s Bird and Hike Las Vegas, https://www.birdandhike.com.
Thank you for such an enlightening article. I have never seen a tarantula in person but to see so many at one time would be something to remember.
Fascinating and informative article written in a fun voice- thanks very much!
In the Palo Duro Canyon visitor center parking lot with some friends from out of town when we spotted a pretty hefty tarantula crossing the lot. No way was it going to avoid getting squashed. So I just put my hand down, it climbed on, and I took it across the lot continuing in its same direction and put it down. Only then did I realize how many “pilgrims” in the lot were staring open-mouthed at the crazy lady with the killer spider!
Coming back from Bartlett Lake in the evening back when the road to the lake was not paved, we would see tarantulas covering almost the whole road. We would stop and wait for a clear path to continue. Have not experienced that since the road was paved. Glad we were able to see this event.
Love your article, I have many tarantulas at my home and have seen 1 female with hatching young. I’m in high desert in NW AZ.
I saw a single line of tarantulas cross highway 62 between. Parker, AZ and 29 Palms, CA that was so long a lot of cars stopped to watch. There large ones and a lot of little ones. This was around dawn in the spring.
There was a tarantula outbreak at a water plant where I worked. There were many walking across the parking lot at night and my friend Art put his hand down in front of one. It crawled up his arm to his bicep then Art transferred it to his other arm before releasing the spider on the ground.
I never saw so many again, it was a one time event.
Several years ago I was traveling in my motor home from Silver City, NM to Lordsburg, NM. As I approached Hwy 70 in the flats [about 1/4 mile before Hwy 70], I stopped to watch literally thousands crossing the Hwy heading South. They were migrating! This was in September and before cellphones were popular, otherwise I would have taken a movie of the spectacle!
Yes, i remember hundreds of them crossing the road and in the backyard of a house we were visiting.sometime in the mid 70’s in Harker heights Texas.I have to ask older Brother if it really happened and he agrees.
in 1955 I was 11 yrs old living in Calif. traveling with my dad on a 2 lane hi way in Arizona. We saw a black area across the hi way ahead. When we stopped, it was about 12ft wide of thousands of Tarantulas crossing . They were not 1 ft apart they we 1 inch apart. There were so many yet to cross, my dad did not have the time to wait so he drove through them. This is something I have never see again
Often tell the tale of a road closure due to a huge Tarantula crossing on the “ol BeeLine Highway connecting Payson and Fort McDowell, Arizona ; highway patrol were stationed on both sides to flag traffic until the herd(?) crossed and were out of dangerr. BTW, what do you call a group of Tarantulas- a Congress ? 🙂
They are crossing the roads in garces hwy between Delano & lost hills going south
I got to witness this once in Texas. I was driving into town at night. At first I thought it was just balls of dirt. Then noticed they were moving. I got out and seen what was hundreds of them crossing the road.
I walked down the road to see how far it went and was amazed at the shear numbers of them. I later told the storie to some older people and they thought that plowing the field caused them to move. Now I know why.
I never seen it again after 40 years.
Hi Mark,
That’s an interesting story. Sure, tarantulas make their underground burrows in open ground, on cliff faces, between rocks, between tree roots, and sometimes even under bark. Due to the propensity for Joshua trees to occupy tarantula territory (at least in southern Nevada), I’d say that’s very likely. I’m wondering if your friend found baby tarantulas, because adult tarantulas usually live alone. I don’t know about multiple burrows around one tree – something to look up. Meanwhile, if you’re suffering from a little arachnophobia, this page on the DesertUSA site will help:
https://www.desertusa.com/july96/get-rid-of-tarantulas.html
By the way, did the Joshua tree survive indoors?
Best to you
A friend at work told us a story about a relative of his having a joshua tree in her house.
He said that her apartment was infested with tarantulas because the guy who gave it to her dug it up outside and aparently these tarantulas make there nest in the roots of this tree? is that true?
This story gave me the willys and I was wondering if it was true they make nests in the roots of the joshua tree.
I stumbled upon your tarantula article while researching Gabbs NV. It is very informative and concisely written. Thank you.
Great write-up. Check out these guys…
https://www.flickr.com/photos/dalmdad/3087828764/in/set-72157625042098610/
https://www.flickr.com/photos/dalmdad/5133794595/
Margie — Nice article. Thanks for you efforts in environmental education! Cheers, Jim