Climate Change Could Alter Spidey Love

Every September, the small town of La Junta, Colorado puts on a whole festival https://visitlajunta.net/la-junta-tarantula-fest/ to celebrate a beloved local animal: the tarantula! Around this time of year, thousands of mature male tarantulas start to migrate en masse – but until recently, scientists didn’t know what triggered them to move out of their cozy burrows. On today’s show, biologist Dallas Haselhuhn https://www.linkedin.com/in/dallas-haselhuhn/ explains how they solved the mystery, and how climate change could affect future treks. Want to hear about more critter mysteries? Email us and let us know at [email protected] mailto:[email protected]. Listen to every episode of Short Wave sponsor-free and support our work at NPR by signing up for Short Wave+ at plus.npr.org/shortwave https://plus.npr.org/shortwave. Listen to Short Wave on Spotify https://n.pr/3HOQKeKand Apple https://n.pr/3WA9vqh Podcasts. This episode was produced by Berly McCoy and edited by Rebecca Ramirez. Tyler Jones checked the facts. Robert Rodriguez was the audio engineer. See pcm.adswizz.com https://pcm.adswizz.com for information about our collection and use of personal data for sponsorship and to manage your podcast sponsorship preferences. NPR Privacy Policy https://www.npr.org/about-npr/179878450/privacy-policy

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• 0:00Speaker 00

  This message comes from Mint Mobile. Ditch overpriced wireless and get premium wireless for less. Go to mintmobile.com/switch to see which plan works for you.

• 0:12Emily Kwong?

  You're listening to Short Wave from NPR. Hey, Short Wavers. Emily Kwong here. And today, we're going on a road trip

• 0:22Emily Kwong?

  to the Comanche National Grasslands of southeastern Colorado, near La Junta, where if you drive down a dusty road in early fall...

• 0:30Speaker 02

  Usually right around sunrise or sunset, you'll start seeing these little shadows that look like rocks crossing the road.

• 0:38Emily Kwong?

  More and more will appear. And ecologist Dallas Hasselhoff says pretty soon you realize these moving shadows are not rocks. They are tarantulas.

• 0:48Speaker 02

  Slowly meandering their way across the asphalt as you're driving at highway speeds, trying your best, hopefully, to avoid them.

• 0:56Emily Kwong?

  Tarantulas are a group of large, hairy spiders that I think are quite cute up close. But feel free to debate me on that. These tarantulas in Colorado are on a mission.

• 1:08Emily Kwong?

  Once a year, from mid-September to mid-October, Colorado brown tarantulas leave their burrows en masse to find a mate. These wanderers are sexually mature males crossing the road as the cars try to dodge them. When Dallas was a tarantula researcher at Eastern Michigan University's Schillington Arachnid Laboratory, they remember the first time they saw these arachnids in the wild.

• 1:32Speaker 02

  And I was like a kid in the candy shop. The second I saw one, I pulled over immediately. And I jumped out and I just ran straight to it.

• 1:42Emily Kwong?

  Time stopped like a slow-motion love scene with the tarantulas running to find a mate and Dallas running to find them.

• 1:52Speaker 02

  It felt like I was running through the wildflowers in the grasslands, finally seeing something, because I had only worked with tarantulas in a lab setting. This was my first time seeing wild ones, and it was beautiful. It was everything you could imagine.

• 2:05Emily Kwong?

  The tarantula migration is so beloved in the local community that every year, Tarantula Fest takes over downtown La Junta. Dallas has been a parade judge and loves it.

• 2:16Speaker 02

  It was hard not to continually get choked up, given the reputations of tarantulas and seeing a whole community come around to celebrate them.

• 2:27Emily Kwong?

  But despite the public embrace of tarantulas, very little is known about what triggers this massive migration-like event.

• 2:35Speaker 02

  We lacked such basic knowledge of their life history. No one had gotten out and done the gritty, dirty fieldwork to actually see, is there something that's triggering these males to go and mate-seek?

• 2:48Emily Kwong?

  So Dallas did what scientists do and got dirty. Today on the show, a tarantula migration mystery. What causes thousands of male tarantulas to leave their cozy burrows after years of being homebodies? And how is public opinion about tarantulas changing? I'm Emily Kwong, and you're listening to Shorewave, the science podcast from NPR.

• 3:18Speaker 00

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• 3:23Emily Kwong?

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• 4:24Emily Kwong?

  OK, Dallas, so we're talking today about tarantulas, and they have a pretty interesting life cycle. Can you just explain how male tarantulas are hanging out in the years prior to this, this big day that they go on this quest?

• 4:40Speaker 02

  Yeah, absolutely. So males will hatch out of their mom's egg sac.

• 4:46Speaker 02

  And then all baby tarantulas, when they're ready to leave their mom's burrow, they'll leave in a single file line. And then one will break off from that line and a handful will follow. And then one will break off from that line and they do this weird fractal pattern. We still have no idea what they're doing that for. It might be a dispersal mechanism. And then the tarantulas do the most boring thing in the world, right as they're babies. They dig a hole and then they sit there from anywhere between three to 10 years before they sexually mature.

• 5:22Speaker 02

  The other fun fact that I love to share is tarantulas are very cleanly. When they eat, they'll have to liquefy their prey. You know, they make a protein shake out of their food and they slurp them up. And then all tarantulas have these little mustaches, kind of like baleen in a whale. And what they'll do is, once they're done eating, they will sit there and meticulously clean that, make sure there's no food crumbs left in their mustache. And then whatever leftovers they have, they'll wrap up in their silk.

• 5:54Emily Kwong?

  They're really model citizens.

• 5:56Speaker 02

  They are, they are.

• 5:59Emily Kwong?

  All right, so you encountered these tarantulas at the moment that the male tarantulas emerged from their burrows to make this mass journey. What did you find in your research?

• 6:12Speaker 02

  Yeah, so I went out there a couple of weeks before I had kind of a hunch the males would start coming out. And I went out to the grassland every day, four times a day. I went out there right before sunrise, sometime in the morning, at the exact heat of the day. And then I went back out right around dusk and I just counted tarantulas. But I didn't see any males until early September. There was this cold snap where the temperature dropped significantly. And then all of a sudden, I saw 20 to 30 tarantulas after seeing none for weeks. And then fewer and fewer and fewer over the next couple of days.

• 6:57Speaker 02

  And then there was another cold snap in late September. And all of a sudden, I saw around 50 to 60 tarantulas in a day. And it also happened to be a really, really hot day. So it was a whiplash as far as temperatures are concerned.

• 7:15Speaker 02

  And then, over the course of the next couple of weeks, all through October, less and less tarantulas, until I was literally out there finding frozen tarantulas on the ground in the mornings.

• 7:29Emily Kwong?

  What is the leading reason, you think, that the cold is correlated to this movement?

• 7:35Speaker 02

  Yeah, what I think is happening, if I wanted to like, kind of anthropomorphize them a little bit, is that they're sitting in there in the sweltering heat going, "I do not want to come out of this burrow. It is so hot." And then, it gets really cold very quickly, and it's making them go, "Oh no, I gotta go find a mate. I'm sexually mature. This is my last hurrah." Male tarantulas actually die after they've sexually matured within about a year. So this is quite literally their last hurrah. And that cold snap is kicking them in the butts.

• 8:14Emily Kwong?

  Yeah. Just to close out the life cycles of tarantula a little bit, once these males find their lady and they mate, what happens to them?

• 8:22Speaker 02

  So, if you're a male tarantula, ideally what you want to happen is you mate,

• 8:29Speaker 02

  and then you're able to skedaddle, get out of there as quick as possible, and go find another female. Unfortunately, as the mating season goes on, the males are using more and more of their reserve energy. Typically during a mating season, males aren't really eating or even drinking. And they get weaker and weaker, and eventually, if they are mating pretty regularly and successfully, they're a little too slow on the draw, and the female decides that she wants a nice dinner to go along with the date. And she clamps down on the male. We also tracked males. You put this little tiny radio transmitter on their backs, and

• 9:15Speaker 02

  we quickly found that it was pretty hard to track them down because they would be half-eaten inside the female's burrow.

• 9:23Emily Kwong?

  What a way to go.

• 9:24Speaker 02

  And we'd have to dig up the burrow to get our... yeah, we'd have to dig up their burrows to get the transmitter back. And then, you know, make it a little bit nice for the female again, so we're not destroying her home.

• 9:36Emily Kwong?

  So after doing your master's thesis, I imagine your appreciation of tarantulas has only deepened. And I want to pass that along to our listeners. What role do tarantulas play in their ecosystems?

• 9:47Speaker 02

  Yeah, so we don't know what we don't know. These tarantulas could be contributing quite a lot to their ecosystems, but we don't even know what's triggering their mating season. As soon as you start bringing up tarantulas, the question then becomes, well, do we really care about them? What are they actually doing? And the answer is, we really don't know. There's a book written in the 1950s called The Tarantula that points out this lack of information. And it is a wonderful little read. It is full of old timey science lingo. And since then, we still lack the majority of that information.

• 10:29Emily Kwong?

  You know, I'm struck by the date of this book, too, because the movie, the horror movie Tarantula came out in 1955. And I'm just wondering, why do you think we know so little about tarantulas? Because some of this stuff does seem very basic.

• 10:44Speaker 02

  Yeah, and I think what it is, if you'll allow me to get on a slight soapbox here.

• 10:52Emily Kwong?

  Oh, please.

• 10:52Speaker 02

  I think what it is, is just cultural ideas of tarantulas and their importance. You know, people love birding in their backyards. We set up bird feeders and things like that. People love hearing about, you know, anything that's big and fuzzy. Tarantulas have this scare factor. And I just like to point out that tarantulas are little and fuzzy, you know?

• 11:18Speaker 02

  But because there's been this push a lot more recently, I think, where people are starting to love, whether it's ironic or not, you know, the creepy crawlies, the outcasts, you know, the roly-poly's are getting a lot more popular, things like bats. Bats have had a huge cultural shift over the past, you know, two decades. They went from being the scary creatures of the night that Dracula called to being people affected. Actually calling them sky puppies and things like that. And I think we're seeing that with a lot of other creepy crawlies like tarantulas.

• 11:53Emily Kwong?

  There clearly has been a major shift. Yeah, and it's a no doubt because of scientists like yourself providing this information. So now that we know that these tarantulas need a cold snap to trigger their mating behavior, how are you feeling about climate change?

• 12:09Speaker 02

  Yeah, and so one of the aspects of my research that I deliberately chose was the population that I looked at near La Junta, Colorado, is on the northernmost edge of this species range. And we often find that these edge populations act as like a stronghold for that species because they're subject to more climatic variations. And so as climate change starts warming these areas up, or we start just seeing much different climatic variation, I would expect that this group of tarantulas actually ends up being

• 12:50Speaker 02

  able to be that stronghold for the species because they're used to such swings in temperature. That's my speculation, without more so knowing basic life history about them.

• 13:05Emily Kwong?

  Dallas, thank you so much for coming on the show.

• 13:07Speaker 02

  Thank you very much for having me. I appreciate it.

• 13:12Emily Kwong?

  Shortwavers, myself and the team have been creating episodes for you for almost six years. And now we have a small but important favor to ask. Can you share your favorite episode of Short Wave with a friend, or a coworker, or a lover, or a frenemy? We really just want to grow the show. And the thing that will help us do that is word of mouth. Tell them to follow us on their favorite podcasting platform, and you should do the same. This episode was produced by Burleigh McCoy. It was edited by our showrunner Rebecca Ramirez and fact-checked by Tyler Jones. Robert Rodriguez was the audio engineer. Beth Donovan is our senior director, and Colin Campbell is our senior vice president of podcasting strategy. I'm Emily Kwong. Thank you for listening to Short Wave from NPR.

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