Tarantulas: Reproduction

Summary: Making babies isn’t easy for tarantulas! So many steps go into creating tarantula spiderlings. Join Kiersten as she talks you through this fascinating behavior.

 

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

 

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 seventh thing I like about tarantulas is how they reproduce!

I’m sure you have all heard at least one thing about spider reproduction before listening to this podcast episode and I’m sure it’s the rumor that male spiders better run fast after mating or they’ll get eaten! That can be a valid concern with various species of spiders and even some tarantulas, but not all female spiders are out there looking for a good man to eat. 

Before the male finds himself in this precarious situation there are many steps he must perform first. Let’s start at the beginning. Mating season for many tarantulas is in the late summer or early fall. This is when those of us that live in the western United States will encounter male tarantulas in the road, yards, or even our houses. They are out looking for females.

Before they leave their burrows though, they have a bit of work to do to get ready to win over the ladies. Males must charge their palpal bulbs on the ends of their pedipalps with sperm before they wander out to find a female mate. What exactly does that mean? Great question and I have one doozy of an answer! 

To be able to mate with a female the male tarantula must have a way to transfer his sperm to the female so that her eggs can be fertilized and grow into baby tarantulas, or spiderlings. The male tarantula uses the palpal bulbs, which are hardened sperm storage organs on their pedipalps to make that transfer.  His sperm is made inside his body but not near the pedipalps; therefore, he has to complete a rather long process to get his sperm just where he wants. 

First the male spins a blanket of silk somewhere in his burrow or a protected area at an angle, then he spreads his sperm on the underside of the silk blanket, or sperm web. Next he maneuvers himself on top of the web in just the right spot so that he can reach the sperm with his pedipalps and dips the palpal bulbs into the sperm drawing it into this storage organ. Whew! I’m worn out just talking about all that work. 

Once he’s all charged up, he’s on the prowl. Most females stay in or near their burrows or nests their entire lives, so the male has to go hunting. Now he doesn't just charge into a female’s burrow, that’s how you get eaten! So how do you get a female to come out of their deep, dark hole without losing your life? You dazzle her with song!

Male tarantulas will drum their front legs on the ground just outside the burrow or on the silk threads that protrude outside the female’s burrow. This is how they let the female know it is a romantic house call. This is risky for the male because if the female is not receptive to mating she could come out and aggressively run him off or even damage him. He might also mistakenly pick a male’s burrow. Males don’t generally get into fierce fights with an accidental courting but it’s precious time wasted. 

To help streamline things, females will often announce their receptiveness by applying a pheromone on the silk outside their burrow that let’s males know to knock on her door. Some species of tarantula will actually place this pheromone web in plant matter above their burrow so that the wind will blow the scent farther. Then the male will come and the drumming will commence.

If the female is interested, she will emerge from the burrow to inspect her suitor. Once they are face to face there are a few things that can happen. If she needs a bit more persuading, the male will begin a dance with his front legs, lifting them up and down. Sometimes the female will join in the dance and sometimes she just moves towards the male immediately. Responses can vary from species to species but can also vary with individuals in the same species.

Once he’s won the female’s permission, the slightly dangerous part begins for the male. The two tarantulas will stand in front of each other face to face, then the male with reach under her with his front legs and grasp her fangs with small spurs on the ends of his legs. Once her fangs are secured, which seems like a way for him to make sure she doesn’t try to eat him once copulation is complete, the male will gently lift her and reach back to her genital openings and place his sperm inside. This doesn't take much time and once he’s done he skedaddles as fast as he can.He’s off to find another female. In the wild sexual cannibalism seems to be rare, but in captivity it is known to happen in certain species. 

The female will often fall into an immobile state for several moments after copulation is complete, which is the perfect time for the male to split. We don’t know why the female becomes immobile at this time, but it appears to happen in almost every species of tarantula, at least ever species we’ve observed mating.

Now the female will usually carry the sperm in her body until she is ready to create an egg sac. Since mating is in late summer or early fall, she will typically carry the sperm around until the following spring or summer. Then she prepares some silk and lays the eggs in the silk. The eggs are fertilized with sperm as she lays them. She then rolls the silk into a sturdy egg sac. Depending on the species, she will either carry the sac around with her or stash it safely in her hideout. Generally speaking, ground dwelling tarantulas seem to be the ones that carry the egg sac around while arboreal species leave them in the safety of their homes. This may be due to the fact that the eggs must be kept warm so they can grow into spiderlings and burrows underground stay cooler than nests in trees. Maybe. 

Depending on the species, females can lay anywhere from twenty to one thousand eggs. That’s a whole lotta babies! The eggs typically incubate from 2 to 3 weeks before they hatch. During incubation mom takes very good care of her eggs sac. If she is a species that carries the sac around she’s constantly monitoring the temperature to ensure the eggs do not get too hot or too cold. If they secure them in a hidden space, she’s always nearby making sure the egg sac is safe. 

When it’s time to hatch, the spiderlings will either emerge after they have molted into their first instar stage or before. When they do hatch, they’ll be about the size of a tick. In Avicularia species the spiderlings will emerge in their first instar stage after their first molt. They will be covered in a dark, hairy, hard exoskeleton and will be fully mobile. Other species will emerge as pale, soft nymphs without a hardened exoskeleton. After a few weeks the nymphs will molt into their first instar stage. The spiderlings will hang out with mom for a few weeks and then head out into the world on their own. 

Many people think tarantulas are bad moms and that it’s get out or be eaten as soon as you hatch, but some researchers at Hiram College studying an East African tarantula species saw something quite different. The researchers were actually studying these tarantulas’ breeding behaviors, which were successful, giving the researchers a whole other exciting behavior to study.  After the spiderlings hatched the researchers fed the mother and the babies some crickets and saw something remarkable. The mother grabbed a cricket and allowed many of her spiderlngs to gather around her mouth and share the meal with her, while a second cricket was shared by the rest of the spiderlings! 

I think this is some truly amazing and unexpected behavior. It’s also something that we share in common with this tarantula, caring for young and sharing with our siblings! Who woulda thought?

Like many invertebrates tarantulas must molt their exoskeleton to grow. This can be a complicated and dangerous moment in the tarantulas life. To molt they must crack open their current exoskeleton, flip over on their backs, and shimmy out of their old clothes. It takes several hours until their new exoskeleton hardens and while they wait they are vulnerable. But this it what tarantulas must do at least once a year until they are fully mature and ready to make their own babies. 

The age of maturation varies greatly amongst tarantula species. Some females can take up to ten years before they are ready to mate. Many females of various species can live twenty to thirty years. Males mature earlier and generally live a lot shorter lives than females. Sorry about that guys.

Well, that’s all there is for tarantula reproduction. I hope you were as fascinated by this behavior as I was because it’s my seventh favorite thing about them. 

If you're enjoying this podcast please recommend me to friends and family and take a moment to give me a rating on whatever platform your listening. It will help me reach more listeners and give the animals I talk about an even better chance at change. 

 

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.