Eaten, Crushed or Starved; Male Tarantulas Trade Their Life to Impregnate a Mate

Eaten, Crushed or Starved; Male Tarantulas Trade Their Life to Impregnate a Mate

On an early evening in September, 16 dark, hairy legs were kicking up dust on the prairie floor in La Junta, Colo. A male Oklahoma brown tarantula was locked in a heated mating match with a female twice his age. Although weary, he plunged a set of hooks that had recently grown on his front legs into his mate’s mouth, just below her glossy fangs, to prevent her from chewing him up.

The intense ritual was taking place across the arid grasslands of southeastern Colorado, where the tarantula mating season spans September. Female tarantulas can live multiple decades and never travel more than a few inches from their burrows. Males mature in seven to 10 years, and when they finally venture beyond their burrows, they have only one goal—mate—and then their life’s job is done.

“They weren’t evolved to survive,” says entomologist Maia Holmes, education and outreach coordinator at the department of agricultural biology at Colorado State University. “They are at the end of their life cycles, and this is their last hurrah.” Similar fates await male tarantulas in other western U.S. states, in Central and South America, and around the world.

Using a specialized appendage near his mouth called a pedipalp, the male spider reached forward and carefully slid a packet of sperm into the female’s abdominal cavity. The package contained enough sperm to fertilize upward of 1,500 eggs. Typically only a few spiders from a clutch of hundreds survive into adulthood; offspring only need to replace their parents to sustain a population.

Once our male—let’s call him Spiderman—carefully extracted his hooks from his mate’s fangs, he dropped to the ground and scurried backward while the female was still reared up like a horse on her hind legs. All tarantulas are nearly blind their whole life, so he was fleeing by feel.

Spiderman might have tried to mate again, if he could summon the energy. But in the following weeks only one thing was certain: he would perish. Spiderman didn’t die like his father may have: eaten head-first by his female mate. Both ravenous and bold, the mother would strike the father’s head with her venom as soon as he finished gifting his sperm and immediately take a bite from his left “temple.” Spiderman had picked a mate who, luckily for him, had recently eaten.

Our protagonist didn’t die like his brother may have either. The sibling, let’s call him Brother, was taken captive by a tarantula hawk, a massive spider wasp that grows to two inches long. Tarantula hawks are pollinators, sampling nectar from flowering plants, but when it’s time to raise their young, the females of the species take on a different demeanor.

Brother had just stopped to rest on a quiet patch of dirt when he was attacked. For several minutes the wasp circled him, flitting in and out with the agile prodding of a fencer. Brother did what most tarantulas do when they feel threatened: he froze. The wasp turned upside down and maneuvered under Brother’s abdomen to search for a soft spot, like a mechanic sliding under the chassis of a car, and injected his paralyzing venom there.

The tarantula hawk dragged his paralyzed but living prey into Brother’s own den and laid a single egg on his abdomen. Over the next couple of weeks, the egg hatched, and the developing insect that emerged ate its way through Brother’s tissues, saving vital organs for last so that he stayed alive and fresh, though starved, for as long as possible.

Fortunately, Spiderman also didn’t die like any number of his cousins—crushed by a semitruck while scrambling across a street in search of a mate. Moments before they die this way, the poor-sighted tarantulas can sense a vehicle’s vibrations through their highly sensitive paws on the pavement, but by then it’s too late. And as habitat fragmentation continues, and humans’ footprint on the landscape widens, this fate will become increasingly common.

Our Spiderman died a slower death. After mating, he lost interest in food. He became weak because the majority of his energy reserves went to sperm production. He managed to avoid tarantula hawks and roads. But as he continued to lose energy, his body became slower, more rigid. The blood pressure generated from his heartbeat slowed, causing his legs to curl inward—what’s known in the spider world as the “death curl.” It was also time for him to molt his exoskeleton, an impossible feat that sealed his fate. “Molting is like pulling yourself from a suit of armor without using your hands,” Holmes says. “And for a male spider who has mated, his hooks and reproductive parts prevent his molt from sliding off. They get stuck.”

As the hours went on, Spiderman twitched less. He stopped fighting. And as he lay there, curled up beside a halo of small yellow flowers—perhaps the very flowers pollinated by the wasp that killed his brother—he had no idea of the impact he had on the world. He had no idea that his position as a key predator in his ecosystem helped manage its insect population, no idea that his eight-legged form inspired robotic technology and innovations in artificial webbing and no idea of the future that a changing planet might have in store for his descendants.

Researchers are trying to understand what climate change might do to tarantula populations. As temperatures warm, and flowers’ growing season extends later into the year, the pollinating tarantula hawks might be out later. Male tarantulas might be mating at a time when more wasps—more threats—are around, explains Richard Reading, vice president of science and conservation at an invertebrate zoo called the Butterfly Pavilion in Denver and an adjunct professor at the University of Denver. “Tarantulas also have a mechanical system to their movement; heat impacts that, too,” Reading says.

Back in La Junta, Spiderman’s own mechanics were failing. In these final moments, his partially shed exoskeleton blocked his book lungs—delicate, platelike structures that allowed air to enter his body passively. He was running out of energy and now oxygen. But just moments before he faded away, a bushy-tailed Swift Fox no bigger than a house cat swiped him up and gobbled him.

In these grasslands, tarantulas are both prey for numerous species and top predators, crucial to keeping the insect populations at bay and the ecology in balance. “All creatures serve a purpose in the web of life. Every species contributes to the stability of an ecosystem,” Reading says.

The fox wandered into the night as the sun set over the dusty hills of La Junta, perhaps trotting over the very burrow that housed the female who now held the future of Spiderman’s bloodline. As humans, we often anthropomorphize the animal kingdom, and some of us may feel pity for our central character. But “there are no good guys or bad guys in nature–it’s all interconnected,” Holmes says. “Everything needs to exist for everything else to exist.”

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