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Consider: the Kaua'i Cave Wolf Spider

Updated: Jul 2, 2023

A belated Happy Halloween! In honor of the most badass of American holidays, I have a new article here for you on a particularly-spooky creature. If you haven’t figured out from the title, this article is about a spider, so cw: arachnophobia.


Are you afraid of spiders?


There’s a pretty good chance that you are. Studies conducted by the Swiss Archive for Neurology, Psychiatry, and Psychotherapy have found that between 3% and 15% of humans experience arachnophobia, the irrational fear of spiders. While many of us feel our skin crawl when we see a particularly nasty-looking arachnid, some people with arachnophobia take this to the extreme. They cannot look at or even think about spiders without panicking. Many factors influence why humans fear arachnids: their bulbous bodies, their many dead-looking eyes, their fangs dripping with venom. The most frequent source of arachnophobia, though, is how spiders move, that irregular, jerky crawl that seems to stop or start in an instant. Something just looks so unnatural about the way a spider’s legs move. It looks less like the smooth motion of an animal and more like the rough jerk of a marionette.

Scientific evidence suggests that human vision has evolved to pick out spiders from an image more quickly than other, non-threatening stimuli. This makes sense to a certain degree—spiders can be dangerous. The venom of an Australian Funnel Web Spider, for example, causes vomiting, nausea, high blood pressure, and, in some extreme cases, fluid buildup in the lungs leading to death. The Brazilian Wandering Spider’s venom is even worse. This extremely aggressive spider’s venom is neurotoxic, disabling the victim’s nerve cells and causing often-fatal heart palpitations. The Wandering Spider’s venom also gives men priapism, a condition that Matthew Inman (of The Oatmeal) once accurately put as “an erection until you are dead.” If Viagra isn’t working for you, I know a guy in Brazil…

In this article, I am going to tell you about one of the rarest spiders in the world. It is native to caves carved by searing-hot lava flowing beneath the surface of Hawaii. As a troglobite, it has many adaptations that help it to survive in caves, excelling where almost any other animal would starve. You still have to worry about its bulbous shape, its venom, and its erratic motion, but you don’t have to worry about its eyes—because it doesn’t have any. Consider: the Kaua'i Cave Wolf Spider, Adelocosa anops.


Image Credit: Gordon Smith, US Fish and Wildlife Service (Public Domain).

The Kaua'i Cave Wolf Spider is native to the Hawaiian Island of Kaua’i (Kow-eye-ee). Even within Kaua’i, these spiders are only found in lava tubes within the Koloa (Koh-low-uh) Basin, a 4 square kilometer area on the island’s southernmost point. In addition to being the geologic formation with the most badass name, lava tubes are tunnels dug beneath the Earth during a volcanic eruption. Fast-flowing channels of molten lava literally dig beneath the ground, carving out a tunnel which then remains once the eruption has concluded and the lava has gone off to ruin some other landmass’s day. Some of these tubes are large enough for a human to stand in, but others are tiny fissures in the rocks too narrow to explore. The spiders live in both the large and tiny lava tubes, making their habitats difficult to study.

The spiders themselves are pretty small, only about as wide as a US penny (1.9 cm) at their largest. They have amber-colored bodies with pale white abdomens and dark-colored legs. They have no eyes and are completely blind. Despite this, these spiders are able to find one another and capture prey because they have excellent Spider Senses, literally. All spiders are covered in trichobothria: fine hairs that vibrate in response to sounds or other disturbances in the air. These hairs are extremely sensitive and are able to pick up vibrations with an amplitude of less than 1/10,000,000,000th of a meter (about the size of an atom). This allows a spider’s entire body to act like a microphone, picking up any disturbances in the air and transmitting them to the nervous system. It’s not exactly Spiderman's sixth sense, but it’s pretty damn close. The trichobothria of Kaua'i Cave Wolf Spiders’ bodies are particularly long, making them even more sensitive to vibrations than other species. This compensates for their lack of eyes and allows them to navigate their subterranean homes easily.

Being able to sense in the dark is important for Kaua'i Cave Wolf Spiders, as they hunt actively. Wolf spiders in general behave this way, ambushing or chasing prey for short distances, then injecting them with venom. Kaua'i Cave Wolf Spiders primarily hunt Kaua’i Cave Amphipods, another endangered species native to the same area. As far as we know, this is all the spider eats, save for occasional insects that wander into the lava tubes. While the Kaua’i Cave Wolf Spider’s venom is deadly to its prey, the stuff is basically harmless to humans, causing about as much swelling and irritation as a bee sting. Unlike orb-weaving spiders (the common web-builders that you see all the time), wolf spiders do not spin webs. Instead, they dig tube-shaped burrows lined with silk, like cave spider mobs in Minecraft.

Like many spiders, Kaua'i Cave Wolf Spiders breed polygamously, with one female mating with many males before laying eggs. For about a month, the female does this, mating with many different males to ensure that her babies are genetically-diverse. Once her month of sex, drugs, and rock n’ roll has concluded, the female Kaua'i Cave Wolf Spider spider lays 15-30 eggs, a fairly low number for a wolf spider. These spiders probably lay so few eggs at a time because of the scarcity of their environment; there isn’t much for them to eat in the lava tubes, so having a few healthy babies is better for the species' survival in the long run. The female wads those eggs into a sac of silk and sticks it to her abdomen, like a baby bjorn she wears on her ass. Once the babies are born, the mother carries them around on her back for several days, protecting them from predators and ensuring their safety until they are old enough to fend for themselves. This kind of parenting behavior is common in other wolf spider species, but is still rare as a whole amongst invertebrates.


After they are born, baby Kaua'i Cave Wolf Spiders hang out on their mom's backs for a few days while they grow enough to fend for themselves. Do you think babies that are in timeout have to sit by the ass? Only seems fair. Image credit: US Fish and Wildlife Service (USFWS).

Due to their pretty selective habitat requirements and their tiny geographic distribution, Kaua'i Cave Wolf Spiders are extraordinarily rare. No more than 41 of these spiders and 90 of their amphipod prey have ever been encountered. It is possible that this low number is sampling bias, as these spiders often live in very narrow crevices within lava tubes that humans can’t really study or caves that are inaccessible from the surface. Still, the spider only lives in specific caves within a specific area of one island, and they require their lava tubes to stay very humid. If the tubes dry out, the spiders will abandon the cave. As a result, the species’ entire geographic distribution (about 4 square kilometers) has a smaller area than the US Capitol building.

Several factors have contributed to the endangerment of this species. Human land development near the lava tubes has caused changes to their internal conditions that bode poorly for the spider. Agricultural and industrial runoff has led to chemical pollutants entering the caves, and the planting of invasive crops has reduced the humidity within. Like our friend the Olm, cave species like the Kaua’i Cave Wolf Spider are very sensitive to their environments, and even small changes in the weather of their caves can have devastating consequences. Making things worse, all of the caves in which these spiders live are on private property, limiting the kinds of regulations that the US Fish and Wildlife Service (FWS) can use to protect the species. While FWS researchers have been able to investigate some of the lava tubes, they have been barred from entering others in areas where the property owners have not permitted them to go.

In recent news, a building project by Meridian Pacific (a real estate development company) has brought yet another potential threat to the spiders’ habitats. The company is developing luxury condominiums in Koloa in an area of the region believed by FWS to contain inaccessible underground caves where Kaua’i Cave Wolf Spiders may live. In addition to threatening populations of these spiders, the construction could potentially disturb burial sites in the Koloa region which are sacred to the local indigenous people. As such, many indigenous advocacy groups, such as Save Koloa and Friends of Maha’ulepu, have sought a legal injunction to prevent the condos from being built. Many indigenous people in the area feel that Meridian Pacific’s development projects threaten their way of life by catering to tourists and disregarding the deep connection the people of Koloa have to the land their ancestors have lived on for generations.

Hope is not lost for this tiny, eyeless, hairy critter. Despite the challenges to its conservation, progress has been made to protect the Kaua’i Cave Wolf Spider from extinction. Researchers from FWS have installed airlock mechanisms at the mouths of the lava tubes in which the spiders live, increasing the humidity inside so that the spiders and their prey can return. The restoration of native plant species has also helped contribute to this humidity increase. Thanks to this, the population of Kaua’i Cave Wolf Spiders has increased in several caves, and juvenile spiders were recently observed for the first time.

I think the plight of the Kaua’i Cave Wolf Spider highlights how interconnected conservation is to many other modern issues. Large corporations and the agricultural industry have the potential to create great abundance, but left to their own devices, can trample ecosystems and indigenous cultures alike. When land is cleared for real estate development or rainforests are chopped down for agricultural space (as is the case in the Western Ghats, home of the Indian Purple Frog), the indigenous people who have relied on this land to survive for millennia are often forced out. The Meridian Pacific project will convert a significant portion of the land in Koloa to be used for luxury tourism, displacing the local ecosystem and preventing local indigenous people from using the land. Adding insult to injury, these luxury condos are being built amidst a housing crisis that has caused many native Hawaiians to struggle to pay their bills. According to the National Low Income Housing Coalition, 20% of Hawaiians live at or below their local poverty guideline, and 66% of those people spend half or more of their income on housing. Yet, land developers like Meridian Pacific continue to construct multi-million dollar condominiums in their backyards, degrading the local ecosystem and slapping the local people struggling to pay their bills in the face.

Protecting endangered species is going to require human society to think long and hard about how to use the land we have. If we choose to use land selfishly, demolishing ecosystems for real estate development and urban sprawl, we will not only lose thousands of unique and wonderful creatures like the Kaua’i Cave Wolf Spider, but we will also exterminate the indigenous cultures to whom those ecosystems have belonged for generations. We don’t have to live this way. We can choose to use our land wisely, to consider the perspectives of the vulnerable creatures within it and the people whose cultures are linked to it. We can use our resources not just to amass wealth for a few, but to uplift all of the living things that we share this planet with.

Kaua’i Cave Wolf Spiders are a weird animals. They live in a very particular and rare ecosystem, navigate exclusively through touch, and are one of a very select group of invertebrate species that care for their young. These spiders’ pickiness when it comes to habitat makes it a real challenge to study and protect, but yet conservationists have made real progress in protecting them. If we as a society can protect a creature as strange and particular as the Kaua’i Cave Wolf Spider from extinction, it will be a sign that we are willing to use this planet’s land responsibly and protect the interests of all its many inhabitants.


Click here to learn more about Save Koloa and their organization's efforts to protect the Kaua'i Cave Wolf Spider. If you have the money, consider donating to help protect this rare and amazing species as well as the indigenous culture of Koloa.


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