Ogre-faced spiders can hear low- and high-frequency sounds, according to a new study.
(CNN) -
Scare season is here, so let's talk about spiders.
Ogre-faced spiders are believed to have the largest eyes of all known spider species.
And they are also known for their ability to see in the dark 2,000 times better than humans.
However, that formidable sight is just one of the sensory tools these arachnids can use when searching for food, a new study revealed.
These spiders can hear too.
In fact, ogre-faced spiders can hear both low- and high-frequency sounds, according to the study, which was published Thursday in the journal
Current Biology
.
These spiders, with receptors on their legs, can detect sounds from a distance of at least 20 meters from the source.
And they are sensitive to frequencies up to 10 kilohertz, the research team said.
Through laboratory tests and observations in the field, the scientists demonstrated that auditory stimuli in the same low-frequency range as the flapping of moths, mosquitoes, and flies led the spiders to perform a "backswing," one of his characteristic hunting movements.
This, according to the researchers, showed that spiders use auditory signals to detect and capture flying prey.
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"These spiders are a gold mine of information that has not been exploited for a long time," said study co-author Jay Stafstrom, a postdoctoral researcher in Neurobiology and Behavior at Cornell University.
"The visual capabilities they possess were unknown and now, showing that they can hear quite well, I think there is much more to understand about them in the future," he added.
Like 'Jekyll and Hyde'
Ogre-faced spiders are tropical creatures found throughout the world, including the United States, where they are present in southern states like Florida.
However, it is unlikely that you would have noticed them in your backyard, as they spend the hours of the day camouflaged as plant leaves and only activate at night.
"The metaphor is Jekyll and Hyde," lead study author Ronald Hoy, a professor of neurobiology and behavior at Cornell, told CNN.
During the day, this creature acts as if it were dead.
At night this creature kills, hunts.
Their personality is determined by the sun or the moon, ”he explained.
Dramatic windbreakers
Unlike other spiders that build a web that captures their food, ogre-faced spiders are web-throwers and hunt in a more active, rather dramatic way.
They build an A-shaped net from which they hang upside down at night.
And they use a net that they hold with their legs to catch prey when they are within reach.
Ogre-faced spiders attack forward to capture prey below them and backward to capture prey flying overhead, Stafstrom said.
The two hunting methods are based on different senses, he explained.
"There seems to be this nice division of the sensory systems, where they rely on vision to specifically catch things on the ground, and their ability to hear allows them to catch things from the air," he explained.
Spiders don't have ears, but ogre-faced spiders are able to hear sounds through receptors on their legs, including hairs on their legs, according to the researchers.
Sounds and threat detection
The ogre-faced spiders reacted differently to sounds based on their frequency, the study showed.
The spiders would make their "back strike" to search for food in response to low-frequency sounds in the same range as the flapping of the animals they feed on.
But when they heard high-frequency sounds that matched the range of the birds' songs, they didn't move.
This does not mean that spiders cannot hear high frequency sounds.
Laboratory experiments scientists conducted to monitor spiders' brain activity in response to sounds confirmed that they could, in fact, hear them.
Instead, the scientists suspect that spiders could ignore these sounds in self-defense, something they want to investigate further in the future.
“We know that birds eat a lot of spiders.
I have seen many birds in the palm trees these spiders are found on, and they chirp in the high frequency ranges that these spiders can detect.
So it could be an early warning sign that, well, something might be coming to eat me soon, ”Stafstrom said.
Testing the hearing of spiders
Monitoring spiders' response to auditory stimuli via nanotechnology electrodes inserted into their brains and legs, as the researchers did, is not easy.
The process of inserting electrodes into a spider's brain without killing it requires highly skilled preparatory work and "the hand of a watchmaker," Hoy said.
Today he said that study co-author Gil Menda, a postdoctoral fellow in Cornell's Department of Neurobiology and Behavior, is the one with this special talent.
Developing a method to record spiders' brain activity, Roy explained, allowed the Cornell research team to convincingly demonstrate that spiders are not only sensitive to vibrations, but also to sound from a distant source.
Search for spiders in their natural habitat
The researchers also conducted observations in the field to study the behavior of spiders in their natural habitat.
Hanging out with night spiders in their habitat isn't the most comfortable experience, but Stafstrom does it with passion.
For this study, he spent a week in the woods in Gainesville, Florida, equipped with a headlamp, a Bluetooth speaker to play sounds for the spiders through his smartphone, and a camera to film their reactions.
Stafstrom gained experience in spider camping throughout his studies, for example while doing his Ph.D. at the University of Nebraska - Lincoln.
“I was alone in Florida, in a tent, for two months in the middle of the summer.
It was difficult, my sleep schedule was very strange, but it is definitely the best way to study these spiders, ”he said.
During a field mission in Costa Rica, Stafstrom was bitten by an ogre-faced spider.
"He might hold the world record for being the only person bitten by these spiders," Stafstrom said.
The sting was harmless, he said.
It only stung him for a while.
Spiders and technology
There's still a lot we don't know about spiders, and that's a void we need to fill, according to Hoy and Stafstrom.
Studying how spiders and other small animals can see and hear can drive new discoveries and applications of nanotechnology, the researchers explained.
"If we can figure out what equipment they are using and how they process the information, we should be able to translate that through biomimicry into better biosensors, better directional microphones or visual processing algorithms," Stafstrom said.
"The point is that any group that has been little studied and undervalued has a fascinating life, even a disgusting spider, and we can learn something from them," added Hoy.
Spiders