Smart Spiders
Why do people often think animals need big brains to be smart?
What makes jumping spiders different from web-building spiders?
Why are Portia spiders considered especially smart?
What does Portia do when hunting Euryattus spiders?
How does Portia fool web-building spiders?
What did the experiment with the tall towers show about Portia?
How did scientists test if Portia can be surprised?
What happened when the number of prey changed?
Why did Portia sometimes choose a longer escape path?
What does this article suggest about small animals with small brains?
How Tiny Brains Can Do Big Things
Most people think that animals need big brains to be smart.
Humans, chimpanzees, and dolphins all have large brains, and we know they can do amazing things. But scientists are learning that even animals with tiny brains—like spiders—can be surprisingly clever.
For a long time, people believed that small animals couldn’t do complex thinking.
But many animals on Earth are tiny, and we haven’t studied most of them closely. Now, scientists are paying more attention to spiders and discovering that these little creatures are much smarter than we ever thought.
“IT’S NOT ABOUT BRAIN SIZE”
Dr. Dimitar Dimitrov, a spider expert in Norway, says that spiders challenge the idea that brain size always shows how smart an animal is. Even though they’re small, spiders are showing signs of learning, decision-making, and even planning.
Some spiders, like orb weavers, change the way they build their webs depending on what kind of bugs they catch. Other spiders, like ghost spiders, can learn to connect a smell—like vanilla—with a reward. These are not just automatic behaviors.
They show that spiders can think and learn.
Dr. Fiona Cross from New Zealand says, “It’s not about brain size—it’s about what the animal can do with the brain it has.”
The Smartest Spiders of All
Among all the spider species, jumping spiders seem to be the most intelligent.
Their brains are tiny—smaller than a poppy seed—but what they can do is amazing. If a dog or a toddler acted like a jumping spider, we would think it was very smart.
Jumping spiders don’t wait in webs for food.
Instead, they use their excellent eyesight to look for prey.
Some are only a few millimeters long, but they can see very well and spot things from far away. Because they’re always on the move, they need to look out for food, mates, and danger.
Scientists think this is one reason jumping spiders have developed such strong thinking skills.
Tricky Hunters
Some of the cleverest spiders are in a group called Portia.
These jumping spiders live in Africa, Asia, and Australia. They hunt other spiders, which can be dangerous. So they use smart tricks to catch them.
For example, when hunting a spider called Euryattus, the Portia spider copies the way a male Euryattus shakes a female’s nest.
The female comes out expecting a mate—but instead, she finds Portia, who is ready to pounce.
Portia also fools web-building spiders by plucking their webs in different ways.
If the prey is small, Portia makes the web vibrate like there’s a trapped bug. The other spider rushes over and—surprise—it becomes lunch.
If the spider is bigger, Portia makes gentler movements so the prey doesn’t get alarmed.
If nothing works, Portia tries shaking the whole web like the wind, so it can sneak inside unnoticed.
In the lab, scientists saw that Portia keeps testing different ways to pluck the web until it finds the one that works. It’s like the spider is learning what trick will fool each prey.
Planning Ahead
One amazing skill Portia spiders have is the ability to plan.
In the wild, they have been seen spotting prey from far away and then taking a long, roundabout path to get closer. Sometimes they sneak above the web and drop down on silk without touching it.
In one experiment, scientists put a Portia spider on a tall tower with two other towers in sight—one with a box containing a dead spider (a meal) and one with a box of leaves.
The spider had to climb down and choose the right walkway to reach the prey without falling in water.
Most of the time, the spider picked the correct path—even when it meant walking away from the meal first. That showed the spider made a plan from the top and followed it.
That’s a big deal for a spider with a tiny brain.
Expecting the Unexpected
To test how Portia thinks, scientists used a trick from baby psychology. Babies look longer at things that surprise them. So scientists showed Portia one kind of prey, then quickly swapped it for another when the spider wasn’t looking.
When the spider saw a different prey than it expected, it was less likely to attack. That meant it remembered what it saw before and got confused when things changed. This kind of thinking is called “mental representation”—it’s when an animal can picture something in its mind.
Spiders That Can Count
Portia can also notice numbers. In another experiment, scientists showed a spider one prey item, then later showed two or three. The spider was less likely to attack when the number of prey had changed. It seemed to expect the number to stay the same.
Even though spiders can’t count like we do, they can tell the difference between “one,” “two,” and “many.” That’s about the same number sense as a one-year-old human.
Making Smart Escapes
Being a jumping spider is dangerous.
Birds, ants, frogs, and even other spiders want to eat them. So jumping spiders need to know how to escape safely.
In one test, scientists put a spider on a platform in the middle of a tray of water. The spider had to jump across little wooden posts to reach safety.
Spiders hate water, so they wanted to pick the safest path. Most of the time, Portia picked the path with the fewest jumps. But sometimes, the spider chose a longer path and skipped over some posts to make it shorter.
That meant the spider found a shortcut the scientists didn’t even think about!
Portia takes its time, too. While other spiders rush, Portia often waits and studies the path before moving. That careful thinking seems to help it make better decisions.
Smarter Than We Thought
Scientists are still learning what spiders like Portia can do. There may be many other small animals with big thinking skills.
Just because a brain is small doesn’t mean it can’t do amazing things. In fact, the more we study spiders, the more we see just how clever they really are.
Arachnid – A group of animals that includes spiders, with eight legs and no wings or antennae.
Cognition – The process of thinking, learning, and understanding.
Prey – An animal that is hunted and eaten by another animal.
Representation – A mental picture or idea of something.
Experiment – A scientific test to learn how something works.
Mental – Having to do with the mind or thinking.
Strategy – A careful plan to reach a goal.
Predator – An animal that hunts other animals for food.
Ambush – A surprise attack.
Observation – The act of watching something carefully.
► COMPREHENSION QUESTIONS
— please answer with complete sentences
Why do people often think animals need big brains to be smart?
What makes jumping spiders different from web-building spiders?
Why are Portia spiders considered especially smart?
What does Portia do when hunting Euryattus spiders?
How does Portia fool web-building spiders?
What did the experiment with the tall towers show about Portia?
How did scientists test if Portia can be surprised?
What happened when the number of prey changed?
Why did Portia sometimes choose a longer escape path?
What does this article suggest about small animals with small brains?