Orbs, Tangles, and Sheets: Spider Web Styles Linked to Anti-Predator Adaptations

12 days ago

Spiders build webs to catch food, but some webs protect them better than others. A recent study discovered that spiders in webs that make them easy targets for predators are usually brightly colored, have armor, or use camouflage. On the other hand, spiders in more secure webs tend to have plain colors. This suggests that there is a balance between web design and other ways spiders protect themselves from predators. The image shows a tangle-style web, which provides more protection compared to flat, two-dimensional orb-style webs. (Image courtesy of João Burini, www.primalshutter.com)

Spider - Figure 1 — Photo Entomology Today

Written by Dr. Grant Bolton.

We are constantly amazed by the impressive creations of architects, who effortlessly merge art and practicality to construct stunning buildings that last for generations. However, in the serene beauty of nature, spiders have been skillfully weaving intricate webs for millennia. These small yet highly skilled builders create their webs not only to capture food but also to outsmart potential threats in a high-stakes game of survival.

In the ecosystem, arthropods are usually found at the bottom of the food chain. Spiders, while they hunt and feed on other animals, also fall into this category. For birds, lizards, and wasps, web-building spiders could be seen as an easy meal, as they are often found waiting in the center of their webs.

Yet, spiders have created defenses against predators in order to survive, such as their web-building techniques. These webs require a significant amount of energy and resources. The specific type of web a spider creates may impact their ability to efficiently allocate resources and adapt physically.

Web Architecture's Importance In Avoiding Predators

A recent research article in Insect Systematics and Diversity, published in August, delves into the various types of webs that spiders create and how they impact their ability to avoid being eaten by predators. The most common spider web design is flat and on one level, known as a two-dimensional (2D) web. These webs may or may not include a shelter for the spider to hide in. This shelter can act as a diversion or disguise, resembling trash caught in the web.

However, there is a different type of spider web that many spider species use. Known as tangles or sheet-and-tangles, these three-dimensional (3D) designs are often ignored by researchers and the public. These 3D structures provide space for the spider to hide within the inner web and offer better protection than a 2D web design. They may also include a refuge for the spider.

Can varying website designs impact how animals defend themselves against predators and their chances of getting attacked?

Leticia Avilés, who holds a Ph.D., is a scientist and teacher in the Zoology Department at the University of British Columbia. She is the main writer of the new research. Past studies have shown that 3D webs can help protect against being hunted. This discovery led Avilés and her team at UBC and the Instituto Butantan in Brazil to explore if these webs' added protection could mean less need for other defenses against predators.

The changes that spiders make, like using bright colors or spikes, hiding or behaving in a certain way, are very important for spiders to survive. Scientists believed that the way a spider builds its web could affect the need for these changes. They thought that spiders in flat webs, which are out in the open more, would spend more energy on these anti-predator tactics. On the other hand, spiders in more sheltered 3D webs might not need to use as many of these tactics. This idea made scientists want to study how the shape of a spider's web affects these adaptations more closely.

Web-Building Strategies Tradeoffs

Andrea Haberkern, a doctoral candidate at UBC who led the study, and also the creator of the well-known Facebook group "Spider/Bug Questions With TheBugGirl", noted that spiders must make important choices depending on the design of their webs.

"In 3D web builders, there are expensive structures that require a lot of investment, so they may not prioritize other adaptations as much. It's similar to owning a home versus renting," according to Haberkern. "With a less costly 2D web, you are more exposed and vulnerable to predators, increasing the likelihood of your web being destroyed by larger animals. A spider in a 2D web would benefit more from anti-predator adaptations than one investing resources in building a more protected 3D web."

The results of their research indicate that spiders that are brightly colored and have hard shells are usually found in flat spider webs without a hiding spot, whereas spiders that can blend in with their surroundings are often found in flat webs with a hiding spot. On the other hand, spiders that make 3D webs are usually a neutral color.

Haberkern thought back on her time exploring the rainforests of Ecuador to discover these spiders that build webs in both 2D and 3D. "I had to carefully approach the spiders, study them, and see how they reacted," she recalls. "And it turned out that the 3D web-building spiders tended to be less aggressive and would usually run away if their webs were disturbed by a predator."

Avilés explains that animals have various ways to protect themselves from being hunted, such as hiding, remaining motionless, or camouflaging. On the other hand, some spiders are brightly colored as a warning signal to predators that they are dangerous.

Typically, animals with vibrant colors are thought to be venomous, but they could also be signaling predators about spikes and armor on their bodies. Essentially, they are saying, "I am a threat; do not try to harm me."

Avilés explains that they rated the camouflage level of the objects on a scale ranging from blending in completely with the background to standing out prominently with bright colors. The concept behind this rating system is that bright colors are often associated with danger.

Spiders that build weaker webs are more prone to developing defense mechanisms against predators, like vibrant colors or tough exoskeletons, as shown by this Micrathena schreibersi spider. (Image courtesy of Nicky Bay, www.nickybay.com)

Spiders that build webs that provide less protection are more likely to have ways to protect themselves from predators, like having bright colors or hard shells. This Macracantha arcuata spider is an example of this. (Photo by Nicky Bay, www.nickybay.com)

Survival Strategies Amid Deception

But some types of animals build a hiding spot within their webs. For instance, they gather fallen leaves from the woods and tie them to their webs. This way, they can conceal themselves among the leaves when they sense danger.

Various types of spiders have unique ways of hiding or protecting themselves. For example, certain Cyclosa species will hang their old exoskeletons in a line, making it difficult to identify the real spider among the decoys. This tactic is so convincing that even a closer inspection is needed to uncover the true spider.

She explains that a different type of animal constructs a replica using old materials and prey, shaping it to resemble a spider. When I first observed it, I believed it was random, but it continued to happen repeatedly. Indeed, this spider species forms a realistic copy of itself to deceive predators. The process of evolution is truly astounding!

The changes happening to spiders are not limited to their physical appearance but also extend to their actions. According to Avilés, the webs they create can be seen as an additional part of their characteristics. This is because natural selection plays a role in determining both the shape of the spider and how they construct their webs.

The way spiders design their webs gives us a cool look at how they have changed over time to find a good balance between staying safe from predators and finding food. This research shows how a spider's environment, web, and evolution all work together in a complicated way. By learning about these changes, scientists can learn more about the reasons behind why spiders act and look the way they do.

Grant Bolton, who holds a Ph.D. in insect science, is an independent writer and voiceover artist located in the western part of Missouri. For inquiries, contact him at [email protected].