Basil el Jundi / Lund University
Basil el Jundi / Lund University

Dung Beetles Navigate Using Mental Snapshots of the Sky

Basil el Jundi / Lund University
Basil el Jundi / Lund University

We may giggle about the diet of dung beetles, but these bugs have an awful lot to teach us about animal minds. Researchers have found that dung beetles use mental snapshots of the sky to find their way. The report was published in the journal Current Biology. 

These are the same researchers from Lund University who previously outfitted their dung beetle subjects with tiny vision-blocking hats to determine if the bugs were navigating by sight (they were). Once the scientists realized that the beetles were looking at the sky to get their bearings, they wanted to know how it worked.

The research team, led by Lund University researcher Basil el Jundi, suspected that the navigation process might be associated with the beetle’s habit of climbing atop its dung ball and turning in a circle, a process the researchers call dancing. 

The scientists brought dung beetles (in this case, Scarabaeus lamarcki) into an arena with an artificial sky, which allowed them to manipulate the sources and amount of light the beetles could see. They ran three separate experiments to tests the bugs’ responses to light polarization patterns, gradients of colored light, and different intensities of light—all factors that influence the navigation of other traveling insects like bees and ants. 

In the end, it was all about the dance. Beetles were able to roll their dung balls away in a straight line if they had the opportunity to rotate in a circle while watching the sky. During that time, the researchers say, the insects were taking mental snapshots of the positions of the artificial stars and planets, which they then translated into maps for their movement on Earth. Pretty sophisticated stuff. 

"Other animals and insects also use the position of celestial bodies to navigate,” el Jundi said in a press statement, “but the dung beetles are unique—they are the only ones to take a snapshot where they gather information about how various celestial bodies, such as the Sun, Moon, and stars, are positioned.”

Specialized map-making is not unique to dung beetles. Little fish called frillfin gobies spend much of their lives in tidal pools. When the water level in their pool diminishes, the fish are able to jump into another pool, even though they can’t see where they’re going. Scientists in the 1950s realized that the fish make mental maps of the entire tidepool region as the ocean carries them up and into the pools. The gobies memorize the overhead map, then translate it into ground-level topography to help them decide which way to jump.

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iStock
Crafty Crows Can Build Tools From Memory
iStock
iStock

Scientists have discovered yet another reason to never get on a crow's bad side. According to new research reported by Gizmodo, members of at least one crow species can build tools from memory, rather than just copying the behavior of other crows—adding to the long list of impressive skills that set these corvids apart.

For the new study, published in the journal Scientific Reports, an international team of scientists looked at New Caledonian crows, a species known for its tool usage. New Caledonian crows use sticks to pick grubs out of logs, sometimes stashing these twigs away for later. Tools are so important to their lifestyle that their beaks even evolved to hold them. But how exactly the crows know to use tools—that is, whether the behavior is just an imitation or knowledge passed down through generations—has remained unclear until now.

The researchers set up the experiment by teaching eight crows to drop pieces of paper into a box in exchange for food. The birds eventually learned that they would only be rewarded if they dispensed either large sheets of paper measuring 40-millimeters-by-60 millimeters or smaller sheets that were 15-millimeters-by-25 millimeters. After the crows had adapted and started using sheets of either size, all the paper was taken away from them and replaced with one sheet that was too big for the box.

The crows knew exactly what to do: They ripped up the sheet until it matched one of the two sizes they had used to earn their food before and inserted it into the dispenser. They were able to do this with out looking at the sheets they had used previously, which suggests they had access to a visual memory of the tools. This supports the "mental template matching" theory—a belief among some crow experts that New Caledonian crows can form a mental image of a tool just by watching another crow use it and later recreate the tool on their own, thus passing along the template to other birds including their own offspring.

This is the first time mental template matching has been observed in birds, but anyone familiar with crow intelligence shouldn't be surprised: They've also been known to read traffic lights, recognize faces, nurse grudges, and hold funerals for their dead.

[h/t Gizmodo]

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Jana Mueller
Ravens Can Figure Out When Someone Is Spying on Them
Jana Mueller
Jana Mueller

Corvids, the family of birds that includes crows and ravens, are canny beasts. They've been known to exercise self-control, count, hold grudges, and more. Now, new research suggests they possess at least a rudimentary Theory of Mind—the ability to attribute mental states to others.

A study in Nature finds that ravens can tell when someone else can see them, guarding their food when a peephole to their cache is open. While previous research suggested that birds might have an awareness of other animals' mental states, the results have been inconclusive. The Nature study is evidence that corvids can do more than just track other birds' gaze; they may understand the concept of "seeing."

Vienna-based researchers set up two rooms separated by windows that could be closed with covers. These covers had peepholes in them that could also be opened or closed. First, the 10 ravens were each allowed to cache food, while other birds were in the next room and the windows were open or closed. Then, they were trained to look through the peepholes to find food in the other room, so that they knew that the holes could be used to see through the window covers. Afterwards, each of the ravens was again presented with food with one of the two peepholes open. The adjacent observation room didn't have any birds in it, but the researchers played the sounds of another raven recorded during one of the previous trials.

When the birds heard the sounds of another raven in the next room, and the peephole was open, the birds behaved as if they knew they were being watched—they hid their cache of food quickly and didn't add more food to it as often, as if they knew that it might be compromised. However, they behaved normally when the peephole was closed.

This suggests that ravens don't just track their competitors' gaze to know when they’re being watched, but can infer from past experience when they can be seen.

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