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Can Fish Taste?

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iStock

You probably know what fish tastes like, but do you know how fish taste? Like all vertebrates, fish have five senses, including a sense of taste. And it’s probably more powerful than yours.

For fish, taste isn’t limited to the tongue. Fish have taste buds not just on their tongues, but on their lips and bodies, too. Taste buds need moisture to work (try eating with a dry mouth), and because fish are surrounded by water all the time, taste buds can survive on the exterior skin of their flanks and fins as well as inside their mouths.

Being able to taste with their bodies helps fish find food. Instead of smelling dinner nearby, they can taste it, long before the meal gets anywhere near their mouth. Bottom-feeders like catfish are especially keen tasters, which helps them locate edible morsels in muddy, dark waters. The channel catfish has around 680,000 taste buds [PDF] all over its body, including on its whisker-like barbels. That’s an especially high number of taste buds compared to most other animals (humans have about 5,000 in their mouths).

Having taste buds outside the body may help fish know what to eat when they can’t smell (fish have nostrils and pick up chemical cues similar to the way we would smell—minus the air, of course). A study of another scavenger called the deep-sea grenadier concluded that the fish’s sniffer became ineffective at close ranges, leading the fish to poke around with their barbels instead.

It’s kind of like having taste buds at the end of your fingertips.

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Crafty Crows Can Build Tools From Memory
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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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