22November2019

Andaman Chronicle

The Daily Diary of the Islands

What could that crow have been saying to me?

Maneka Sanjay Gandhi

A few days ago I was on my early morning walk when a crow sitting on my gate started cawing to me. He was very agitated and I stood there trying to understand what he wanted. After two minutes I turned my back and started walking off. Immediately he flew at my head and pulled my hair. I turned around mystified and, because I didn’t know what else to do, I brought him a biscuit and water. He took a piece, honed it against the gate till it became a swallowable size, gave me one last disgusted look and flew off.

Crows and ants are my “thing”. So smart, so elegant, so sophisticated, so family minded, so disciplined, everything that humans should be and are not.  Every few months I write about them, and each time it is about a new facet of their intelligence which so outshines mine.

What is intelligence? Flying to a country several oceans away and landing in the same tree. Is that not uncommon intelligence? But we only measure intelligence by comparing it to things we do, like mimicking human speech, or adding two and two.

According to a study, published in the journal Behavioral Ecology and Sociobiology, crows have a sharp memory for human faces and can even remember which person is dangerous. Even if they meet the same person in a new place, they will recognize them. In an experiment, researchers in masks held the bodies of dead crows while laying out food for live ones. The crows rejected the food, alerted all the other crows and attacked the researchers. When the researchers returned weeks later wearing the same masks and without the dead crows, the birds continued to harass them. No food was picked up in the area for days after. When a crow encounters a mean human, it will teach other crows how to identify the human. Crows recognize cars, gaits and even timings, and they hold grudges.

Researchers captured 12 crows while wearing one face mask, and then housed them and fed them wearing another. After four weeks in captivity, the authors imaged the crow's brains and they found that, like humans, the birds have the ability to recognize people tied to their experiences. When shown the face of their captors, the threatening face "activated circuitry known in humans and other vertebrates to be related to emotion, motivation, and conditioned fear learning". In contrast, when they saw the caretaker face, it activated areas of the brain tied to associative learning, motivation, and hunger. In other words, much like humans, the crows recognize faces, and link them to emotions and memory.

How smart are they?  In 2018 a study done by Von Bayern, Danel, Auersperg, Mioduszewska and Kacelnik, Compound tool construction by New Caledonian crows, published by Nature Scientific Reports, used eight wild New Caledonian crows. In phase I, the birds were provided a long stick and a baited test box where food was within reach when using the stick, but not without it.  In phase II instead of a single long stick, they were given a hollow cylinder and a second, thinner cylinder that needed to be combined in order to generate a tool long enough to reach the food.  In phase III, the birds were given new combinable items. In the final phase, birds were presented a bait box that required the combination of more than two elements.

The birds passed the initial tool test, then combined the two elements to get the food and then used this knowledge to combine the new objects. In the final phase, one bird succeeded in making a tool that required more than two elements. These findings showed that New Caledonian crows are smarter than chimpanzees and gorillas in making compound tools. New research shows that New Caledonian crows carve thin strips of wood into skewers, and bend wires into hooks, and keep their favorite stick tools cached in “toolboxes” for further use!

In another study of Caledonian crows, the researchers set up a “vending machine” that could be operated by putting a piece of paper of a certain size into a slot, which would then release a treat. The crows quickly learned how to put the paper into the vending machine to get food. Then the crows were given paper of the wrong size for the vending machine. They had no reference of how big to make the paper, except from their memory. The crows made the paper into the right size and shape without any problem.

Aesop’s famous fable “The Crow and the Pitcher” tells of a thirsty crow who drops pebbles into a pitcher with water near the bottom, raising the water level high enough to let the bird drink. Scientists, trying to corroborate this story, found that crows given a similar problem dropped stones into a tube containing water, but not into a tube containing sand. They dropped dense objects into the water until the water came within reach. They did not select objects that would float in the water, nor did they select ones that were too large for the container. Human children gain this understanding, of volume displacement, around the ages of five to seven. Crows do indeed understand basic cause-effect relations.

A recent research collaboration, between Moscow State University and the University of Iowa, has discovered that crows are able to solve problems that require abstract thinking. For example, sameness and differentness are key abstract ideas, because two or more items of any kind—coins, cups, caps, or cars—can be the same as or different from one another. Analogical reasoning is considered to be the pinnacle of cognition and it only develops in humans between the ages of three and four.  The team trained crows to match items that were the same as each other (same colour, same shape, or same number). Next, the birds were tested to see if they could match objects that had the same relationship to each other. For example, a circle and a square would be analogous to red and green rather than to two oranges. The crows grasped the concept the first time, without any training in the concepts of "same and different."

Crows have relatively large brains for their body size, compared to other animals. Their brains have a higher neuronal density – the number of neurons per gram of brain than primates. So, they pack more processing power into their small brains.

I am still puzzled. What could that crow have been saying to me? 

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