Nature up close: The intelligence of ravens

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Ravens are always watching for a chance to steal any food they can.

By "Sunday Morning" contributing videographer Judy Lehmberg. 

Years ago a friend of mine and I drove from Huntsville, Texas to Alaska, a 10,000-mile round trip, in a red 1969 VW hippie van that had to be push-started due to electrical problems we didn't have enough money to fix. We were young and stupid, and it was one of the best trips of my life. We slept on hills, when we could find them, to make the next morning's push-start easier. Each morning my friend pushed the van from the back and I pushed from the driver's door, so I could jump in and pop the clutch. We got very good at that by the end of the trip.

Once we made it to Alaska, my now-husband flew there to join us. One evening we parked next to the Kenia River where several fly fishers were fishing for salmon as we started making hamburgers for dinner. One of the fishers (my now-husband) finally caught one and yelled his success back to us. We watched while he fought and landed a beautiful silver salmon. Then we turned back to begin cooking, only to discover a raven had eaten the entire pound of raw hamburger! We never even saw that greedy *&%$ raven until it swallowed the last morsel of meat. It had waited until we weren't looking and then stole our food, and I guarantee they know when you are looking at them.

Years later my husband and I stopped at a Yellowstone National Park picnic area to cook dinner. Yellowstone picnic areas are quite busy around noon, and the local beggar gray jays, chipmunks and ravens know it. But they are mostly deserted in the evenings. There was only one other group there, a family. I watched as the mom, illegally, threw a piece of what looked like chicken to a nearby raven. That raven must have had a really good lunch, because it didn't eat it. Instead it went to a bison patty, put the chicken on the ground and then pulled the bison patty over the chicken, hiding the meal from would-be thieves with a very non-chicken odor.

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Ravens argue over scraps at a grizzly bear's bison carcass.

Ravens, like us, are omnivores. Unlike us, they regurgitate what they can't digest, a great adaptation in birds that reduces their weight while flying.

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A raven examining the bed of our truck for food. It didn't get any.

Several studies show just how smart ravens are. One involved a wooden bar supported ten feet above the ground with several strings tied to the bar and pieces of meat at the end of each string. The ravens couldn't get to the meat from the ground or from the bar. Several ravens studied the situation and came up with a solution: While perched on the bar, they used one foot to pull the string up and the other foot to hold up the gathered string. After repeating that process several times they got the meat.

Another study looked at ravens' capabilities to remember individual humans. Several birds were shown an experimenter-trainer who gave them a piece of bread. Over time the trainer taught the ravens that if they gave the bread back they would get a more desirable piece of cheese. This trainer was the "fair" experimenter, always giving the ravens a piece of cheese in exchange for the bread. Then an "unfair" trainer was introduced, who would give the ravens bread and, when the ravens gave the bread back, would eat the cheese instead.

Two days later the experiment was repeated, this time with a fair, an unfair, and a neutral trainer whom the birds had never seen before. Six of the seven birds tested went to the fair trainer, while the seventh went to the neutral trainer. A month later the ravens were tested again, and the six ravens still remembered who the fair trainer was.

Judy Lehmberg is a former college biology teacher who now shoots nature videos.    

       
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