We're sure you have your favourite animal. It may even be a really smart one. But corvids - such as crows, magpies and ravens - really are something special. In fact, they're some of the most intelligent animals in the world.
And here we've gathered some of the finest examples of just how clever these gorgeous creatures can be.
1. Crows can reason out cause and effect
In a test on New Caledonian crows, crows were placed in an enclosure wherein a stick would emerge from a hide. They used two scenarios: in the first, a human was observed entering the hide before the stick moved, and leaving after. In the second, the human remained hidden.
In the first, the crows were much more relaxed after the human left, correctly linking the movement of the stick to the presence of the human. They would forage for food, and behave normally. In the second, the crow had no other reference for the stick's presence, so they remained wary.
"These results really seem to be showing that crows react in a very similar way to humans in a situation that requires them to reason about a hidden causal agent," says biologist Alex Taylor.
2. Crows understand water displacement
In an experiment with tubes published in PLOS One, scientists determined that New Caledonian crows can not only tell the difference between water and sand - they also understand water displacement.
The test involved tubes containing water and a treat floating on top out of reach. The crows filled the tubes with enough rocks or other heavy items to bring the food within reach.
They also were presented with different scenarios, such as tubes with different water levels. The crows showed an absolute preference for the tube that would get them the food with the least amount of work.
Their success rate was on a par with seven-year-old children, the researchers said.
3. Crows hold a grudge - and pass that grudge on to other crows
Ever wonder why crow researchers sometimes wear masks? It's because crows can recognise human faces, especially the faces of humans who have done them wrong.
So, if you're trying to record how crows react to negative stimuli (such as being caught and tagged), you don't want to do that using your real face. If you do, you'll get loudly scolded by the agitated flock every time you approach, as biologist John Marzluff discovered and detailed in a 2011 paper.
Good thing he did, too. A few years later, he found out that crows not only hold onto that grudge - they tell other crows about it, too.
Within the first two weeks after trapping, around 26 percent of crows scolded the human wearing the danger mask. Around 15 months later, that figure was 30.4 percent.
Three years after the initial trapping event, with no action towards the crows since, the number of scolding crows had grown to 66 percent.
4. Crows hold funerals for their dead
When a crow dies, other crows are often observed gathering around and making a lot of loud noise - much like humans, really. The reason for this was unknown until 2015, when crow researcher Kaeli Swift crowdfunded research to try and figure out why.
Her conclusion, published in the journal Animal Behaviour, was that crows gather around their dead fellows to learn about danger.
And it works. The city of Chatham, Ontario is beneath a crow migration route, and they plague the town on their way through. Every attempt to get rid of them has failed - including shooting at them with pellet guns. The crows learnt how to fly just high enough to evade the fire.
5. Ravens are smart enough to be paranoid
A study released in early 2016 found that ravens possess something known as the Theory of Mind - that is, the ability to recognise mental states within themselves, and extrapolate that others have mental states, too, and that those mental states in others may differ from their own.
Ravens like to stash food for later, and had been observed doing so more cautiously when other ravens were around.
To test this idea, ravens were trained to use a peephole to watch a human hiding food in an adjoining room. Then they were put in the second room with the food, and observed in two conditions: with the peephole closed, and with the peephole open and a loudspeaker playing raven cries.
They behaved just as if another raven was in line-of-sight.
This indicated, the researchers wrote in their paper, "that they can generalise from their own experience using the peephole as a pilferer and predict that audible competitors could potentially see their caches. Consequently, we argue that they represent 'seeing' in a way that cannot be reduced to the tracking of gaze cues."
6. Crows can solve complex, multi-step puzzles
This crazy impressive experiment was conducted as part of a BBC Two program called Inside the Animal Mind, putting crows to the test with the most complex animal puzzle ever.
And not lab crows, either. The crows were captured from the wild one at a time, and kept for just three months.
This one, nicknamed 007, is apparently a genius. The puzzle involved eight individual steps that had to be solved in a very specific order to release the food reward. He had to collect the tools, then use them to complete the next step of the puzzle. He was familiar with the individual tools, but had not had to combine their use before.
Seriously, watch the video. It's so good.
7. Crows can fashion tools
OK, crows can use tools. Great!
But what do they do if there's nothing available? Turns out they just make their own, the resourceful little poppets. In 2015, researchers announced they had filmed the first ever video evidence of crows fashioning tools in the wild using a specially developed spy camera mounted on the crows' tail feathers.
They were observed snapping twigs from trees, then stripping it of bark and leaves, and fashioned the node into a hook. They then used these tools to probe into small spaces for food.
"The behaviour is easy to miss – the first time I watched the footage, I didn't see anything particularly interesting. Only when I went through it again frame-by-frame, I discovered this fascinating behaviour. Not once, but twice!" researcher Jolyon Troscianko said.
"In one scene, a crow drops its tool, and then recovers it from the ground shortly afterwards, suggesting they value their tools and don't simply discard them after a single use."
8. Ravens use social ostracism to punish selfish peers
When someone in your friend group acts like an idiot, they may find themselves suddenly disinvited from social events, unfriended from Facebook, and their messages unanswered. Ravens don't have Facebook, but they do exercise similar ostracism towards conspecific dickheads.
In a 2015 study, researchers from the University of Vienna gave ravens a task wherein they would only receive the reward if they cooperated, pulling on ropes to raise a platform which had two pieces of cheese, one for each raven.
If one raven stole their companion's cheese, as well as their own, they were on the outs: the other raven would refuse to cooperate with them - but they would cooperate with other ravens who played fair.
"Such a sophisticated way of keeping your partner in check has previously only been shown in humans and chimpanzees, and is a complete novelty among birds," lead researcher Jorg Massen said.
9. Crows can exercise self control
Crows aren't driven purely by instinct - they can experience anticipation, and exercise self-control if the end result is a greater reward.
A 2014 study devised a test based on the Stanford marshmallow experiment, a 1960s study into delayed gratification in children. The first step was to determine which snacks the crows liked the most. The researchers fed them grapes, bread, sausage, fried fat and other treats.
Next, they were given a snack and the option to trade their snack - if they were willing to wait. They could either receive a better quality snack - meat in exchange for a grape, for instance - or a higher quantity of the same snack.
The birds preferred to wait until a better snack was on offer, but if it was just more of the same, they weren't. In some cases, they waited up to 10 minutes for a better snack. The fact that they waited for better quality, not quantity, showed that they were waiting because they wanted to - not because they were actually hungry.
10. Ravens can plan for the future and barter for items they need
When trained in the use of tools, ravens recognise the items as valuable and can set them aside against a future need. To figure this out, researchers trained ravens to release a treat by sticking a tool into a tube sticking out of a box.
Then they took the tool and box away, returning an hour later to offer the raven a choice of objects - one of which was the tool. After another 15 minutes following the raven's selection, the box was returned - 80 percent of the time, the raven had chosen the correct tool. The experiment was repeated with a 17-hour interval in returning the box, in which case the ravens had a 90 percent success rate.
For the next part, ravens had been trained to return a token to a human in exchange for a food reward. After an hour, they were offered three trays in succession with a choice of objects, one of which was the token and another of which was a low-quality snack, for a total of three tokens.
They chose the token on average around 73 percent of the time. After 15 minutes, the bartering experimenter would come back, and the raven exchanged the tokens for the prize.
"This study suggests that ravens make decisions for futures outside their current sensory contexts, and that they are domain-general planners on par with apes," the paper concluded.
11. Ravens remember people who have been nice to them
You know how crows hold a grudge? Well, corvids also remember people who have been nice to them. There was, of course, that adorable case of a little girl who crows started bringing shiny objects to after she regularly fed them - but there's been a scientific study on the subject too.
Again, it involves ravens trading a low-quality snack (bread) for a high-quality snack (cheese), which they'd been trained to do. Then two humans brought the cheese to trade for the bread. One experimenter would fairly give the cheese when the crow handed over the bread. The other experimenter ate the cheese themselves after being given the bread.
Then, after an interval - two days, and then later one month - three humans entered the enclosure, the fair one, the unfair one, and a neutral control. The raven was given a piece of bread to trade. Most of the ravens chose to trade with the fair experimenter - indicating that they remembered being cheated out of delicious cheese and weren't falling for that again.
12. Ravens use gestures to communicate
Before babies learn to speak, they communicate using gestures. Pointing at objects they want, for example. Outside of primates, this means of communication had never been observed in another species - until researchers observed wild ravens doing it.
They use their beaks like hands, Simone Pika from the Max Planck Institute for Ornithology and Thomas Bugnyar from the University of Vienna found.
They recorded 38 interactions between pairs of ravens, 25 of which involved the raven picking up an object and showing it to their companion, and 10 of which involved ravens offering an object to their companion.
"These distinct gestures were predominantly aimed at partners of the opposite sex and resulted in frequent orientation of recipients to the object and the signallers. Subsequently, the ravens interacted with each other, for example, by example billing or joint manipulation of the object," the researchers said.
13. Crows like to play
We're just going to leave you with this, because it's just so gosh-danged delightful.
Now go follow the Tower of London's Raven Master on Twitter. And don't say we never give you anything.
A version of this article was first published in December 2017.
#Nature | https://sciencespies.com/nature/13-strange-reasons-why-crows-and-ravens-are-definitely-the-smartest-birds-hands-down/
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