They’ll Take Two in the Bush – Crows and Ravens Show Patience

We live in an “act now!” world that frequently tests us, luring us with temptations and encouraging us to indulge. We may clearly see the importance of living within our budget yet still be dazzled by the shiny appeal of that new sports car; we may strongly believe in the benefits of a healthy diet yet still be weakened with lust for that large slab of double chocolate cake.

Nevertheless, we do sometimes succeed in delaying immediate gratification for the sake of something better in the future, in remembering those clichés about “good things come to those who wait” that our parents and grandparents inflicted on us. Undoubtedly, this is something we’re able to achieve because we’re humans, because we can be goal-directed and can prevail over our impulses, because we are more than unthinking animals who are captives to their immediate needs. Right?

Not so fast.

It is true that many animals seem unable to defer gratification, with prior experiments showing that animals such as rats, pigeons and chickens will rarely choose a delayed food reward over an immediate one, even if the delayed reward is much more attractive and the delay is only a few seconds. (From an evolutionary standpoint, this sort of impatience may make a lot of sense when an animal faces competition and future opportunities for food are unknown. “Life is uncertain, have dessert first!”)

To date, the major exception has appeared to be in primates: chimpanzees, bonobos, rhesus macaques and capuchin monkeys have demonstrated that they can wait for up to five minutes or so if that enables them to obtain a desirable food reward – a level of performance comparable to that of humans. (Interestingly, tests have shown that we humans seem to be much better at deferring money rewards than food rewards. Perhaps this, too, has a basis in natural selection, as food has been obviously always been an imperative, whereas money has existed for only an evolutionary blink of the eye.)

Also, while all of this might lead one to conclude that the ability to delay gratification lies solely within the province of humans and our closest relatives, it now turns out that corvids, the famously smart bird family (see prior AnimalWise posts here and here and here and here) that includes ravens and crows, may be every bit as patient.

When's dinner going to be ready? (from Wikipedia, photo credit: Cj005257)

As described in a paper published last week in Biology Letters, a team led by Valérie Dufour of the University of Strasbourg recently found that crows (Corvus corone) and ravens (Corvus corax) are able to tolerate delays of over five minutes in order to obtain a better reward, and that they may use the same sort of tactics to distract themselves while they wait as humans do.

In this study, six crows and six ravens were first trained to exchange tokens for food rewards, and then were given a series of “delayed exchange” tests. In each test, a bird would be handed an initial piece of food, which it could either eat immediately or, upon receipt of a signal after a designated waiting period, exchange for a more a desirable reward that it could see throughout the testing period. If the bird ate the initial reward or tried to exchange it too early, the test would end, but if it waited until the proper signal after the waiting period had elapsed – success, a better reward!

The researchers ran the tests with different types of reward (which they labeled as low-, medium- and high-quality) and with varying waiting periods (from 2 to 640 seconds).

Not surprisingly, the birds were generally more willing to exchange for the most highly preferred rewards and, as the following graphic illustrates, had a harder time as the delay period increased (with both crows and ravens maxing out at 320 seconds, or slightly over five minutes):

Interestingly, when the birds had to wait 20 seconds or longer before being able to exchange, they usually placed the “reward in the hand” on the ground and/or cached it in nearby crevices. The researchers believed this to be a distractive strategy, as “[t]hese behaviours probably alleviate the cost of waiting: not having to hold the food distracts the bird’s attention from it.”

As someone who routinely has to put snack food out of reach or even out of sight in order to prevent Homer Simpson-like devouring, this explanation makes a lot of sense to me. (For those of you who would prefer a more uplifting example of a strategy for avoiding temptation, I invite you to think about Ulysses having himself lashed to his ship’s mast so that he can safely listen to the songs of the Sirens.)

In any event, delaying gratification is significant because it involves, on some level, making a judgment about the future and the likelihood of achieving a prospective reward. While it’s not clear whether this entails a full “sense of self,” it is worth (re)noting that corvids are one of the few animals that have demonstrated the ability to recognize themselves in mirrors, a cognitive test that’s often used to measure whether an animal has at least rudimentary self-awareness.

Once again, corvids are no bird brains!

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ResearchBlogging.orgDufour V, Wascher CA, Braun A, Miller R, & Bugnyar T (2011). Corvids can decide if a future exchange is worth waiting for. Biology letters PMID: 21920957.

Rosati, A., Stevens, J., Hare, B., & Hauser, M. (2007). The Evolutionary Origins of Human Patience: Temporal Preferences in Chimpanzees, Bonobos, and Human Adults Current Biology, 17 (19), 1663-1668 DOI: 10.1016/j.cub.2007.08.033.

Heilbronner, S., & Platt, M. (2007). Animal Cognition: Time Flies When Chimps Are Having Fun Current Biology, 17 (23) DOI: 10.1016/j.cub.2007.10.012.

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Reconciling and Reassuring Ravens

Welcome to the elaborate, conflict-laden world of raven (Corvus corax) social dynamics!

Expanding on prior research demonstrating that ravens sometimes console fellow ravens who’ve been victims of aggression, researchers have now found that ravens who’ve been in conflicts often reconcile with their former opponents, the first time this behavior has been seen in birds.

Reconciling Ravens

In a study published this year in PloS ONE1, University of Vienna biologists Orlaith Fraser and Thomas Bugnyar found that reconciliation behavior does indeed occur between ravens who’ve had conflicts, particularly when the participants share a valuable relationship. While this sort of post-conflict kiss-and-make-up behavior is believed to play an important role in reducing stress and repairing relationships in primates and certain other mammals, it hadn’t been found in prior studies of birds, leading researchers to hypothesize that perhaps birds use different strategies to maintain social harmony or that reconciliation isn’t so important for birds, as their most important relationships are their pair bonds with mates, where they may be able to avoid significant conflicts in the first place.

Will we fight again? Nevermore! (photo credit: Audubon Guides)

Fraser and Bugnyar studied seven captive sub-adult ravens (who were too young to have formed pair bonds) for 13 months, measuring their behavior after a total of 197 aggressive conflicts (defined as incidents involving hitting, chasing or forced retreat). They then documented “affiliative behavior” (friendly interactions involving contact sitting, preening, beak-to-beak or beak-to-body touching) after each conflict, and compared it to the behavior occurring during neutral periods when no aggression had taken place.

They found that reconciliation (friendly contact occurring within 10 minutes of the end of the conflict) occurred after 37 of 197 conflicts and, in a significant majority of the cases, friendly interactions took place more quickly after a conflict than during the matched control period. Moreover, birds who were related or in “high value relationships” (pairs who had previously been observed to preen or sit in contact with one another) were more likely to reconcile. Interestingly, neither the sex-combination of the opponents nor the intensity of the conflict (measured by whether the birds hit each other and how many times a bird was chased or forced to retreat) impacted the likelihood of reconciliation.

The researchers did note that the behavior of ravens in the wild might differ from those in captivity, and that additional study would be needed to determine whether other factors, such as a history of food sharing, might also impact reconciliation behavior.

This study is significant in that it suggests that, through a convergent process and despite very different evolutionary histories, ravens have developed conflict resolution strategies that are similar to those employed by primates, reconciling with each other to preserve valuable relationships and reduce the chance of further discord.

Reassuring Ravens

This 2011 reconciliation research follows closely on the heels of a comparably-structured study2 that Fraser and Bugnyar published in 2010, also in PLoS ONE, establishing that ravens may possess a sense of empathy (yet another trait once thought to belong to humans alone, at least before evidence of empathy began turning up in primates and other animals).

In the 2010 study, Fraser and Bugnyar attempted to measure whether “bystander” ravens (those who’d witnessed but not been involved in an aggressive conflict) would console the conflict victim through “affiliations” (the same sort of friendly behavior – contact sitting, preening, beak-to-beak or beak-to-body touching – as was measured in the more recent “reconciliation” study).

Don't worry, you're much better looking than he is... (photo credit: pdphoto.org)

This time, they studied 11 sub-adult and two adult ravens raised in captivity, reviewing behavior after a total of 152 conflicts and in matching control periods and finding that both spontaneous and solicited (that is, initiated by the victim) bystander affiliations were likely to occur after conflicts.

More specifically, they found that unsolicited bystander affiliations were more likely to occur after more intense conflicts as well as when the ravens were related or shared valuable relationships, factors which suggested to the researchers that the affiliations served a distress-alleviating, or consoling, function. Also, the bystanders generally had stronger ties to the victims than to the aggressors, leading the researchers to conclude that it was unlikely that the bystanders were either acting as proxies for the aggressor to try to repair relationship between the combatants or trying to protect themselves from redirected attacks from the victims.

Based on these findings, Fraser and Bugnyar concluded that the best explanation for the bystanders’ unsolicited friendly behavior was that they were acting to console and alleviate the distress of the victims. The summarized the significance of this as follows:

Consolation is a particularly interesting interaction because it implies a cognitively demanding degree of empathy, known in humans as ‘sympathetic concern’. In order for a bystander to console a victim, they must first recognize that the victim is distressed and then act appropriately to alleviate that distress, requiring a sensitivity to the emotional needs of others previously attributed only to humans.

While the researchers noted some caveats, including the fact that study didn’t attempt to record vocalizations and that research on ravens in the wild was still necessary, they concluded that “the findings of this study … suggest that ravens may be responsive to the emotional needs of others.”

So, before you leave, here’s a multiple choice test regarding the moral of this story:

  1. Ravens are super smart, just like crows, nutcrackers, magpies and other corvids.
  2. We keep finding more and more ways in which other animals are able to do “uniquely human” things.
  3. If you plan on having an argument with a raven, you should make sure you bring all your raven buddies with you for support.
  4. All of the above.

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1Fraser, O., & Bugnyar, T. (2011). Ravens Reconcile after Aggressive Conflicts with Valuable Partners PLoS ONE, 6 (3) DOI: 10.1371/journal.pone.0018118.

2Fraser, O., & Bugnyar, T. (2010). Do Ravens Show Consolation? Responses to Distressed Others PLoS ONE, 5 (5) DOI: 10.1371/journal.pone.0010605.

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