Wednesday, September 12, 2012

What Do Animals Think of Their Dead?

You’re running around, going about your day, and suddenly you see a dead guy lying in the sidewalk. What do you feel? Sad? Scared? Do you look around to see if you might be in danger too? Would you feel any differently if the dead body on the sidewalk were that of a squirrel, and not a human? Do animals share these same emotional and thought processes when they come across their own dead?

Teresa Iglesias, Richard McElreath and Gail Patricelli at the University of California at Davis pondered this philosophical question themselves. Then they set off to scientifically test it.

A western scrub-jay collecting peanuts from a windowsill.
Photo by Ingrid Taylar at Wikimedia.
Teresa, Richard and Gail had noticed that when a live western scrub-jay encounters a dead western scrub-jay, it hops from perch to perch while calling loudly, a response the researchers called a “cacophonous reaction”. This boisterous response usually attracts other scrub-jays, which either join in with their own cacophonous reaction or just sit quietly observing. Is this truly a response to seeing their own dead?

The researchers put bird feeders baited with peanuts in backyards all over Davis, California (with the permission of the backyard-owners, of course). Once they find a feeder, western scrub-jays take the peanuts one at a time and fly off to cache them away before returning for another peanut. While the scrub-jays were away caching a peanut, the researchers put a collection of painted wood pieces on the ground, arranged to vaguely look like a dead scrub-jay. Then they snuck away to watch if the scrub-jays responded when they returned. Several days later, they came back to the same feeders, waited until the scrub-jay was away caching a peanut, and then placed an actual scrub-jay carcass and feathers (usually found somewhere in the area). Then they snuck away again to watch if the scrub-jays responded any differently when they returned.

video
Watch the behavior of western scrub-jays before and after
the placement of a dead scrub-jay. The “after” response starts
about one minute into the video. Video by Teresa Iglesias.

And in a nutshell, they did. When the scrub-jays returned to find a dead scrub-jay, they called like crazy and hopped around in a full-blown cacophonous reaction. In most cases, this reaction attracted other scrub-jays who joined in the lively response. Additionally, when the dead scrub-jay was present, they took 90% fewer peanuts. None of this ever happened in response to a pile of painted wood. When a scrub-jay returned to find painted wood, it went about its day, calling at normal rates and collecting peanuts as usual. One jay was so unconcerned by the painted wood, it even cached peanuts under it!

video
A western scrub-jay thinks the painted wood makes
a good peanut-hideaway. Video by Teresa Iglesias.

This convinced the researchers that the scrub-jays were not simply responding to something new near the feeder, but were instead responding to dead bodies. But does it matter whether the body is a conspecific (the same species) or a heterospecific (different species)? And what do these group responses mean? Are they gathering in mourning? Or is their response a way of hollering, “Look out! Something out there is killing us!”?

To find out, the researchers did the same thing they had done before, but this time, they placed either a scrub-jay carcass or a mounted great horned owl (a scrub-jay predator). Interestingly, the scrub-jays responded with the same cacophonous reactions and avoided the peanuts in both cases. However, the scrub-jays called for longer and defensively swooped at the mounted owl, something they didn’t do to the scrub-jay carcass. To check if this heightened response to the owl mount was due to its lifelike position, they repeated the study, comparing scrub-jay responses to a scrub-jay carcass or a mounted scrub-jay. Although the dead-looking carcass always elicited cacophonous aggregations, mounted scrub-jays only elicited cacophonous aggregations a third of the time. But when jays did respond to the scrub-jay mounts, they often swooped at it as if it were a competitor, something they never did to a scrub-jay carcass.


What does this all mean? Western scrub-jays respond to conspecific (scrub-jay) carcasses not just because their appearance is surprising, but because they may represent some kind of risk. They seem to recognize that the carcass is not a living threat, because they don’t swoop at it like they do to both owl and scrub-jay mounts. But they do produce an alarm response, much as they do when a predator is present. So their responses to dead scrub-jays are not so much “funerals” in the way that people mourn and reflect on their dead, but rather a way to announce a risk of getting hurt or killed.

Are western scrub-jays uniquely aware of the risk a dead conspecific may represent? Maybe not. Although this was the first comprehensive study of this phenomenon, similar behavioral responses to dead conspecifics have been observed in ravens, crows and magpies, all members of the corvid family of birds, like scrub-jays. But rats and even bees have also been observed to avoid dead conspecifics. Many animals may be more cognizant of death than we give them credit for.

Want to know more? Check this out:

Iglesias, T.L., McElreath, R., & Patricelli, G.L. (2012). Western scrub-jay funerals: cacophonous aggregations in response to dead conspecifics Animal Behaviour DOI: 10.1016/j.anbehav.2012.08.007

8 comments:

  1. "baited with peanuts", not "bated with peanuts"

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  2. I find the last sentence to be very true, especially given some of the research on the behavior of elephants and other animals surrounding the death of their own babies. The more research I read regarding animal behavior, the more my personal belief of the intelligence of animals seems supported. So glad that research such as this continues, it is very important!

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  3. This research echoes what we who work with animals full-time have long known...there is a decidedly marked reaction of one species to the death of one of its own. Publicizing this research might go a long way to increasing the visibility of such impact in cases of animal abuse resulting in death.

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  4. I'm curious about the Scrub Jay carcasses "usually found somewhere in the area." I've lived in areas with a lot of Scrub Jays, and I've rarely seen a carcass. Were the dead jays found by others and turned over to the researchers as specimens?

    I also agree with Christian. Although I know scientific substantiation is important for culture at large to better understand and embrace these facets of animal behavior, it saddens me that the language of proof can never fully establish an accurate level of consciousness in other animals. Absent common language, I fear that non-human animals will never get their fair shake in terms of our impressions of their sentience and intelligence.

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    Replies
    1. It's amazing how much more you can find when your project depends on it :) ...and yes, community members helped with the specimen collection.

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  5. Seems to me that a dead predator wasn't the right substitution. It would naturally elicit a threat response if it was alive, so it's not investigating the scrub-jays reaction to death. More interesting to know what the reaction would be to 1) a different species that competes for resources, 2) a different species that doesn't compete but is a similar form (a same-sized bird) 3) a different species that has an unrelated form (a small mammal).

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  6. Thank you so much for sharing this post!
    The behavior does vary!

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