Posted By crates on December 13, 2007

     The Hognose snake (Heterodon platyrhinos) was going through its impressive repertoire.  First it flattened its head and neck out like a cobra, showing the lighter yellow color between the dark scales.  Then it raised its head up off the ground, making striking motions (with its mouth closed).   However, it ignored my hand when I held it up before its head, continuing to hiss and flatten its neck as it attempted to crawl away.  This behavior is what has given this harmless snake (although some may have a reaction to its saliva) such names as Spreading Adder and Death Adder.   When I patted it with my hand the snake went into further histrionics, gaping its mouth wide, writhing as if in its death throes, salivating profusely, tongue hanging out of the gaping mouth, dirt clogging its mouth, until finally it stopped all motion lying on its back apparently dead.  Poor thing!  However, when I tried to turn it back over onto its stomach it would immediately turn back over on its back.  It lay there, muddy mouth wide open with its tongue lolling.  I reached down and tried to turn it over onto its stomach again, whereupon it turned back onto its back.  When I pushed my finger in its mouth, it totally ignored it.  This is one of my favorite snakes!

        This is the classic reaction of this snake to potential predators, and I had seen it and marveled over it many times.  I waited once again as I had many times in the past, to see what it would do.  I sat motionless a few feet away, until after a few minutes, I noticed the mouth of the snake close and its head turn.  It appeared to be looking around.  When I moved the snake went right back into its “death feigning” behavior.  If I stayed still, the snake would gradually recover, turn back onto its stomach and begin to crawl off.  It would revert back into its dead position if I made a movement towards it.

      In other words it seemed to have some sort of “conscious” control over its behavior.  The death feigning did not, in my opinion, represent an uncontrollable fit or a spontaneous, neurological reaction to hostile stimulai, but a voluntary response of some sort.  However, when I suggested this to another person, he pooh-poohed the idea saying that a primitive reptile like this Hognose snake could not possibly have a consciousness, thus there could be no voluntary action, but only an uncontrollable reaction to a stimulus.  I was nonplussed at this, but saw the reasoning.  He was saying that the brain was of insufficient complexity to show such a high order of reasoning…there could be no consciousness as I conceived of it.   I could understand his reasoning, but dang it, the snake acted as if it had some sort of voluntary control over its actions, immediately feigning death again if I made a movement during its recovery phase!  I couldn’t believe it was merely a stimulus/response reaction with no voluntary mediation.

     I hooked one of these snakes up to a Physiograph in the lab to record the breathing rate and electrocardiogram.  I thought that perhaps by comparing the readings for a snake not undergoing death feigning to those of a snake which was undergoing this behavior, some light could be shed upon the nature of this behavior.  I never obtained conclusive results.  It was suggested that I would have to open the snake up and correlate the readings with the actual observed heart beat…I was loathe to do this and dropped the whole thing.

       A few years later I held an opossum (Didelphis marsupialis) by the scruff of the neck watching its reactions to my rough handling…glazed eyes, open mouth, lolling tongue, limp body.  I placed it on the ground and it lay there motionless, apparently dead.  The Virginia Opossum (The “O” is not pronounced!) is famous for it’s death feigning behavior, and in some ways its act resembled that of the Hognose snake.  I drew back from the opossum and observed it. 

     Like the snake, the opossum slowly seemed to return to normal.  First its eyes lost its staring glaze and it began to look around.  Then its head moved slightly.  When I made a movement, it immediately lay still and its eyes regained their glazed look, staring into nothingness.  Like the snake, the opossum seemed to have a subtle voluntary control over the behavior.  If it was a convulsive fit, then it was a remarkably versatile type of involuntary neurological reaction, able to respond to the slightest stimulai.  Not only that but it appeared to be voluntary.  The nervous system of the opossum is a bit more complex than the snake, but its brain is still not as large as that of a similar sized dog or cat as shown when the two skulls are held side by side.  The cranium of the opossum is noticeably smaller.

    To test the opossum further I reached over and squeezed its nostrils closed.  The creature seemed unfazed, but it did begin to breath through its mouth which remained open.

     Anyway these behaviors and others got me to thinking about consciousness.  It seems to be assumed that creatures such as insects and other invetebrates have no consciousness, but are in essence little organic machines, and that in order for an organism to be conscious it has to have at least some sort of complex central nervous system.

     There are many definitions of consciousness with entire books being written on the question of what it is exactly.  One of the components of consciousness seems to involve behavior that is performed with an awareness of the action as opposed to actions that are performed without the awareness of the individual, being involuntary–no volition involved.

    This is an area that fascinates me, and as I research the subject further, I hope to write further on it.

Categories: nature
Tags: Consciousness, Death Feigning, Didelphis marsupialis, Heterodon platyrhinos, Hognose Snake, nature, Opossum