Talk:Constriction

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With all due respect to previous contributors; as an experienced keeper and breeder of (Australian) pythons for over forty years, I strongly disagree with the content of this article, but unfortunately have no citable material immediately at hand refuting the claims I take aversion to. Unless there is an unusually large discrepancy between the size of the snake and its prey, the mechanism causing death is solely asphyxiation caused by denying the prey any opportunity to breathe. While it is true that the prey will suffer some decrease in circulation, this effect is confined to the tissues nearest the skin (unless the snake, and only then in very rare instances, is wrapped around an animals neck!). The major blood vessels within the thorax are relatively far too large to suffer the decrease in blood flow necessary to cause cardiac arrest - to achieve this, the ribcage would need to be entirely crushed or flattened, and this does NOT happen. Please see also the python entry for a better description of constriction. Unless some credible references are provided in support of the cardiac arrest hypothesis, I shall consider replacing this with an entirely rewritten article when I next visit this page. Peter b 01:45, 27 March 2007 (UTC)

I'm re-writing the article, but FYI - the 'traditional' hypothesis is that snakes kill by suffocation, but the death of some prey items seems too fast for that, prompting the suggestion that the pressure of constriction causes cardiac arrest (Hardy, 1994. A re-evaluation of suffocation as the cause of death during constriction by snakes, Herpetological reviews). The proposed mechanism is that the pressure of constriction would lead to increased pressue in the main body cavity, in which the descending aorta and inferior vena cava are directly exposed. This would in turn transmit the pressure change directly to the heart, and if the prssure is greater than the max systolic pressure, the heart would stop (Note that blood flow does not need to reverse, but only for pressure in the body cavity to exceed what the heart can generate). [b]However[/b], this has not yet been verified. Brad Moon has made some compelling pressure measurements indicating that snakes can produce the pressures needed (Moon, 2000. The mechanics and muscular control of constriction in gopher snakes (Pituophis melanoleucus) and a king snake(Lampropeltis getula), Journal of Zoology), but hasn't proven that this is the cause of death.

In short, the cardiac arrest hypothesis should be seen as just that, a hypothesis currently being tested, but one with some interesting data so far. Mokele August 30, 2007 —Preceding unsigned comment added by Mokele (talk • contribs) 20:55, August 30, 2007 (UTC)

I often saw the eyes bulging out of mice during constriction (along with their purple tongue bulging out of their mouths, when I was younger and fed live rodents to the pythons and boas that I kept), and while the pressure might not be high enough to crush the victim, there certainly is enough pressure to cause problems in addition to asphyxiation such as interference with proper blood circulation, which I think could potentially cause, among other things, the victim to black out sooner than would happen from the suffocation alone. Constriction can be described as suffocation, rather than crushing, but really it is more like suffocation plus. A chicken who gets constricted by an anaconda has more energy being put toward its demise than does a chicken who is merely being smothered by a pillow, so I can see the first one dying quicker. Neptunerover (talk) 07:56, 4 November 2009 (UTC)

it's not only snake-related! see Asphyxia -- Melaen 13:07, 30 November 2005 (UTC)

Article says the sanke bites and holds on before applying constriction. Is this correct? RJFJR 01:27, 9 December 2005 (UTC)

The article says that snakes don't crush bones, but asphyxiate their prey, and then in the next sentence says they don't asphyxiate their prey, but make their hearts stop beating. Which is true? Also, the only informative section is on snake constriction, which is rather short - it could be moved into the boa page, and then this page could turn into strictly a disambiguation page like it looks like it wants to be? Kjl 15:43, 11 April 2006 (UTC)

"Boa" is kind of imprecise, but even in its broadest sense (members of the family Boidae), it doesn't encompass all snakes who use constriction. Many non-boids employ constriction, sometimes in combination with venom.

Constricting snakes squeeze tighter every time the prey takes a breath. The prey's lungs are thereby deflated, and the heart is compressed. Remarkably, there is still a lot of confusion and uncertainty as to the actual cause of death (as we've seen right here on this talk page). My guess is that both factors — interference with breathing and with circulation — contribute to constrictors' ability to make such quick kills (as has been noted, constriction kills more rapidly than one would expect if asphyxiation were the only weapon in their arsenal), preventing an adequate supply of oxygen from getting to the tissues (in particular, to such noteworthy locations as the brain).

Although, to the best of my knowledge, this hasn't been studied in other species, boa constrictors have been found to use the presence or absence of a heartbeat to decide when it's safe to stop constricting (see, e.g., http://rsbl.royalsocietypublishing.org/content/8/3/473) — as soon as the snake can no longer detect a heartbeat, he or she will keep squeezing for a bit longer (you know, just to be sure), then relax and start preparing to swallow. This is a tricky process. In spite of their inability to break their food into more manageable-sized pieces by biting, tearing, chewing, etc., as other vertebrates do, Macrostomate snakes frequently eat prey that is larger than their own heads; some species have even been known to gobble down a meal bigger than their whole body. Such large prey can pose a major threat to the predator, so snakes had to evolve a technique for taking down their prey that would not give it am opportunity to fight back. Constriction qualifies: once the snake is coiled around the prey, it's pretty much trapped in the snake's coils and no longer a threat.

Snakes are the ultimate binge-eaters, a lifestyle which has its advantages...after such a large meal, they curl up to chill out and digest, and may not have to eat again for weeks. During that time they don't have to take the risks associated with hunting and eating. While constriction does immobilize the prey itself, there is always the risk that a predator might happen along (especially if the snake is in an exposed location), in which case the snake may have to abandon the prey in order to flee, which would suck. It's therefore important for the snake that it not take long for the prey to die. Snakes (even venomous ones) are even more vulnerable while swallowing, which can take a long time, especially with large prey. Sometimes, after making a kill in an open area, a snake will drag the prey somewhere more private, such as a burrow or a spot concealed by vegetation, before eating it. Mia229 (talk) 17:23, 25 August 2012 (UTC)

Suffication-Is it true??

Discovery Communications made a documentary called Anatomy Of A Snakebite. They did an experiment about constriction and said that instead of sufficating the victim, the snake sueezes you until all your blood is in your head and your eyes may even want to pop out.

how fast is constriction?

One bit of info that would be useful to include here: how long does it take for a constrictor (depending if it's a dedicated constrictor like a boa/python or uses a mix of techniques like certain colubrids) to kill prey of various sizes (relative to the snake)? And perhaps, a comparison for snakes that use venom only (like most viperids & elapids)? Just a thought. 174.111.242.35 (talk) 03:10, 1 July 2011 (UTC)

File:Diamond Python around ring tail possum.jpg Nominated for speedy Deletion

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Pressure

The article currently states that "it has been found that the green anaconda (Eunectes murinus) exerts a constriction pressure of 6 kg/cm², which effectively means a total strength of 4000 kg.[4]" The provided source, however, only provides one pressure value "4 PSI (pounds per square inch)". I am not familiar with "kg/cm²" as a unit of force, but perhaps "kilogram-force/square centimeter" is meant. In that case, onlineconversion.com calculates "6 kilogram-force/square centimeter = 85.340 pound/square inch", which is about 20 times the pressure given by the source. Also, how is the "total strength" calculated. Can anyone clear up this discrepancy? -AndrewDressel (talk) 15:38, 6 August 2013 (UTC)

External links modified

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Non-primary Source

Hello All, I noticed that citation number 5 is a BBC article that cites as a primary source of information the journal article cited here as reference number 7 (from the Journal of Experimental Biology). It seems that as an encyclopedia we should be citing primary sources whenever possible. It would be an easy change to make both citations the same and not reference the non-primary source at all. I haven't had any skin in the game on this entry so far so I will leave it to those more invested in it to decide if they want to make the change. Kirkmona (talk) 14:25, 17 October 2018 (UTC)

Per wp:psts

Wikipedia articles should be based on reliable, published secondary sources and, to a lesser extent, on tertiary sources and primary sources. Secondary or tertiary sources are needed to establish the topic's notability and to avoid novel interpretations of primary sources.

so the secondary source is desirable and you should probably not remove it. -AndrewDressel (talk) 15:00, 17 October 2018 (UTC)