A Bit Different Physiology

Tonic Immobility (‘Hypnosis’) In Chickens

Most of us are probably familiar with hypnotist shows in which volunteers are recruited to participate in a series of activities that entertain the audience, by inducing them to behave in embarrassing ways, including acting like a chicken.

I’m not sure how credible those performances are, but I do believe that hypnosis can be a legitimate practice. It’s defined as “a human condition involving focused attention, reduced peripheral awareness, and an enhanced capacity to respond to suggestion”.

Fewer of you might be aware of ‘chicken hypnosis’. No, it’s not accomplished by slowly swinging a watch back and forth in front of a chicken, while softly whispering “you are getting sleepy, very, very sleepy” until the bird is putty in your hand.

It can be achieved in a couple of different ways: either turning a bird on its back and gently restraining them or drawing a line directly in front of them and pushing their beak to the ground. Both techniques result in a chicken that appears totally malleable. A little scratching beneath the surface of these party tricks meant to amuse the guests reveals that those birds are actually experiencing tonic immobility (TI).

When an animal encounters a threat, their body responds quickly and unconsciously to protect them from danger. They will first freeze, even if only for a split second, to rapidly assess the situation. Usually the next option of either fight or flight follows, but there is a third possibility.

We might know the expression ‘playing possum’ in which those marsupials act as though they were dead. That behaviour, also known as thanatosis, is an anti-predation behavior used by a number of animals, including opossums, spiders, snakes and yes, chickens.

Thanatosis is a form of tonic immobility: a state of profound but reversible, involuntary paralysis, which is induced by physical restraint. The animal may appear catatonic, while remaining conscious and calm anywhere from 30 seconds up to half an hour. It’s thought to be the final option in a series of anti-predator strategies when an animal is faced with danger and other forms of defense aren’t possible. Scientists theorize that the body enters TI when running or resistance would increase the risk of pain or suffering.

People in Facebook chicken groups often wonder why their birds run from them and struggle at being handled. The simple reason is we appear as large predators and they are prey animals. Tonic immobility is a fear-based response to being restrained. In other words, the chicken is convinced that it’s going to die and freezes. Farmers’ knowledge of this adaptation was first recorded in 1646.

A number of studies on tonic immobility in chickens have been conducted and found that birds restrained for 15 seconds demonstrated the following:

  • Increased heart rate, respiration and temperature.
  • TI was longer in birds housed in a) cages rather than in pens, b) large rather than small flocks, or c) birds removed from their flock.
  • TI was shorter in chicks raised in a flock; and in adult birds, if a flock mate accompanied them.
  • Dominant hens remained immobilized longer than those lower in the pecking order.
  • The immobility reaction is connected to genetics, and high or low responsiveness to new experiences in chicks.
  • TI is used as a behavioural tool for assessing a bird’s reactivity and/or fearfulness and may provide insight on issues of humane chicken management and housing systems.

If you’ve ever ‘hypnotized’ a chicken I’d hope that you wouldn’t repeat it now that you know what’s actually going on. Although it looks harmless, and even humorous, birds are responding out of fear. You might find turning a bird on it’s back makes them easier to handle, but it’s not healthy for them. Always hold and carry birds in an upright position.

I often see folks recommend dealing with flighty birds or aggressive roosters by turning them upside down because they ‘calm’ down. Again, that bird appears to be complying, but only because it has no other options. They are essentially experiencing physiological distress. When held upside down, gravity causes their organs to squeeze against their lungs and air sacs, making it more difficult for them to breathe.

When you know better you do better.

Credits: NCBI: Science Direct; Smithsonian Magazine; World’s Poultry Science Journal

1 comment on “Tonic Immobility (‘Hypnosis’) In Chickens

  1. I learn so much from this site!

    Liked by 1 person

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