Learn about hens
All domesticated hens (gallus gallus domesticus) come from wild hens (gallus gallus) living in the forests of India and south-east Asia (Burma, Malaysia, Thailand and Cambodia). They were domesticated 8.000 years ago and were introduced to the Middle East and Egypt in the second millennium BC, Europe in the first millennium BC and America in the 16th century.
An adult hen weighs between 3 - 4 kg, as much as a cat. She has very developed hearing and vision and, due to the lateral location of her eyes, a very wide field of vision. Her eyes do not move, but their immobility is offset by long and continuous head movement.
She has no teeth, she swallows little pebbles, and the stomach muscles mash the solid food along with the stones to digest it.
In her natural environment, a hen lives for about ten years or more.
She eats what she finds on the ground: seeds, grass, leaves, little pebbles, worms or insects.
She sleeps upright, with her eyes closed and her head lying on her wings to avoid light.
She digs pits in the soil and rolls on the dust to clean and isolate her wings from the parasites.
Like humans, she discerns the red, green and blue colours, the violet light that is within the visible spectrum, and the ultraviolet that is invisible to the human eye. Because her eyes are so sensitive to infrared light, she can distinguish the sunrise up to an hour earlier than human beings. That's why roosters crow when we think it's still night time.
Intelligence and social life
"Hens undoubtedly have more abilities than we think, but it is psychologically beneficial to degrade the animals we use as food"
Dr. Siobhan Abeyesinghe, Royal Veterinary College (UK)
The intelligence of hens has been documented many times. They can solve complex problems, understand cause and effect, have memory and plan the future.
They are empathetic
Studies show that hens are intuited and sympathetic when their young or other hens are in distress or at risk, regardless of distance. (Edgar et al., 2011)
The hen is overprotective of her young ones. She begins to train them while they are still in the egg, communicating with them with cooing and whistling, and they respond with tweets.
Later, she teaches them what is safe to eat and what is not.
Chicks also learn from personal experiments. If they are given simple grains and grains of other colour with an anti-inflammatory substance, they perceive the effect of the substance and when they have a wound, they selectively consume the anti-inflammatory grains. (Danbury et al., 2000)
When a hen acquires knowledge or behaviour, it is propagated and copied by all the hens or the unit of hens. Behaviours are even learned through a screen. (PMAF, n.d.)
Two days after being born, chickens are already able to calculate cognitive quantities of up to 5 items. In addition, they understand the "permanence of the objects," that is, the objects continue to exist when they are not in their field of view, a skill that refines them.
They have the ability to distinguish, between two pictures, the one which depicts the hen they know, even if the photograph shows the animal at a younger age or part of his or her body. (Domken & amp; Zayan, 1998)
Like mammals, hens experience REM (Rapid Eye Movement) sleep, that is, the sleep phase where the brain remains active, allowing the creation of dreams.
They can sleep with one eye closed and the other open, resting half the brain and keeping the other half vigilant.
When sleeping on the perch, those sleeping in the middle sleep with the two eyes closed, while those on both ends sleep with the outer eye open. During the night they will turn 180 degrees to rest the other half of the brain.
They have a social organization
They have a strict social hierarchy, with some animals dominating the rest. Existing chickens mimic the leader's behaviour.
... and complex communication
They use a rich array of sophisticated phonetics to communicate with each other, with over 30 calls and warnings, each with a different meaning. Warning of danger coming from above differs from the warning of a terrestrial threat.
Scientists compare their communication skills with those of some primates.
Under intensive rearing conditions, hens are tortured
Modern hens and chickens have been the subject of intense genetic selection.
A wild hen generates about 20 eggs a year, while the hen of the rearing system generates over 300.
As for chickens, they have undergone such 'maximization' of their muscular mass, their skeleton is unable to respond and their bones bend from the weight of their body.
While wild hens live in small clusters of 20-25 birds, consisting of many females and one male or only males, in the production units, hens and chickens live together by the thousands or tens of thousands, under conditions of extreme collusion that deprive them of the ability to do exactly what their nature and instincts dictate:
To flap their wings, scrape the ground, to peck, to perch, to roll in the soil...
They are tortured by stress, deprivation and boredom and in their anxiety to survive, are overwhelmed and cannibalized.