By Dr. Clive Dalton and ScienceDaily.com
16 November 2008
Senses in Poultry, by Dr. Clive Dalton
- Chick embryos respond to light as early as 17 days after the start of incubation.
- A hen cannot rotate its eye very much but they can see a field of 300°, with a binocular field of 26°.
- Hens follow moving objects by moving their heads.
- Their acuity (sharpness) is good and they have good distance vision.
- Hens characteristically lift their heads before jumping, and tests have shown that they can discriminate between squares, triangles and red and black dots.
- Studies showed newly hatched chicks preferred to peck at blue objects rather than green or orange ones, although orange was preferred before green but not before red.
- Chicks were found to differentiate between red-dyed liquid and blood. Blood was very aversive to them.
- Chicks learn quickly to avoid coloured feed if it makes them ill, and prefer to peck at round rather than flat objects.
- Not much is known about how important smell is to poultry.
- Hens are not keen on food that smells of mould or is sour, so presumably smell is involved in this feed rejection.
- It’s suggested that birds can definitely smell blood.
- Hens don’t have an ear lobe but they have a well-developed ear.
- Calls produced by hens range from 250 Hertz (Hz) (the broody hen “cluck”) to about 3000 Hz (the distress call).
- Studies confirmed hens can hear sounds as high as 8000 Hz.
- Research found that hearing in hens covered a range from 60-11950Hz with highest sensitivity from 815-2000 Hz which is their normal hearing range.
- Hens have about 340 taste buds mainly on the palate and floor of the oral cavity.
- They are rather indifferent to sugars but can detect glucose to about 2.5% in solution.
- They tolerate a range of acid and alkaline tastes, and are sensitive to and avoid salty feeds.
- Taste determines whether a hen accepts or rejects a feed and similarly to water.
- Hens can detect water temperature differences of 2.8°C. They will reject water that rises 5.5°C above their body temperature although they will readily drink freezing water.
- Stroking, rotating and turning hens upside down will immobilise them for various periods of time.
- In this state, although fully alert to their sensory surroundings, they can be conditioned or gentled to humans or other frightening objects.
- After return to normal they will show reduced fear to the conditioned object.
- Touching the back of a hen will often cause it to respond by a sexual crouch, especially if it is low in social rank.
“A group of genes that code for odor receptor proteins is dramatically expanded in the chicken genome a finding that appears to contradict the traditional view that birds have a poor sense of smell.
And, as it turns out, birds might not have such a great sense of taste. When compared with mammals, chickens have a much smaller family of genes coding for taste receptors, particularly those involved in detecting bitter sensations.”