 Behavioural studies showed that when turning, hens used 540 to 1006 cm2, when stretching wings 653 to 1118 cm2, when wing flapping 860 to 1980 cm2, when feather ruffling 676 to 1604 cm2, when preening 814 to 1240 cm2, and when ground scratching 540 to 1005 cm2.A space allowance of 550 cm2 would prevent hens in battery cages from performing these behaviours without touching another hen.Animal welfare scientists have been critical of battery cages because of these space restrictions and it is widely considered that hens suffer boredom and frustration when unable to perform these behaviours.