Chickens

Chickens recognize faces and count, and we kill 215 million a day

By WhyStopHarmingAnimals.com

Chickens are the most killed land animal on Earth. About 78.5 billion were slaughtered in 2024, up from 76.2 billion in 2023, out of 87.9 billion land animals killed in total[1]. That is about 215 million chickens a day, or 150,000 every minute.

They are also far more capable than the way they are farmed would suggest[2]. Hens recognize individuals[2][3], respond to their chicks' distress[5], plan for a better reward, and work out who outranks whom[2]. Chicks only days old can compare quantities and do simple sums[6].

They know who is who

Marino's 2017 review of chicken cognition, published in Animal Cognition[2], sums up decades of research. Chickens recognize individuals, both in person and in photographic slides[2]. They keep social hierarchies and track rankings, make simple social inferences, and have a sense of time[2]. Marino's conclusion is that chickens are not the cognitively simple animals they are sold as[2]. Classic work put the number of flock-mates a hen can tell apart at around 100.

In a 1991 study in Behavioural Processes, Bradshaw trained hens in a Y-maze to tell apart members of their own social group for a food reward, showing they distinguish specific birds rather than a generic "chicken[3]." It was a small study. Hens also learn to recognize particular humans.

Faces matter from the start[4]. In a 2024 study in PNAS, single-cell recordings in one-week-old chicks that had never seen a face found neurons in a higher-order brain area that responded selectively to a face-like arrangement of features[4]. Face perception in chickens does not depend only on learning after hatching[4].

A hen feels her chick's trouble

Edgar and colleagues exposed chicks to a mildly unpleasant puff of air while their mothers watched, safe from it themselves[5]. The hens became more alert, preened less, and showed a drop in eye temperature, a physiological sign of stress[5]. Published in the Proceedings of the Royal Society B in 2011, the study is observational, and the authors described being affected by another's state as a building block of empathy[5].

Numbers and self-control

In a 2015 study in Scientific Reports, Rugani and colleagues found that newly hatched chicks map smaller numbers to the left and larger ones to the right, a spatial number line like the one humans use[6]. Chicks just days old pick the larger of two hidden sets and do simple addition and subtraction with small numbers of hidden objects[6]. They do this without training.

Adult hens show self-control. Given the choice, they will wait six seconds for a 22-second jackpot of food rather than take three seconds of food straight away. Delaying gratification like that requires representing a future reward. Hens also use transitive inference to navigate the peck order: if one bird beats a second, and the second beats you, you avoid picking a fight with the first.

Bred to grow until they are killed

The chickens raised for meat, called broilers, have been bred into a different animal. According to the National Chicken Council, a market broiler in 1925 took about 112 days to reach about 2.5 pounds[7]. Today's birds reach more than 6 pounds in about 47 days[7]. That growth rate comes from selective breeding[7]. The bird was selected for speed, with no regard for the life a chicken would live[7].

Eggs cost lives too

Egg-laying hens come from a separate supply chain, and it is no kinder. Male chicks of laying breeds will never lay eggs and do not grow fast enough to be sold for meat, so on the order of 6 billion a year worldwide are killed shortly after hatching, ground up or gassed, because they have no market use. The hens who do lay are slaughtered when their production drops.

Poultry carries a cost for the people who eat it as well[9]. In an observational competing-risk analysis, eating more than 300 grams of poultry a week was associated with higher all-cause mortality and higher death rates from gastrointestinal cancer[9]. That is a health finding, and it is apart from the question of what chickens feel[9].

Each of the 215 million chickens killed today was a bird who could recognize her flock[2], respond to her chicks[5] and keep track of small numbers[6].