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"What are the natural behaviours of chickens? What behaviour patterns are displayed in caged layer hens, where these natural behaviours are frustrated?"
by Deirdre Sims
In this report I will briefly discuss the history of the chicken and examine what impacts domestication may have had on the behaviours of the modern domestic chicken. I will discuss recognised normal behaviour patterns evident in chickens and examine how these behaviours are frustrated in caged layer hens and what resulting behaviours manifest.
What are the natural behaviours of chickens?
Modern domestic chickens descend from the Red Jungle Fowl of India which has been described as "….the mother of all poultry to the rest of the world…." (Madhav Fitzpatrick & Ahmed, 2000).
There is evidence which documents the domestication of the Red Jungle Fowl (Gallus gallus) in India as early as 2500-2100 BC. Through trade, the bird made its way on to Egypt, Iran, Iraq, Asia Minor, Greece and the Roman Empire (Madhav Fitzpatrick & Ahmed). The bird was celebrated for its beauty and courage. Brilliant red, brown, green, gold and black feather plumage ends with an elaborate tail which is described as an eclipse plume.
Domestic chickens today may appear physically different from these glamorous ancestors, yet they continue to exhibit the same behavioural patterns and instincts displayed by the Red Jungle Fowl. "Neither thousands of years of domestication nor the recent extreme selective breeding for productivity have significantly altered the biological and behavioral characteristics of these birds" (Folsch et al, 2002).
Fölsch, Höfner, Staack and Trei have identified six basic behavioural expressions evident in chickens. These are foraging behaviour, locomotive behaviour, resting behaviour, maintenance-comfort behaviour, social behaviour and the nesting-laying behaviour sequence (2002).
Foraging behaviour is where a chicken will peck and scratch at the ground with its beak in order to find food from which it will gain essential nutrients. Chickens will spend most of the day foraging, even in domestic conditions where food is readily available (Farm Sanctuary, 2001).
Locomotive behaviour is the performance of basic movements such as walking, running, flying, fluttering and wing flapping and stretching. Hens have been documented walking up to 1.5 km a day (Folsch et al, 2002). Through personal experience observing chickens, I have seen them display continuous locomotive behaviour during their waking hours. They will walk, foraging as they go, run and fly onto elevated perches, play fight with each other, scratch and dustbathe.
Resting behaviour consists of standing, sitting, sleeping and roosting.
Maintenance-Comfort behaviour involves "preening, stretching, flapping, dustbathing, sunbathing and body shaking" (Folsch et al).
Preening involves burrowing their beaks into their plumage and assists in the maintenance of feather condition.
Dustbathing is a highly motivated behaviour (Lindberg & Nicol, 1997) in chickens and also assists with maintaining good feather condition. This activity involves ‘bathing’ and scratching in dry earth, effectively spraying dry dust onto and into their feather plumage. Dustbathing can be described "as having three stages: tossing, rubbing, and shaking; all in an attempt to regulate feather condition by removing excess oils" (Farm Sanctuary, 2001).
I have observed chickens sunbathing. They appear to appreciate the warmth of the sun and look quite serene as they soak up the rays. However, sunbathing has biological benefits for chickens also. Folsch et al state:
'Daylight controls and triggers many of their physiological processes. It also stimulates their metabolism, plays an important part in the formation of red and white blood cells and of vitamin D, and promotes the secretion of hormones necessary for growth and reproduction' (2002).
"Pecking, threatening, chasing, kicking, fighting, avoiding, crouching and vocalizing" (Folsch et al) are expressions of social behaviour and interaction. Wild chickens form structural communities with different hierarchical levels. Typically a flock will consist of a small group of hens and a single rooster. I have seen domestic chickens form structured cohesive communities, even in a single sex environment.
Folsch et al describe hens engaging in the nesting-laying behaviour sequence as follows:
'Separating from the flock, examining potential nest sites, scratching and pecking at nest material, building a nest or choosing an already formed nest, entering the nest, forming a hollow, laying an egg, rolling the egg under the body, lying on the egg, getting up, standing, leaving the nest and cackling' (2002).
The instinct in hens to nest is extremely strong. ‘Willingness to work experiments’ have seen hens walk through air blasts and shallow water baths, as well as push through weighted swing doors (Morris, 2005) in order to reach a nest.
What behaviour patterns are displayed in caged layer hens, where these natural behaviours are frustrated?
It has been scientifically recognised that chronic psychological and physical suffering often leads to abnormal ‘stereo-typical’ behaviour in animals. In caged layer hens, abnormal behaviour manifests itself in various forms, the most documented of which include feather peaking, cannibalism, vacuum dustbathing, vacuum nesting and high levels of hysteria, fear and aggression. Some of the factors of caged systems which are believed to cause these behaviours include extreme lack of space, total lack of stimuli, low level artificial lighting and a general artificial environment as well as procedures such as debeaking and moult inducement.
According to the Egg Producers Federation of New Zealand, we keep approximately 92% of commercial layer hens in caged production systems. There are approximately 2.8 million layer hens confined to battery cages in New Zealand (2005).
The lack of space in caged systems is perhaps the most significant aspect of such systems which causes abnormal and disturbed behaviour in hens. Lack of space severely restricts ‘comfort’ behaviour such as wing flapping, leg stretching, feather raising and body shaking. Intense crowding and lack of ‘inter-animal’ space in caged systems also throws social structures into disarray, negating the opportunity to form cohesive communities (Farm Sanctuary, 2001).
In the battery cage system, each hen will have the physical space approximately equivalent to that of an A4 piece of paper. In a Farm Sanctuary report it was stated that "…general freedom of movement is generally associated with the freedom to perform specific behavior patterns" (2001). In commercial caged systems, there can be no denying that hens are severely deprived of space.
In their 2002 Code of Welfare submission for layer hens, the SPCA called for an immediate phase out of the battery cage system, with a complete ban in place by 2010. In their submission they also stated that caged systems led to the inability of hens to carry out natural patterns of behaviour which caused psychological suffering as well as physical pain and discomfort to the hens (SPCA).
Feather pecking is a form of violent and aggressive behaviour that is commonly displayed by caged hens. This behaviour can be seen as a displacement behaviour resulting from barren environments. The severe lack of space and total absence of stimuli in caged systems causes the hens to redirect (or misdirect) their strong natural instinct to peck and forage towards their cage-mates. This results in injury and pain, reduced feather coverage, heat loss and sometimes cannibalism (Farm Sanctuary, 2001).
Studies have shown that when hens in cages have been provided with forms of stimuli such as coloured string, babies’ toys or straw and litter, violent feather pecking decreased dramatically (Morris, 2005). These things provided some enrichment in an otherwise barren environment by giving the hens something to peck at other than their cage-mates.
Feather pecking has also been shown to manifest itself in conditions which make no provision for dustbathing (Vestergaard et al, 1993). These types of conditions also lead to an abnormal behaviour which is termed ‘vacuum dustbathing’. The motivation in hens to dustbathe is so strong that they will carry out the motions of this behaviour on the wire bottoms of their cages (Farm Sanctuary, 2001).
Frustration and chronic suffering results in caged hens that do not have the opportunity to dustbathe (Baxter, 1994). Experiments have been carried out where caged hens have been given access to sand and litter. It has been observed that these hens seem to ‘make up for lost time’ by dustbathing for extended periods of time. This has been termed the ‘rebound effect’ (Norgaard-Nielsen, 1997). Appleby et al have stated that dustbathing has physical and behavioural benefits for hens and is a "significant contribution to the welfare of laying hens" (1993).
Caged hens are also completely deprived of the ability to nest. They are given no nesting space or materials. Their eggs are laid on the sloping wire of the cage bottom. The slope enables the eggs to roll down out of the cage where an egg collector collects them or where a conveyer belt carries them away. Farm Sanctuary have stated in their 2001 report that hens may exhibit very disturbed behaviour if a nest is not available to them during their pre-laying period. Aspects of this behaviour include restlessness and agitation as well as ‘vacuum nesting’, where the hen will attempt to sit and carry out the movements of nesting in her barren environment.
The above behaviours are obvious indications of severe frustration. The motivation to nest in hens is so intense that the inability to do so is likely to cause acute suffering (Baxter, 1994), therefore contributing to welfare problems for caged hens.
Appleby and Hughes (1995) carried out several experiments were caged hens were given access to nests. There experiments showed that 91-96% of eggs were laid in the nest box provided. In similar experiments, Smith et al (1993) discovered that pre-laying behaviour in caged hens was the least disturbed when provided with nest boxes, intermediately disturbed when provided with dustbaths and the most disturbed when in a barren cage (Farm Sanctuary, 2001).
All of the above mentioned circumstances lead to increased levels of fear, hysteria and aggression in caged layer hens. Appleby has documented fear and hysteria in caged hens resulting from exposure to humans and other unfamiliar elements. In his studies of hens in other systems such as percheries and free-range farms, he found fear and hysteria responses to such stimuli to be absent (1991). It may be surmised that this is because "the battery cage system puts hens in a perpetual state of physical and psychological suffering" (Farm Sanctuary, 2001).
It has become evident to me during the writing of this report that the battery cage system disallows hens to perform the most basic behaviours. Inside a battery cage, a hen cannot walk, fly, run, stretch her wings, dustbathe, forage, nest or perch. Additionally, she cannot engage in more complex behaviours such as belonging to, and helping to form, a cohesive social community. These behavioural restrictions lead to frustration and psychological suffering in hens. Hence abnormal behaviours occur.
Science has showed that hens have a very strong motivation to perform behaviours that are natural to them. Performance of their natural behaviours benefits them both physically and psychologically. When hens are confined to the battery cage system and they are unable to perform natural behaviours, abnormal behaviours arise due to frustration and psychological disturbance.
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