Behavioural Needs

The behavioural needs of hens

All animals have strong instincts to carry out behaviour that is important to their species. In the case of hens, this behaviour includes scratching and pecking the ground, laying eggs in a nest, dustbathing, and normal exercise such as wing flapping.

Modern hens are descended from the Red Junglefowl, and they still have the instincts of this ancestor. Their behavioural needs have not been substantially altered by domestication and generations of selective breeding. This fact has been clearly demonstrated in studies where birds raised under normal commercial conditions were released into the wild. Even though they had never before experienced this environment, they were able to forage for food, roost in trees at night, build nests and raise young (1-2).

This rapid adaptation would not have been possible if hens didn’t still have the instincts and behavioural repertoire of their ancestors.

Space and opportunity for exercise

How much space does a hen need for basic movements such as turning, or comfort behaviours such as preening? To answer this question, some researchers have videoed hens and calculated the space they occupied (3). Here are the results:

Behaviour

Average

Range

Stand

475sqcm

428-592sqcm

Ground scratch

856sqcm

655-1217sqcm

Turn

1272sqcm

978-1626sqcm

Wing stretch

829sqcm

660-1476sqcm

Wing flap

1876sqcm

1085-2606sqcm

Feather ruffle

873sqcm

609-1362sqcm

Preen

1150sqcm

800-1977sqcm



Remember that hens in groups of 3 or more have only 450 sqcm of space, so they can't even stand without pushing up against other hens. They certainly can't ground scratch or flap their wings, nor can they walk freely.

Being unable to exercise the legs and the wings leads to weak bones that break more easily (4-6).

In another study, 31% of battery hens compared to 14% of free range hens had recently broken bones before they were killed (9).

Nests for laying eggs

One of the strongest instincts of a hen is to lay her egg in a nest. Modern hens still have this instinct, as shown when they are released into a natural environment (2). They become very active in the hours before laying and look for a nest site. They scrape a rough nest and sit in it until they lay their egg. This behaviour is triggered by hormones, and still exists in caged hens (10).

In cages, hens become extremely frustrated when they can't find a nest. They show this frustration by pacing and other restless behaviour (11-13). Pacing up and down has been accepted as a sign of frustration since the study where hungry hens were shown food they couldn’t reach. These hens were definitely frustrated, and they showed their frustration by pacing (14). Similarly, they show their frustration at not having a laying nest by pacing.

One researcher has said: " The disquiet caused by the lack of a laying nest is so great that in my opinion and for this reason alone the battery cage must be thought as very inadequate to fulfill the behavioural needs of the laying hen " (15).

Hens are willing to "work" hard and to endure unpleasant experiences to get to a laying nest. They will move through foot baths and blasts of air, or swing doors with increasingly heavy weights. They will work as hard to reach a nest as they do to reach food after a fast of 20 hours (16). They will squeeze through very small spaces to reach a nest, even though they don't like tight spaces (17). Clearly a laying nest is very important to hens, but in a cage they have to lay their egg on the wire floor.

Material for dustbathing

Hens regularly take dustbaths to keep their feathers in good condition - without dustbathing material their feathers become more oily and less fluffy (18).

However, as well as having a physical function, dustbathing is also a behavioural need in hens, so much so that they try to dustbathe on the wire in cages (19). In this case they succeed only in further damaging their feathers (20).

Another indication that dustbathing is a behavioural need is that hens spend more time doing it the longer they have been without suitable material (21). This kind of compensation, "making up for lost time", is characteristic of highly motivated behaviours.

Material to scratch and peck

Red Junglefowl, the ancestors of modern hens, spent 60.6% of the active part of their day pecking the ground, and 34.1% scratching the ground (22). When hens are given their food either easily accessible in a tray or mixed with litter, they still spend the same amount of time feeding because both groups scratch and peck the litter. In other words, all hens forage, even when they don’t need to in order to get food, leading the researchers to conclude (17):
"... pecking in association with food is so much part of natural feeding behaviour of hens that the animals seem to 'need' to peck and scratch even if they are not hungry at all ".

Hens raised in cages are still attracted to litter. Not surprisingly, hens prefer large cages to small cages when given a choice. However, they choose to enter the smallest cages if they have litter on the floor and the larger cages do not (23-25).

Apart from the behavioural importance of litter, allowing hens to express a strong instinct and giving them something to occupy their time, litter to scratch also keeps the feet and claws in better condition. Hens on litter have less foot damage and fewer overgrown or broken claws than hens on wire (20,26).

One of the Five Freedoms is the freedom to express normal behaviour. In the case of hens, this means they must have enough space for normal movements and comfort behaviours, a nest in which to lay eggs, material for dustbathing, and material to scratch and peck. These needs are acknowledged by the European Union in their recent directive, and form the basis of the new laws applying after 2012, when battery cages will be banned in member countries.

References

  1. Wood-Gush D and Duncan I (1976), “Some behavioural observations on domestic fowl in the wild", Applied Animal Ethology , vol 2 (255-260)

  2. Duncan I, Savory C & Wood-Gush D (1978), "Observations on the reproductive behaviour of domestic fowl in the wild", Applied Animal Ethology , vol 4 (29-42)

  3. Stamp Dawkins M & Hardie S (1989), "Space needs of laying hens", British Poultry Science , vol 30 (413-416)

  4. Norgaard-Nielsen G (1990), "Bone strength of laying hens kept in an alternative system, compared with hens in cages and on deep-litter", British Poultry Science , vol 31 (81-89)

  5. Gregory N, Wilkins L, Kestin S, Belyavin C & Alvey D (1991), "Effect of husbandry system on broken bones and bone strength in hens", Veterinary Record , vol 128 (397-399)

  6. Knowles T & Broom D (1990), "Limb bone strength and movement in laying hens from different housing systems", Veterinary Record , vol 126 (354-356)

  7. Parkinson G (1993), "Osteoporosis and bone fractures in the laying hen", Progress report of work at the Victorian Institute of Animal Science, Attwood

  8. Gregory N & Wilkins L (1989), "Broken bones in domestic fowl: handling and processing damage in end-of-lay battery hens", British Poultry Science , vol 30 (555-562)

  9. Gregory N, Wilkins L, Eleperuma S, Ballantyne A & Overfield D (1990), "Broken bones in domestic fowls: effect of husbandry system and stunning method in end-of-lay hens", British Poultry Science , vol 31 (59-69)

  10. Hughes B & Duncan I (1988), "The notion of ethological 'need', models of motivation and animal welfare," Animal Behaviour , vol 36 (1696-1707)

  11. Wood-Gush D (1972), "Strain differences in response to sub-optimal stimuli in the fowl", Animal Behaviour , vol 20 (72-76)

  12. Mills A & Wood-Gush D (1985), "Pre-laying behaviour in battery cages", British Poultry Science , vol 26 (247-252)

  13. Ramos N & Craig J (1988), "Pre-laying behaviour of hens kept in single- or multiple-hen cages", Applied Animal Behaviour Science , vol 19, (305-313)

  14. Duncan I & Wood-Gush D (1972), "Thwarting of feeding behaviour in the domestic fowl", Animal Behaviour , vol 20 (444-451)

  15. Brantas G (1980), "The pre-laying behaviour of laying hens in cages with and without nests", in R Moss (ed) The Laying Hen and its Environment , Martin Nijhoff, The Hague

  16. Duncan I & Kite V (1987), "Some investigations into motivation in the domestic fowl", Applied Animal Behaviour Science , vol 18 (387-388)

  17. Nicol C & Stamp Dawkins M (1990), "Homes fit for hens", New Scientist , March 17 (28-33)

  18. Van Liere D & Bokma S (1987), "Short-term feather maintenance as a function of dust-bathing in laying hens," Applied Animal Behaviour Science , vol 18 (197-204)

  19. Vestergaard K (1987), "Dustbathing of hens with and without access to sand," Applied Animal Behaviour Science , vol 17 (380)

  20. Simonsen H, Vestergaard K & Willeberg P (1980), "Effect of floor type and density onthe integument of egg layers", Poultry Science , vol 59 (2202-2206)

  21. Vestergaard K (1982), "Dust-bathhing in the domestic fowl - diurnal rhythm and dust deprivation", Applied Animal Ethology , vol 8 (487-495)

  22. Stamp Dawkins M (1989), "Time budgets in Red Junglefowl as a baseline for the assessment of welfare in domestic fowl", Applied Animal Behaviour Science , vol 24 (77-80)

  23. Dawkins M (1978), “Welfare and the structure of a battery cage: size and cage floor preferences in domestic hens", British Veterinary Journal , vol 134 (469-475)

  24. Dawkins M (1981), "Priorities in the cage size and flooring preferences of domestic hens", British Poultry Science , vol 22 (255-263)

  25. Stamp Dawkins M (1983), "Cage size and flooring prefernces in litter-reared and cage-reared hens", British Poultry Science , vol 24 (177-182)

  26. Appleby M (1991), "Do hens suffer in battery cages?" A review of the scientific evidence commissioned by the Athene Trust