Sham dustbathing is a behaviour performed by some birds when kept in cages with little or no access to litter, during which the birds perform all the elements of normal dustbathing, but in the complete ''absence'' of any substrate.Olsson, I.A.S., Keeling L.J. and Duncan, I.J.H., 2002. Why do hens sham dustbathe when they have litter? Applied Animal Behaviour Science, 76: 53–64Merrill, R.J.N., Cooper, J.J., Albentosa M.J. and Nicol, C.J., 2006. The preferences of laying hens for perforated Astroturf over conventional wire as a dustbathing substrate in furnished cages. Animal Welfare, 15:173–178van Liere, D.W., 1992. The significance of fowls' bathing in dust. Animal Welfare, 1:187–202 This behaviour often has all the activities and temporal patterns of normal dustbathing, i.e. the bird initially scratches and bill-rakes at the ground, then erects its feathers and squats. Once lying down, the behaviour contains four main elements: vertical wing-shaking, head rubbing, bill-raking and scratching with one leg. Normal dustbathing is a maintenance behaviour whose performance results in dust collecting between the feathers. The dust is then subsequently shaken off which reduces the amount of feather

lipid Lipids are a broad group of naturally-occurring molecules which includes fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids incl ...

s and so helps the plumage maintain good insulating capacity and may help control of

ectoparasites Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson ha ...

.Olsson, I.A.S. and Keeling, L.J., 2005. Why in earth? Dustbathing behaviour in jungle and domestic fowl reviewed from a Tinbergian and animal welfare perspective. Applied Animal Behaviour Science, 93: 259-282

Terminology

Sham dustbathing is sometimes referred to as "vacuum dustbathing". In the

Konrad Lorenz Konrad Zacharias Lorenz (; 7 November 1903 – 27 February 1989) was an Austrian zoologist, ethologist, and ornithologist. He shared the 1973 Nobel Prize in Physiology or Medicine with Nikolaas Tinbergen and Karl von Frisch. He is often rega ...

model of behaviour regulation, vacuum activities occur when motivation for a certain behaviour builds to a sufficiently high level that the behaviour is performed in the complete absence of relevant stimuli. However, hens "dustbathing" on wire floors commonly perform this close to the feed trough where they can peck and bill-rake in the food.Lindberg, A.C. and Nicol, C.J. 1997. Dustbathing in modified battery cages: is sham dustbathing an adequate substitute? Applied Animal Behaviour Science, 55: 113–128 Because it seems the birds appear to treat the feed as a dustbathing substrate, the term "sham dustbathing" is more appropriate.

Motivational basis

Sham dustbathing, like normal dustbathing, appears to have both internal and external causal factors.

Internal causal factors

Under unrestricted conditions, adult birds dustbathe about every second day, with a diurnal rhythm peaking in the middle of the day, and an average dustbathing bout lasting about 27 minutes. Hens without litter (i.e. an absence of external causal factors) will perform sham dustbathing with a similar temporal pattern. Some hens deprived of litter until they had developed sham dustbathing and then given access to litter, showed sham dustbathing although litter was available. Thus, there is some support for an effect of habit or early experience on sham dustbathing. Depriving hens of the opportunity to dustbathe results in a rebound when hens are again allowed access to dust. Birds work for access to litter, in which case they sometimes, although not always, dustbathe. There are indications of stress when hens are deprived of the possibility to dustbathe, and if this deprivation is sufficiently long, sham dustbathing behaviour develops.

External causal factors

It has been suggested that the sight of other hens performing the behaviour increases the probability of sham dustbathing, i.e. social facilitation; however, when tested, the sight of stimulus birds had no effect on the sham dustbathing behaviour of test birds. As indicated above, hens "dustbathing" on wire floors commonly perform this close to the feed trough where they can peck and bill-rake in the food, indicating this may be an external causal factor.

Welfare

Sham dustbathing raises an interesting question in animal behaviour, motivation and welfare. Hens that have been reared in captivity without ever having encountered litter will perform sham dustbathing.Wichman, A. & Keeling, L.J., 2008. Hens are motivated to dustbathe in peat irrespective of being reared with or without a suitable dustbathing substrate. Animal Behaviour, 75: 1525-1533 Therefore, it can be questioned how these birds, which have never had the possibility to dustbathe in a functional substrate, perceive sham dustbathing; do they yearn for something that they have never had or known (i.e. litter), or are they content to sham dustbathe? A weighted push-door was used as the

operant Operant conditioning, also called instrumental conditioning, is a learning process where behaviors are modified through the association of stimuli with reinforcement or punishment. In it, operants—behaviors that affect one's environment—are c ...

method to quantify motivation to dustbathe in adult hens with different previous experiences of litter. There was no difference between hens in the weight of doors they pushed open to gain access to peat. Hens that had no previous experience of peat were as motivated to work to gain access to this substrate as birds used to dustbathing in peat. This implies that sham dustbathing is not satisfying to the hen nor is it perceived as normal dustbathing.

References