Why in earth? Dustbathing behaviour in jungle and domestic fowl reviewed from a Tinbergian and animal welfare perspective

Abstract

Dustbathing has been the subject of much research in captive birds. In the present review we bring together the studies of domestic fowl (Gallus gallus domesticus) and jungle fowl (Gallus gallus) to provide a more complete picture of the behaviour. Dustbathing is discussed from the four aspects suggested by Tinbergen (1963): ontogeny, phylogeny, function and causation and a general aim is to give as complete review as possible of research on dustbathing behaviour.

Studies of ontogeny of dustbathing show that early substrate experience affects later preferences. It appears nevertheless as though the behaviour develops more or less normally even in the absence of appropriate dustbathing stimuli. The behaviour itself is described for a number of species, and there are experimental studies of dustbathing in both jungle fowl and domestic fowl, but there is little comparative research which could provide hypotheses about the phylogeny of the behaviour. Similarly, despite extensive discussions about the function of dustbathing behaviour and the many suggestions regarding the survival value of performing the behaviour, few studies have actually addressed this question. It has been demonstrated that dustbathing reduces the amount of feather lipids, thereby increasing the insulation capacity of the plumage, but other suggested functions, such as control of ectoparasites, have not been tested experimentally.

The majority of studies of dustbathing behaviour address the question of causation. Dustbathing shows a clear diurnal rhythm and under unrestricted conditions, hens dustbathe about every two days. Birds deprived of litter show a rebound in dustbathing behaviour when litter is again made available, suggesting an increase in motivation after deprivation and so an influence of internal factors With respect to external factors, it has long been believed that dustbathing is socially facilitated, but this has been questioned in recent studies. The presence of a suitable substrate is an important stimulus for eliciting dustbathing, and hens seem to prefer substrates with a fine structure such as sand and peat. Dustbathing is further increased if the substrate is combined with light and heat. The question of whether or not hens are motivated to dustbathe has important consequences for bird welfare in commercial housing systems, but motivational studies give somewhat conflicting evidence. In the final part of this review, both normal litter dustbathing and ‘sham’ dustbathing in the absence of litter are discussed from a welfare perspective.