- Email: [email protected]
Inter-individual distances in the domestic hen
381
I n t e r - I n d i v i d u a l D i s t a n c e s in the D o m e s t i c Hen A.D. MILLS, H. LAGADIC and J.M. FAURE
Station de Recherches Avicoles, I.N.R.A., NouziUy, 37380 Monnaie (France)
ABSTRACT Traditional models of the behaviour of domestic hens imply that aggression, competition, dominance and the maintenance of an exclusive personal space are the major factors controlling the way in which birds space themselves. These models meire certain predictions concerning the behaviour of groups of birds. First, dominant birds should attempt to monopolise access to food resources and be intolerant of subordinate birds feeding in their proximity. Second, confinement under conditions which cause personal spaces to overlap should be aversive to the birds. This paper presents the results of three experiments designed to test the validity of these predictions in small groups of hens. In the first experiment, the individual members of groups of three birds were given the opportunity to feed under varying degrees of physical and visual isolation (i.e. at a circular feeder quadratically partitioned with either solid wood, glass or nominal divisions). The type of feeder division had few significant effects on the way in which birds spaced themselves at the feeder. However, in general, birds tended to feed in the same or adjacent quadrants of the feeder. In the second experiment, the effects of denying birds the possibility of feeding together were investigated. Groups of three birds were used. Two of the birds were placed in a cage located at one end of their home pen. An identical cage was placed at the opposite end of the pen. The third bird was left free in the pen. After the birds had been deprived of food for 6 h, a food trough was placed in front of each cage. In the control test, the trough placed in front of the cage containing the two birds was accessible to all three birds. In the experimental test, the third bird was prevented from feeding at the feeder in front of the cage containing the other two birds by a wiremesh screen, and could only feed at the opposite end of the pen. In the experimental test, the third bird showed a very highly significant reduction in feeding time ( - 2 3 % ; P<0.001) and highly significant increases ( P < 0.001 ) in the numbers of preening bouts, steps taken and movements from one end of the pen to the other. In the third experiment, operant conditioning techniques were used to determine if birds would "work" in order to obtain an increase in cage size. Groups of four birds were kept in cages which had a minimum size of 1600 cm 2. However, by repeated key pecking the birds could increase the cage size, by increments of 450 cm 2, up to a maximum size of 6100 cm2.The birds did not appear to be particularly motivated to work for increased cage sizes and, on average, spent 41% of their time in the minimum-size cages. Furthermore, when the birds did work for increased cage size there was tentative evidence that they tended to avoid cage sizes of approximately 4000 cm 2 (i.e. 1000 cm 2 per bird). None of the results of the three experiments described above were consistent with the premise that dominance and the maintenance of an exclusive personal space are the major factors controlling the way in which birds space themselves. It is therefore suggested that, at least in small groups of hens, these concepts are of limited value.
I n t e r - I n d i v i d u a l D i s t a n c e s in the D o m e s t i c Hen A.D. MILLS, H. LAGADIC and J.M. FAURE
Station de Recherches Avicoles, I.N.R.A., NouziUy, 37380 Monnaie (France)
ABSTRACT Traditional models of the behaviour of domestic hens imply that aggression, competition, dominance and the maintenance of an exclusive personal space are the major factors controlling the way in which birds space themselves. These models meire certain predictions concerning the behaviour of groups of birds. First, dominant birds should attempt to monopolise access to food resources and be intolerant of subordinate birds feeding in their proximity. Second, confinement under conditions which cause personal spaces to overlap should be aversive to the birds. This paper presents the results of three experiments designed to test the validity of these predictions in small groups of hens. In the first experiment, the individual members of groups of three birds were given the opportunity to feed under varying degrees of physical and visual isolation (i.e. at a circular feeder quadratically partitioned with either solid wood, glass or nominal divisions). The type of feeder division had few significant effects on the way in which birds spaced themselves at the feeder. However, in general, birds tended to feed in the same or adjacent quadrants of the feeder. In the second experiment, the effects of denying birds the possibility of feeding together were investigated. Groups of three birds were used. Two of the birds were placed in a cage located at one end of their home pen. An identical cage was placed at the opposite end of the pen. The third bird was left free in the pen. After the birds had been deprived of food for 6 h, a food trough was placed in front of each cage. In the control test, the trough placed in front of the cage containing the two birds was accessible to all three birds. In the experimental test, the third bird was prevented from feeding at the feeder in front of the cage containing the other two birds by a wiremesh screen, and could only feed at the opposite end of the pen. In the experimental test, the third bird showed a very highly significant reduction in feeding time ( - 2 3 % ; P<0.001) and highly significant increases ( P < 0.001 ) in the numbers of preening bouts, steps taken and movements from one end of the pen to the other. In the third experiment, operant conditioning techniques were used to determine if birds would "work" in order to obtain an increase in cage size. Groups of four birds were kept in cages which had a minimum size of 1600 cm 2. However, by repeated key pecking the birds could increase the cage size, by increments of 450 cm 2, up to a maximum size of 6100 cm2.The birds did not appear to be particularly motivated to work for increased cage sizes and, on average, spent 41% of their time in the minimum-size cages. Furthermore, when the birds did work for increased cage size there was tentative evidence that they tended to avoid cage sizes of approximately 4000 cm 2 (i.e. 1000 cm 2 per bird). None of the results of the three experiments described above were consistent with the premise that dominance and the maintenance of an exclusive personal space are the major factors controlling the way in which birds space themselves. It is therefore suggested that, at least in small groups of hens, these concepts are of limited value.