Social influences on the comfort behaviour of laying hens

Applied Animal Behaviour Science, 22 (1989) 75-81

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Elsevier Science Publishers B.V., Amsterdam - - Printed in The Netherlands

S o c i a l I n f l u e n c e s on the C o m f o r t B e h a v i o u r of Laying Hens C.J. NICOL

Department o[ Animal Husbandry, Langford House, Langford, Bristol BS18 7DU (Gt. Britain) (Accepted for publication 5 September 1988)

ABSTRACT Nicol, C.J., 1989. Social influences on the comfort behaviour of laying hens. Appl. Anita. Behav. Sci., 22: 75-81. The influence of the visibility and proximity of familiar pen mates on the behaviour of laying hens was examined. Tail wagging counts increased when pen mates were visible, whilst counts of body shaking and preening increased when pen mates were in close proximity. Head shaking counts were higher when pen mates were visible and at close proximity than when they were hidden and at a minimum distance of 1 m. The influence of social status on comfort behaviour performance was examined in three laying flocks. Individuals within each flock were ranked on three scales measuring dominance, aggression and social interactiveness. Correlations between these social indices and the performance of comfort behaviour were obtained. There were significant negative correlations between dominance and rate of wing flapping in three flocks, and between aggression and wing flapping in two flocks. Additional negative correlations between body shaking and dominance, body shaking and aggression, head scratching and dominance, and preening and aggression were noted in one flock each. There were no significant correlations between interactiveness and comfort activity performance.

INTRODUCTION A n u m b e r of activities of l a y i n g h e n s have been g r o u p e d t o g e t h e r a n d t e r m e d " c o m f o r t b e h a v i o u r " , on t h e a s s u m p t i o n t h a t t h e i r f u n c t i o n is m a i n l y to m a i n t a i n p l u m a g e or s t r e t c h muscles. T h e s e activities include w i n g / l e g stretching, wing flapping, b o d y shaking, f e a t h e r raising, p r e e n i n g a n d h e a d s c r a t c h i n g ( B l a c k a n d H u g h e s , 1974). K r u i j t (1964) includes tail wagging as a c o m f o r t a c t i v i t y in jungle fowl. H o w e v e r , t h e s e activities m a y serve f u n c t i o n s addit i o n a l to i m p r o v i n g p h y s i c a l c o m f o r t . T h e social e n v i r o n m e n t , in p a r t i c u l a r , m a y provide stimuli w h i c h influence t h e i r p e r f o r m a n c e ( T i n b e r g e n , 1952). T h e objectives of this s t u d y were to e x a m i n e t h e effects of t h e p r e s e n c e of familiar c o m p a n i o n s a n d social s t a t u s on c o m f o r t b e h a v i o u r p e r f o r m a n c e .

76 MATERIALS AND METHODS

Experiment I Ten Warren hens, which had been reared on litter and housed together in a pen 2.4 × 2.4 m from 18 weeks of age, were used for this experiment. The birds were 24 weeks of age at the start of the experiment. The home pen contained a commercial feeder, waterer and nest boxes. These fittings did not allow perching behaviour. Food was available ad libitum and the pen was lit from 06.00 to 20.00 h daily (14L: 10D ). To assess the influence of the proximity and visibility of familiar pen mates on behaviour, each bird was placed in turn into a large-gauge wire-mesh cage, 0.70 × 0.75 × 0.75 m in height, with a litter floor, and ad libitum food and water. This cage size did not physically restrict any of the activities under examination. The behaviour of each bird was observed continuously from 14.00 to 16.00 h under three conditions of social contact. Firstly, the cage was sited within the home pen so that pen mates were visible and in close proximity to the subject bird. Secondly, the cage was sited at a distance of 1 m from the home pen so that pen mates were visible, but at a minimum distance of 1 m from the subject bird. Thirdly, the cage was sited at a distance of 1 m from the home pen and a hardboard partition was erected so that the pen mates were no longer visible to the subject bird. A randomised block design ensured that each bird was tested once under each condition of social contact. Counts of 21 activities were taken and bout lengths recorded where applicable. Nineteen activities were described by Nicol (1987a). In this experiment, litter pecking, where the hen pecked at loose material on the cage floor, and alert standing, where the hen stood with an erect posture and eyes fully open, were also recorded. Data for each activity were tested for normality. Count data were then subjected to square root transformation to reduce correlation between means and error variance. Bout length data, i.e., proportions of time spent in each activity in a 2-h observation period, were subjected to arcsine transformation (Sokal and Rohlf, 1981). Analysis of variance was performed to test for significant differences between the three treatments. The treatment means of activities shown to be significantly affected by social contact were further examined by Tukey's T-method.

Experiment 2 Social relationships were examined amongst three flocks of Warren hens, housed on litter in pens 2.1 X 4.4 m. Each pen was provided with a commercial feeder and waterer and six nest boxes, which birds could not perch or fly onto. Flock 1 comprised 23 individuals aged 24 weeks, housed together for 6 weeks prior to the first observations. Flock 2 comprised 23 individuals aged 30 weeks,

77 housed together for 12 weeks prior to observation. Flock 3 comprised 19 individuals aged 54 weeks, housed together for 6 weeks prior to observation. Individual birds were identified with coloured plastic leg rings. Observations on each flock were taken for 1 h in the morning and 1 h in the afternoon for 5 consecutive days. The identity of each bird involved in a dyadic agonistic encounter, characterised by pecks, threats or avoidances, was recorded. The identity of each bird performing wing/leg stretching, wing flapping, body shaking, feather raising, tail wagging, preening or head scratching was also recorded. Wing flapping was only recorded when it was performed by a stationary bird and not when it occurred during chase or escape sequences. Three measures reflecting social relationships were calculated from the data on agonistic encounters. Firstly, birds were ranked according to the number of other birds they dominated. The assumption that dominance was generally transitive within each flock was tested and a rank order for each flock constructed so as to minimise reversals where individuals dominated others higher in the rank. Secondly, birds were ranked on an aggression scale by calculating the number of threats or pecks delivered by each hen. This index was logically distinct from that of dominance since even low ranking individuals may be particularly aggressive towards the few individuals subdominant to themselves (Craig, 1986). Thirdly, birds were ranked according to the total number of agonistic encounters they were involved in, as both winners and losers. This provided an index of the relative interactiveness of each bird within the flock. The relationships between each social index and the performance of comfort behaviour were examined using Spearman rank correlation coefficients. RESULTS

Experiment 1 Birds made no apparent attempts to escape from the experimental cage during this experiment and no stereotyped pacing was involved. The rate of performance of six activities was significantly affected by the degree of social contact birds had with their pen mates (Table 1 ). Tail wagging and drinking counts were significantly higher when companion birds were visible, whilst preening and body shaking counts were significantly higher when companion birds were in close proximity. Head shaking counts were higher and cage pecking counts were lower when companions were visible and in close proximity than when they were hidden and at a minimum distance of 1 m. There were no significant effects of social contact on the bout lengths of any activity.

Experiment 2 Dominance was established for 86 out of 253 possible relationships in Flock 1, for 106 out of 253 relationships in Flock 2 and for 107 out of 171 relationships

78 TABLE1 Effect of social contact with p e n mates on activity performance Activity

Feed Drink S t a n d alert S t a n d rest Sit Walk Wing/leg stretch Head stretch Wing flap Body shake Feather raise Tail wag Head shake Preen Dust b a t h e Scratch floor Head scratch Cage peck Litter peck Yawn Beak wipe

Activity counts in 2 h 1 Visual contact 0 m distance

Visual contact I m distance

No visual contact I m distance

2

SD

x

SD

2

SD

30.5 17.9 18.8 0.5 3.0 18.4 1.6 3.2 0.3 1.9 1.4 3.8 16.9 10.9 1.0 22.4 7.0 0.9 18.2 1.3 2.3

16.6 9.4 a 10.6 1.1 4.8 14.6 1.4 3.5 0.7 1.6 a 2.7 3.1 a 8.5 a 7.0 a 1.5 24.7 6.3 1.0 a 22.3 1.2 2.4

35.2 18.8 20.6 0.6 1.6 26.9 1.8 2.7 0.4 0.7 0.2 4.2 15.1 5.1 0.5 41.3 5.0 2.5 32.6 1.4 2.3

19.0 10.2 a 19.3 1.3 2.0 17.3 2.4 5.6 0.7 0.5 b 0.6 2.4 a 14.0 ab 3.35 1.1 46.2 3.8 2.2 ab 39.1 2.1 4.1

22.3 9.0 25.0 0.9 1.6 20.4 0.6 6.6 0.1 0.8 0.0 1.1 7.1 3.6 0.4 14.5 3.4 4.4 22.9 0.7 0.4

11.1 5.25 19.0 1.5 2.3 19.0 1.6 5.4 0.3 1.35 0.0 1.55 6.65 4.4 I' 1.0 21.8 3.6 4.45 26.5 0.9 0.7

~Activity counts are expressed as u n t r a n s f o r m e d arithmetic means (10 birds) a n d s t a n d a r d deviations u n d e r three social conditions. a'bMeans in the same row with different superscripts differ significantly ( P < 0.05 ).

in Flock 3. The assumption that transitivity of dominance was greater than expected by chance was tested using the procedure given by Appleby (1983), adapted from Kendall (1962). Highly significant degrees of dominance transitivity were established for all flocks ()~z _- 69.2, df 29.4, P<0.001; 68.1, df 29.4, P < 0.001; 72.7, df 25.8, P < 0.001 for Flocks 1-3, respectively). The coefficients of linearity, K, for the hierarchy within each flock were 0.31, 0.30 and 0.46, for Flocks 1-3, respectively. Spearman rank correlations between comfort behaviour and measures of dominance, aggression and interactiveness were performed for wing flapping, tail wagging, preening, head scratching and body shaking (Table 2). There were insufficient data for meaningful correlations to be made for wing/leg stretching, wing raising and feather raising. Significant negative correlations

79 TABLE 2 Spearman rank correlation coefficients (rs) between comfort activity performance and measures of dominance, aggression and interactiveness Activity

Wingflap Body shake Tail wag Preen Head scratch

Dominance

Aggression

Interactiveness

Flock 1

Flock2

Flock3

Flock 1

Flock2

Flock3

Flock 1

Flock2

Flock3

-0.37* -0.38* +0.03 +0.11 +0.07

-0.39* +0.07 -0.32 -0.21 -0.41"

-0.42* +0.11 -0.22 -0.29 +0.30

-0.29 -0.42* +0.02 +0.03 +0.07

-0.36* +0.11 -0.33 -0.21 -0.18

-0.51" +0.04 -0.11 -0.50* 4-0.01

-0.06 -0.11 -0.25 -0.06 -0.19

+0.02 +0.07 +0.27 +0.14 -0.18

+0.05 -0.09 -0.08 -0.12 -0.19

*Significant at P < 0.05.

were found between wing flapping and dominance in all three flocks, i.e., less dominant birds had higher rates of wing flapping. In Flock 1, there was a significant negative correlation between body shaking and dominance, and in Flock 2, a significant negative correlation between head scratching and dominance. Less aggressive birds also performed more wing flapping in Flocks 2 and 3, more body shaking in Flock 1 and more preening in Flock 3. There were no significant correlations between interactiveness and comfort activity performance. DISCUSSION

Much remains to be learnt about the causation of comfort behaviour in the laying hen despite the fact that such knowledge is considered important for welfare assessment (Hughes, 1980; Duncan, 1981). Nicol (1987b) reported that wing/leg stretching, wing flapping, tail wagging and preening increased dramatically in rate after prevention by spatial restriction, indicating a strong internal component to their motivation. However, social factors may also influence the performance of some comfort activities. Hughes (1983) considered the social factors involved in the causation of head shaking and Eskeland (1977) found a negative correlation between dominance and preening in caged birds. The results of Experiment 1 support Hughes' (1983) hypothesis that head shaking is an alerting response which occurs in situations demanding increased attention. Tail wagging was also more frequent when companion birds were visible. This activity may simply express the emotional state of the performer (Wood-Gush, 1987), which may itself be altered by the visibility of other birds. It could also be a social signal, but further work is needed to determine the responses of other birds to the performance of this activity. Preening and body shaking counts were higher when birds were in close

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proximity to their pen mates than when they were at least 1 m apart. Keeling and Duncan (1985) found that hens in a semi-natural environment tended to form more compact flocks when the major flock activity was preening and suggested that the behaviour of birds was important in determining their spacing patterns. Experiment 1 indicated that spacing may correspondingly determine behaviour. A bird in enforced close proximity to another may actually have an increased motivation to preen or body shake. Wood-Gush (1956, 1971 ) found that wing flapping frequently occurred as a displacement activity in male birds during courtship or agonistic encounters. The correlations between increased wing flapping with low dominance or aggressive social status in Experiment 2 suggest that this activity may also frequently occur as a displacement activity in female flocks. The six nest boxes provided for each flock were unlikely to have been monopolised by dominant birds (Banks et al., 1979 ), but subordinate birds may have been denied access to the feeder and shown increased wing flapping as a response to frustration or conflict. This hypothesis is supported by the observation that most wing flapping occurred in the corner of the pen furthest from the feeder. Less aggressive birds performed more preening in Flock 3. This may also have been a consequence of thwarting or conflict, although the preening bouts did not appear frantic or hurried, as is characteristic of displacement preening (Duncan and Wood-Gush, 1972). It may be, therefore, that less aggressive birds are more motivated to preen simply because they congregate closer together. In these experiments, the visibility and proximity of familiar companions appeared to have more effect on comfort behaviour performance than the social status of individuals within the flock. These preliminary results should be extended to take account of the more complex social relationships which exist amongst birds (e.g., Zayan and Duncan, 1987). However, the fact that preening, body shaking and tail wagging appeared to be stimulated by the sight or close proximity of other birds should be considered in relation to the welfare of birds housed in cages where these activities are difficult to perform (Nicol, 1987b).

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81 Eskeland, B., 1977. Behaviour as an indicator of welfare in hens under different systems of man-. agement, population density, social status and by beak trimming. Meld. Nor. Landbruksh.oegsk., 56: 1-20. Hughes, B.O., 1980. The assessment of behavioural needs. In: R. Moss (Editor), The Laying Hen and its Environment. Martinus Nijhoff, The Hague, pp. 149-160. Hughes, B.O., 1983. Headshaking in fowls: the effect of environmentalstimuli. Appl. Anim. Ethol., 11: 45-53. Keeling, L.J. and Duncan, I.J.H., 1985. Some factors influencing spacing in domestic fowl in a semi-natural environment. In: R. Zayan (Editor), Social Space for Domestic Animals. Martinus Nijhoff, Dordrecht, pp. 27-37. Kendall, M.G., 1962. Rank Correlation Methods. Charles Griffin, London. Kruijt, J.P., 1964. Ontogeny of social behaviour in Burmese red junglefowl (GaUusgaUus spadiceous). Behaviour, Suppl. 12, 1-201. Nicol, C.J., 1987a. Effect of cage height and cage area on the behaviour of hens housed in battery cages. Br. Poult. Sci., 28: 327-335. Nicol, C.J., 1987b. Behavioural responses of laying hens following a period of spatial restriction. Anim. Behav., 35: 1709-1719. Sokal, R.R. and Rohlf, F.J., 1981. Biometry. The Principles and Practice of Statistics in Biological Research. Freeman, San Francisco, 859 pp. Tinbergen, N., 1952. Derived activities, their causation, biological significance, origin and eman-. cipation during evolution. Q. Rev. Biol., 27: 1-32. Wood-Gush, D.G.M., 1956. The agonistic and courtship behaviour of the brown leghorn cock. Br. J. Anim. Behav., 4: 133-142. Wood-Gush, D.G.M., 1971. The Behaviour of the Domestic Fowl. Heinemann, London, 147 pp. Wood-Gush, D.G.M., 1987. Awareness and self-awareness in the domestic fowl and their relation ship to animal welfare. In: R. Zayan and I.J.H. Duncan (Editors), Cognitive Aspects of Social Behavior in the Domestic Fowl. Elsevier, Amsterdam, pp. 34-39. Zayan, R. and Duncan, I.J.H. (Editors), 1987. Cognitive Aspects of Social Behaviour in the Domestic Fowl. Elsevier, Amsterdam, 492 pp.