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Repeated exposure of the domestic chick to a novel environment: Effects on behavioural responses
163 Behauioural Processes, 2 (1977) 163-173 0 Elsevier Scientific Publishing Company, Amsterdam - Printed in The Netherlands
REPEATED EXPOSURE OF THE DOMESTIC CHICK TO A NOVEL ENVIRONMENT: EFFECTS ON BEHAVIOURAL RESPONSES
R.B. JONES Agricultural Research Council’s Poultry Research Road, Edinburgh EH9 3JS (Great Britain)
Centre, King’s Buildings,
West Mains
(Received 19 January 1977)
ABSTRACT Jones, R.B., 1977. Repeated exposure of the domestic chick to a novel environment: effects on behavioural responses. Behav. Processes, 2: 163-173. Seven-day-old male and female chicks of three strains were placed individually in an open field or novel environment for 15-min periods; this procedure was repeated daily for four consecutive days. Several behavioural characteristics were recorded and the magnitude and direction of any changes in the characteristics with repeated exposure were analysed. Significant decreases over time were observed in the following characteristics: latency to the fist step, duration of freezing, sitting time, lying time, eye-closure and head-shaking, whereas significant increases with repeated testing were recorded for distress calling, number of steps taken, walking time, pecking, preening and jumping. No significant changes were observed in defaecation, standing time, bill opening or scratching the litter. The results are discussed in terms of the measurement of fearful behaviour under the assumption that experience in a novel environment may act to reduce the level of fear associated with that situation. INTRODUCTION
The present report describes a search for possible indices of fear in the domestic chick. One behavioural method of accomplishing such a search is to investigate adaptation or habituation to a novel environment or stimulus. Candland and Nagy (1969) made the point that “the assumption that unexperienced situations produced an increased state of emotion that dissipates with further experience in the situation leads to the further supposition that adaptation is a sign of the initial presence of heightened emotion&y”. It has been widely suggested that experience in a novel environment acts to reduce fear responses associated with the test situation and to increase other behaviours incompatible with fear reactions. Adaptation tests using a modified open field were therefore carried out to determine what, if any, changes occurred in several behavioural patterns with repeated testing and hence, presumably, increasing familiarity.
164
MATERIALS
AND METHODS
Animals used One-day-old chicks were housed in a brooder for 2 days before being installed in cardboard boxes measuring 68 X 38 X 30cm high. A bright emitter heater was suspended above each box; the floor of the box was covered with wood litter, and food and water were provided ad libitum. Chicks of three strains were used: a ‘flighty’ strain derived from Shaver 288 commercial hybrids (White Leghorn), a ‘docile’ strain derived from Thomber 909 commercial hybrids (Rhode Island Red and Light Sussex) and the J-line, a laboratory strain of Brown Leghorns. Ten males and ten females of each strain were used and were kept in the same-sex, same-strain groups of ten. The chicks remained undisturbed until testing at 6, 7, 8 and 9 days of age. A previous study performed in this laboratory (unpublished observation) revealed significant sex and strain differences in open field behaviour and, for this reason, both male and female chicks of the three stocks were used. Procedure The novel environment or open field consisted of a cardboard box identical to those in which the chicks were housed apart from the absence of food and water; a wire mesh lid prevented the birds from jumping out. A brightemitter heater was also suspended over the open field so that its ambient temperature was approximately the same as that of the home boxes. The present apparatus is a modified version of the classical open field described by Broadhurst (1960) with the main difference being the absence of white noise. Any aural stimuli occurring during testing were those of the normal background noise of the poultry house to which the chicks had been exposed since their first day of life. Each chick was tested individually; it was picked up gently, carried two m from its home box, and placed in the centre of the open field for a 15-min period. The characteristics recorded, by direct observation, were latency (to first step), freezing (duration), standing time, sitting time, time with eyes closed, lying time, walking time, steps taken, defaecation, distress calls, preens, pecks, head-shakes, wing flaps, jumps, bill openings and scratches at the litter. This procedure was repeated daily for four consecutive days so that each chick experienced four exposures to the open field; thus 240 tests were performed. The results were analysed using the analysis of variance. RESULTS
Table I displays the means and standard errors of the results obtained on the first and fourth days of testing for both sexes of the three strains used. Table II shows the magnitude and direction of the change in each behavioural
165
characteristic from day 1 to day 4, i.e. if y3c is the observation made on the xth day (x=1 to 4) then the magnitude of change = y4-yl. The grand mean significance values (end column) refer to the overall changes in all sexes and strains and were derived by the analysis of variance; any strain or sex deviation from the grand mean is indicated in the appropriate column. Minus values re fer to a decrease over time in that particular characteristic. Table III summarises the overall effect of repeated exposure to the open field upon each behavioural characteristic with respect to the direction of change. DISCUSSION
It has been proposed that inactivity following placement in a strange environment is a valid indicator of fearfulness in chickens (Candland and Nagy, 1969; Archer, 197315; Faure, 1975) and freezing and/or tonic immobility are thought to be prolonged by conditions designed to increase fear (Gallup et al., 1970) whereas fear reducers cause the reaction to wane (Gilman et al., 1950). It must be emphasised, however, that the latency to the first step is not synonymous with the latency to cease freezing. Both the latency to the first step (P < 0.05) and the duration of freezing (P < 0.01) show significant reductions with repeated testing in both males and females of all three strains. Thus, both of these characteristics may serve as useful indices of fear in the fowl under the assumption that fear responses dissipate with increasing familiarity. Hall (1934) defined emotional elimination as defaecation which ceased upon repeated exposure to the situation that originally evoked it, and several workers have since suggested a positive relationship between defaecation and fear. If such a relationship existed in the fowl, one would expect a decrease in defaecation with repeated testing. However, a recent study by Faure (1975) indicated that defaecation was inversely related to fear in chickens, though this effect disappeared after the first generation (personal communication, 1976). Conversely, the present study revealed no significant differences in defaecation from day to day in any of the groups and this casts doubt upon the validity of the defaecation measure as an index of fear in the chicken, at least in the strains observed. An alternative, though unlikely, explanation is that the level of fear originally evoked by the open field may not be high enough to allow differences in defaecation frequency with subsequent exposure to be revealed. However, defaecation has failed to correlate with other behavioural and physiological measures of fear in various species, and the dependence of this measure on the state of the gut immediately before testing renders it of a dubious nature. Several authors (Kaufman and Hinde, 1961; Sluckin et al., 1970) have referred to distress calling or the peep vocalization of the domestic chick as a fear response and Phillips and Siegel (1966) suggested that peeping represents a reflexive response that becomes conditioned to fear stimuli. Accordingly, distress calling would be expected to decrease with repeated testing.
time(s)
(no)
Head-shakes(
Pecks( no)
Preens(n0)
no)
Distress calls (no)
Defaecation
Steps (no)
Walking time(s)
Lying time(s)
Eyes closed(s)
Sitting time(s)
Standing
Freezing(s)
Latency(s)
36.6 14.2 90.5 15.7 217.9 38.3 0.8 0.1 518.5 53.7 0 0 3.5 2.6 4.5 0.9
17.7
66.3 13.8 45.1
16.9
18.8 6.3 6.4 3.1 700.2
0.6 7.1 2.7 1.9 0.3
772.3 42.3 2.9
0.2
0.6 0.8 0.3 0.7 0.3 211.0 12.5 502.3 29.2 0.7
684.8 12.2 2.5
0.7
1.0
1.2
5.6
34.4 11.7 10.0 3.5 635.2 47.7 143.3 42.9 50.9 6.9 57.8 9.1 53.8 6.8 129.5 16.6 0.5 0.2 404.7 39.0 0.5 0.2 4.4 1.8 4.7 0.9
Day 1
Day 1
Day 4
M
&2X
Thornber F
15.8 4.5 3.9 2.4 6.1 3.5 153.4 11.9 369.3 26.7 0.8 0.1 608.8 31.1 2.6 0.4 6.1 1.5 1.8 0.3
12.9
8.8 1.2 1.8 0.6 724.0
Day 4 12.8 2.6 12.6 4.5 684.1 10.5 27.6 8.1 7.6 2.7 10.4 3.9 168.5 13.0 389.1 25.9 0.7 0.2 638.5 4 7.6 0.1 0.1 0.7 0.3 3.6 0.6
Day 1
663.7 17.0 0 0 0 0 0 0 233.5 16.3 566.6 43.2 0.8 0.1 753.5 26.1 2.2 0.3 4.3 0.4 1.8 0.3
7.9 2.4 1.8 0.7
Day 4 9.3 1.5 2.0 0.8 707.8 12.2 1.6 1.6 0.3 0.3 1.3 0.9 185.3 13.1 442.4 31.1 0.7 0.2 697.4 33.6 1.6 0.4 3.1 0.5 2.9 0.6
14.9 2.7 10.2 2.9 684.6
0.7 0.2 4.8 1.2
41.9 0 0
32.4 12.1 111.0 13.2 266.2 30.5 0.8 0.2 545.5
10.5
63.2 12.6 26.9
12.9
Day 4
Day 1
M
chicks on the first and fourth
Shaver F
male and female
Strain
of 7-day-old
responses
I
Means of open-field errors (in italics)
TABLE
17.1 2.1 583.1 4 7.4 160.4 32.1 78.0 13.7 98.6 27.8 45.8 7.2 109.6 17.5 1.3 0.2 296.9 43.5 0.7 0.3 0.2 0.2 2.2 0.6
9.1
69.4
Day 1
J-line F
3.4 0.5 1.9 0.3
1.0
3.3 1.7 130.4 7. 7 303.5 17.2 1.3 0.2 475.9 40.1 4.0
1.9
35.7 6.4 8.2 2.9 733.1 12.1 25.0 6.4 5.6
78.4 8.4 26.7 3.5 543.6 50.8 208.0 39.0 102.9 28.1 85.5 24.1 36.2 5.9 83.8 14.3 0.7 0.2 328.2 54.0 0.5 0.3 0.9 0.4 2.5 0.7
Day 1
M
62.4 6.8 13.9 3.6 729.5 16.6 47.8 15.8 5.9 3.1 4.8 3.0 104.2 10.3 243.3 23.5 1.0 0. I 518.7 59.2 4.1 0.8 6.4 2.4 2.5 0.7
Day 4
with their standard
Day 4
days of testing,
& Q,
0.7 0.2 6.7 1.8 0.6 0.2 0 0
s = seconds; no = number.
Scratches (no)
Bill openings (no)
Jumps (no)
Wing flaps (no)
TABLE I (continued) 1.6 0.3 37.6 5.8 0.4 0.2 0 0
1.0 0.5 4.2 1.1 1.7 0.8 0 0
0.9 0.2 20.2 3.4 1.6 0.4 0 0
0.2 0.1 25.0 7.9 1.3 0.6 0.3 0.2
0.7 0.2 74.4 5.1 0.5 0.2 0 0
0 0 7.5 2.8 0.5 0.3 0 0
0.8 0.1 35.6 8.6 0.5 0.2 0 0
0.6 0.3 7.7 4.3 4.2 1.5 0 0
0.6 0.3 16.7 5.7 2.4 0.7 0.3 0.2
0.9 0.4 2.9 1.6 2.3 0.8 0 0
1.1
1.1 0.3 12.5 2.2 0.7 0.5 2.4
168
TABLE II The magnitude and direction of change from day 1 to day 4 in each parameter for males and females of the three strains and its significance value (analysis of variance) Parameters
Sex
J-line
Thornber
Latency
M F M F M F M F M F M F M F M F M F M F M F M F M F M F M F M F M F
-16.0 -33.7 0.3 0 -12.8 -8.9 190 179 190 194 186* 151* -160** -135** -97.0 -72.4 3.6 3.3 5.5 3.2 0.0 n.s. -0.3 n.s. 0.2 0.0 9.6 9.0 -1.6 -2.8 -80.7 -95.3 2.4 0.3 68.0 84.6
-25.6 -13.2 0.3 -0.1 -8.2 -5.4 204 254 240 284 89 -15 -127 -64 -47.0 -44.3 2.1 2.9 1.7 3.6 -2.9 -2.6 -0.1 0.9 16.0 30.9 -0.1 -0.2 -51.7 -35.9 0.0 0.0 99.6 120.5
Defaecation Freezing Distress calls Steps Standing Sitting Eyes closed Preening Pecking Head-shake Wing flap Jumping Bill open Lying Scratch Walking
Shaver -5.6 -4.9 -0.1 0.1 -8.0 -10.8 152 115 176 178 23 -20 -60 -27 -26.6* -7.6* 1.6 2.1 2.4 3.6 -1.9 -1.8 0.8 0.5 28.1 49.4 -0.0 -0.8 -31.1 -10.4 0.0 -0.3 74.3 65.0
* = p < 0.05; ** = P < 0.01; n.s. = not significant; M = male; F =
Grand mean values 0.05
n.s. 0.01 0.05 0.01 n.s. 0.05 0.01 0.01 0.05 0.05 n.s. 0.01 ns. 0.05 n.s. 0.01
female.
However, Faure (1975) defined an emotional or fearful bird as one which emitted few peeps, and Montevecchi et al. (1973) and Murphy (1976) found that distress calling was reduced by fear-provoking stimuli and that it increased with repeated test exposure. The present results support the latter findings in that distress calling showed significant overall increases (P < 0.05) over time in all groups; this suggests that if distress calling may indeed be used as an index of fear it should be in respect of an inverse relationship. The fact that this characteristic increased with repeated testing and hence,
169
TABLE III Effect of repeated exposure to the open field upon each behavioural parameter Decrease 1. Latency to first step 2. Duration of freezing
Increase
No change
1. Distress calling 2. Number of steps
3. Sitting time 4. Eye-closure
3. Preening 4. Pecking at walls and litter 5. Jumping
1. Defaecation 2. Standing time (except J-line) 3. Wing flapping 4. Bill open
5. Head-shaking (except J-line) 6. Lying time
5. Scratching at litter
6. Walking time
presumably, decreasing fear, suggests that distress calling may be a misnomer and that peeping may be a more suitable term. In line with previous observations (Guiton, 1959; Candland and Nagy, 1969) vocalization tended to be associated with alert upright posture, activity and ambulation although peeping also occurred at times when the chick was sitting. Repeated exposure of rats and mice to the open field often results in a gradual decrease in ambulation (Par?!, 1964; Nagy and Forest, 1970). However, low activity was found to be typical of a fearful bird in the open field (Faure, 1975) and Candland and Nagy (1969) discovered that activity increased with repeated testing in one-year-old White Leghorns. The present study also shows that repeated testing induced significant increases both in the number of steps taken (P < 0.01) and, correspondingly, in the time spent walking (P < 0.01). Hogan (1965) found that sitting and sleeping increased rapidly in Burmese Red Jungle Fowl chicks with increasing unfamiliarity and he consequently classified these behaviour patterns as fearful responses. Sleep was also classified as a fear response by Murphy (1976) when she demonstrated the induction of sleep by the presentation of a novel food source. The author feels that the index of sleep may be more valid if subdivided into time spent lying and time spent with the eyes closed. The present results demonstrated that the times spent sitting (P < 0.05), lying (P < 0.05) and/or with the eyes closed (P < 0.01) decreased significantly in all three strains from day to day and this suggests that these characteristics may indeed be useful as positive indices of fear. The time spent standing showed a significant (P < 0.05) increase with repeated testing in J-line males and females but no change in either Thombers or Shavers. The J-line trend may simply occur as a reciprocal of the marked reduction from the very high initial levels of sitting and lying exhibited by this strain. The frequency of preening increased significantly (P < 0.01) with repeated testing in all groups. This was not the hurried, incomplete preening commonly released in extreme conflict situations (Duncan and Wood-Gush, 1972)
170
but may still be a displacement activity, i.e. the level of fear evoked on initial placement in the open field may exclude any other behaviour but, as fearfulness decreases with repeated exposure, previously incompatible behaviours may emerge and conflict with fear. Bolles (1960) and Woods (1962) found increased grooming in rats over successive periods in a novel situation, and Coover et al. (1973) proposed that self-grooming suggested a state of relaxation in the rat. A similar mechanism may operate in the chick, preening increasing with decreasing levels of fear. This suggestion gains support from the work of Hogan and Abel (1971) who found that handling increased preening; handling is commonly assumed to reduce fear in subsequent fearevoking situations. It has been suggested that pecking at the environment indicates an absence of fear, at least in adult fowl (Hughes and Duncan, 1972; Hughes and Black, 1974). The significant (P < 0.015) increase in pecking rates with repeated exposure in the present study suggests that the use of this characteristic as an index of fear can be extended to include the chick. Recent observations on head-shaking in adult Shavers (Hughes and Black, 1974) disclosed a slight increase under confined conditions in the same direction as ‘fear’. There was no significant difference in head-shaking frequency over time in J-line chicks but Thombers and Shavers showed significant (P < 0.05) reductions from day to day. Thus, in certain strains and under certain conditions, head-shaking might be regarded as a positive fear response. Strong evidence that head-shaking occurs in conflict situations (Hogan, 1965) lends indirect support to the above suggestion. Jumping scores have been used as measures of fearful behaviour by Archer (1973b) who found a decline in jumping in a novel environment over six testing days in male Warren sex-linked chicks; this suggests a positive relationship with fear. Conversely, Faure (1975) and Murphy (1976), using Comish, and Shaver and Thomber chicks respectively, proposed that the occurrence of jumping indicated low levels of fear. The present study showed a marked and significant (P < 0.01) increase in jumping with repeated exposure, which suggests an inverse relationship with fear. The difference between these results and those of Archer (197313) may be due to strain and/or procedural differences. Archer’s chicks were individually housed whereas mine were group-housed, so the group-housed chicks had to contend not only with placement in a strange environment but also with separation from their brood mates. Thus, the increasing levels of activity, peeping and jumping over time may reflect the gradually increasing predominance of active search and escape patterns in an attempt to regain contact with the brood mates, with a concurrent reduction of sitting and ‘sleeping’. Archer’s chicks were tested at 3,4, 5,10, 11 and 12 days of age whereas those used in the present study were observed when 6, 7, 8 and 9 days old. Another difference is that Archer’s chicks were subjected to intramuscular injection of androgen or oil vehicle at 2 days of age whereas mine received no such treatment. Another possibility is that the jumping scores may reflect avoidance of the test situation
171
without the involvement of fear; however, no clear cut conclusions can be drawn from the present results. No significant differences in the frequencies of wing flapping, bill opening or scratching at the litter were found with repeated testing, and so the use of these behaviour patterns as indices of fear in chicks of these ages and strains is questionable. The concepts of exploration and fear/emotionality have been regarded either as independent of one another (Whimbey and Denenberg, 1967) or as being closely related (Lester, 1968) but the common assumption is that fear and exploration are inversely related. Ambulation in a novel environment has been used not only as an inverse measure of fear but also to denote exploration; this assumption, however, omits a number of alternative categories of exploratory behaviour. Pecking has been described as a typical exploratory response in the chicken (Wunschman, 1963; Home and Wood-Gush, 1970) and the fact that the changes over time in this trait closely parallel those in ambulation lends some support to the above inverse relationship hypothesis. Further support comes from the inverse relationship between ambulation+pecking and characteristics such as freezing, sitting, eye-closure, etc., which may be regarded as fear responses. For a detailed account of the fear and exploration controversy, at least in rodents, the reader is referred to a review by Archer (1973a). The suggestion that the changes observed in the measures used in the present study are due to a reduction in fear could be countered by the argument that they are the result of maturational effects. However, it seems difficult to understand why some of the changes observed, e.g. eye-closure, head-shaking, should be affected by maturation. It has been shown that distress calling in the chicken decreases from 1 to 15 days of age (Candland and Nagy, 1969) whereas significant increases were found in the frequency of this behaviour in the present study with repeated testing and, hence, increasing age. It has also been found that the duration of eye-closure increases with age (Rovee and Kleinman, 1974) whereas this behaviour decreased in the present study. The strong, albeit indirect, evidence presented for the relationships of the behaviour patterns recorded to fear provide further support for the fear-reduction hypothesis. The sex and strain differences previously observed (unpublished observation) are again apparent in the present study, with greater activity shown by females than by males and by Thombers and Shavers than by J-line chicks. These findings may reflect sex and strain differences in fearfulness or in the reactions to fear-elicitation. The ‘docile’ Thombers might have been expected to be less fearful in the open field than the ‘flighty’ Shaver strain but the somewhat lower activity and greater sitting/lying times shown by Thombers upon initial placement in the open field argues against such a suggestion. The classification of a strain as docile suggests low fearfulness but may, in fact, simply reflect the inhibitory effect of fear on activity. In view of the above differences, care must be taken in generalising from
172
the present results to other strains and species and the importance the sex of the subjects used is emphasized.
of stating
ACKNOWLEDGEMENTS
I would like to thank Dr D.G.M. Wood-Gush for his constructive criticism of the present manuscript. I am also grateful to Mrs Caroline McCorquodale for her valuable assistance with the statistical analysis. REFERENCES Archer, J., 1973a. Tests for emotionality in rats and mice; a review. Anim. Behav., 21: 205-235. Archer, J., 1973b. The influence of testosterone on chick behaviour in novel environments. Behav. Biol., 8: 93-108. Bolles, R.C., 1960. Grooming behavior in the rat. J. Comp. Physiol. Psychol., 53: 306310. Broadhurst, P.L., 1960. Experiments in psychogenetics: applications of biometrical genetics to the inheritance of behaviour. In: H.J. Eysenck (Editor), Experiments in Personality. Vol. 1. Psychogenetics and Psychopharmacology. Routledge andKegan Paul, London, pp. l-102. Candland, D.K. and Nagy, Z.M., 1969. The open field: some comparative data. Ann. N.Y. Acad. Sci., 159: 831-851. Coover, G.D., Ursin, H. and Levine, S., 1973. Plasma-corticosterone levels during active avoidance learning in rats. J. Comp. Physiol. Psychol., 82: 170-174. Duncan, I.J.H. and Wood-Gush, D.G.M., 1972. An analysis of displacement preening in the domestic fowl. Anim. Behav., 20: 68-71. Faure, J.M., 1975. Etude des liaisons entre comportement en open-field et Bmotivite chez le jeune poussin. Ann. G&r&. SBl. Anim., 7: 197-204. Gallup, G.G.Jr., Nash, R.F., Potter, R.J. and Donegan, N.H., 1970. Effect of varying conditions of fear on immobility reactions in domestic chickens (Gallus gallus). J. Comp. Physiol. Psychol., 73: 442-445. Gilman, T.T., Marcuse, F.L. and Moore, A.U., 1950. Animal hypnosis: a study of the induction of tonic immobility in chickens. J. Comp. Physiol. Psychol., 43: 99-111. Guiton, P., 1959. Socialization and imprinting in Brown Leghorn chicks. Anim. Behav., 7: 26-34, Hall, C.S., 1934. Emotional behavior in the rat. 1. Defaecation and urination as measures of individual differences in emotionality. J. Comp. Psychol., 18: 385-403. Hogan, J.A., 1965. An experimental study of conflict and fear: an analysis of behaviour of young chicks towards a mealworm. Part 1. The behaviour of chicks which do not eat the mealworm. Behaviour, 25/26: 45-95. Hogan, J.A. and Abel, E.L., 1971. Effects of social factors on response to unfamiliar environments in Gallus gallus spadiceus. Anim. Behav., 19: 687-694. Horne, A.R. and Wood-Gush, D.G.M., 1970. Exploratory activity following oestrogen treatment in ovariectomized Brown Leghorn females. Rev. Comportement Anim., 4: 46-50. Hughes, B.O. and Black, A.J., 1974. The effect of environmental factors on activity, selected behaviour patterns and “fear” of fowls in cages and pens. Br. Poult. Sci., 15: 375-380. Hughes, B.O. and Duncan, I.J.H., 1972. The influence of strain and environmental factors upon feather pecking and cannibalism in fowls. Br. Poult. Sci., 13: 525-547. Kaufman, I.C. and Hinde, R.A., 1961. Factors influencing distress calling in chicks with special reference to temperature and social isolation. Anim. Behav., 9: 197-204.
Lester, D., 1968. Two tests of a fear-motivated theory of exploration. Psychon. Sci., 10: 385-386. Montevecchi, W.A., Gallup, G.G. Jr. and Dunlap, W.P., 1973. The peep vocalization in group reared chicks (Gallus domesticus): its relation to fear. Anim. Behav., 21: 116-123. Murphy, L.B., 1976. A study of the bebavioural expression of fear and exploration in two stocks of domestic fowl. Ph.D. Thesis, Univ. Edinburgh, 342 pp. Nagy, Z.M. and Forest, E.J., 1970. Open field behavior of C3H mice: effect of size and illumination of field. Psychon. Sci., 20: 19-21. Pars, W.P., 1964. Relationship of various behaviors in the open field test of emotionality. Psychol. Rep., 14: 19-22. Phillips, R.E. and Siegel, P.B., 1966. Development of fear in chicks of two closely related genetic lines. Anim. Behav., 14: 84-88. Rovee, C.K. and Kleinman, J.M., 1974. Developmental changes in tonic immobility in young chicks (Gallus gallus). Dev. Psychobiol., 7: 71-77. Sluckin, W., Fullerton, C. and Guiton, P., 1970. The development of aversive responses in domestic chicks. Rev. Comportement Anim., 4: 73-79. Whimbey, A.E. and Denenberg, V.H., 1967. Two independent behavioral dimensions in open field performance. J. Comp. Physiol., Psychol., 63: 500-504. Woods, P.J., 1962. Behavior in a novel situation as influenced by the immediately preceding environment. J. Exp. Anal. Behav., 5: 185-190. Wunschman, A., 1963. Quantitative Untersuchungen zum Neugierverhalten von Wirbeltieren. Z. Tierpsychol., 20: 80-109.
REPEATED EXPOSURE OF THE DOMESTIC CHICK TO A NOVEL ENVIRONMENT: EFFECTS ON BEHAVIOURAL RESPONSES
R.B. JONES Agricultural Research Council’s Poultry Research Road, Edinburgh EH9 3JS (Great Britain)
Centre, King’s Buildings,
West Mains
(Received 19 January 1977)
ABSTRACT Jones, R.B., 1977. Repeated exposure of the domestic chick to a novel environment: effects on behavioural responses. Behav. Processes, 2: 163-173. Seven-day-old male and female chicks of three strains were placed individually in an open field or novel environment for 15-min periods; this procedure was repeated daily for four consecutive days. Several behavioural characteristics were recorded and the magnitude and direction of any changes in the characteristics with repeated exposure were analysed. Significant decreases over time were observed in the following characteristics: latency to the fist step, duration of freezing, sitting time, lying time, eye-closure and head-shaking, whereas significant increases with repeated testing were recorded for distress calling, number of steps taken, walking time, pecking, preening and jumping. No significant changes were observed in defaecation, standing time, bill opening or scratching the litter. The results are discussed in terms of the measurement of fearful behaviour under the assumption that experience in a novel environment may act to reduce the level of fear associated with that situation. INTRODUCTION
The present report describes a search for possible indices of fear in the domestic chick. One behavioural method of accomplishing such a search is to investigate adaptation or habituation to a novel environment or stimulus. Candland and Nagy (1969) made the point that “the assumption that unexperienced situations produced an increased state of emotion that dissipates with further experience in the situation leads to the further supposition that adaptation is a sign of the initial presence of heightened emotion&y”. It has been widely suggested that experience in a novel environment acts to reduce fear responses associated with the test situation and to increase other behaviours incompatible with fear reactions. Adaptation tests using a modified open field were therefore carried out to determine what, if any, changes occurred in several behavioural patterns with repeated testing and hence, presumably, increasing familiarity.
164
MATERIALS
AND METHODS
Animals used One-day-old chicks were housed in a brooder for 2 days before being installed in cardboard boxes measuring 68 X 38 X 30cm high. A bright emitter heater was suspended above each box; the floor of the box was covered with wood litter, and food and water were provided ad libitum. Chicks of three strains were used: a ‘flighty’ strain derived from Shaver 288 commercial hybrids (White Leghorn), a ‘docile’ strain derived from Thomber 909 commercial hybrids (Rhode Island Red and Light Sussex) and the J-line, a laboratory strain of Brown Leghorns. Ten males and ten females of each strain were used and were kept in the same-sex, same-strain groups of ten. The chicks remained undisturbed until testing at 6, 7, 8 and 9 days of age. A previous study performed in this laboratory (unpublished observation) revealed significant sex and strain differences in open field behaviour and, for this reason, both male and female chicks of the three stocks were used. Procedure The novel environment or open field consisted of a cardboard box identical to those in which the chicks were housed apart from the absence of food and water; a wire mesh lid prevented the birds from jumping out. A brightemitter heater was also suspended over the open field so that its ambient temperature was approximately the same as that of the home boxes. The present apparatus is a modified version of the classical open field described by Broadhurst (1960) with the main difference being the absence of white noise. Any aural stimuli occurring during testing were those of the normal background noise of the poultry house to which the chicks had been exposed since their first day of life. Each chick was tested individually; it was picked up gently, carried two m from its home box, and placed in the centre of the open field for a 15-min period. The characteristics recorded, by direct observation, were latency (to first step), freezing (duration), standing time, sitting time, time with eyes closed, lying time, walking time, steps taken, defaecation, distress calls, preens, pecks, head-shakes, wing flaps, jumps, bill openings and scratches at the litter. This procedure was repeated daily for four consecutive days so that each chick experienced four exposures to the open field; thus 240 tests were performed. The results were analysed using the analysis of variance. RESULTS
Table I displays the means and standard errors of the results obtained on the first and fourth days of testing for both sexes of the three strains used. Table II shows the magnitude and direction of the change in each behavioural
165
characteristic from day 1 to day 4, i.e. if y3c is the observation made on the xth day (x=1 to 4) then the magnitude of change = y4-yl. The grand mean significance values (end column) refer to the overall changes in all sexes and strains and were derived by the analysis of variance; any strain or sex deviation from the grand mean is indicated in the appropriate column. Minus values re fer to a decrease over time in that particular characteristic. Table III summarises the overall effect of repeated exposure to the open field upon each behavioural characteristic with respect to the direction of change. DISCUSSION
It has been proposed that inactivity following placement in a strange environment is a valid indicator of fearfulness in chickens (Candland and Nagy, 1969; Archer, 197315; Faure, 1975) and freezing and/or tonic immobility are thought to be prolonged by conditions designed to increase fear (Gallup et al., 1970) whereas fear reducers cause the reaction to wane (Gilman et al., 1950). It must be emphasised, however, that the latency to the first step is not synonymous with the latency to cease freezing. Both the latency to the first step (P < 0.05) and the duration of freezing (P < 0.01) show significant reductions with repeated testing in both males and females of all three strains. Thus, both of these characteristics may serve as useful indices of fear in the fowl under the assumption that fear responses dissipate with increasing familiarity. Hall (1934) defined emotional elimination as defaecation which ceased upon repeated exposure to the situation that originally evoked it, and several workers have since suggested a positive relationship between defaecation and fear. If such a relationship existed in the fowl, one would expect a decrease in defaecation with repeated testing. However, a recent study by Faure (1975) indicated that defaecation was inversely related to fear in chickens, though this effect disappeared after the first generation (personal communication, 1976). Conversely, the present study revealed no significant differences in defaecation from day to day in any of the groups and this casts doubt upon the validity of the defaecation measure as an index of fear in the chicken, at least in the strains observed. An alternative, though unlikely, explanation is that the level of fear originally evoked by the open field may not be high enough to allow differences in defaecation frequency with subsequent exposure to be revealed. However, defaecation has failed to correlate with other behavioural and physiological measures of fear in various species, and the dependence of this measure on the state of the gut immediately before testing renders it of a dubious nature. Several authors (Kaufman and Hinde, 1961; Sluckin et al., 1970) have referred to distress calling or the peep vocalization of the domestic chick as a fear response and Phillips and Siegel (1966) suggested that peeping represents a reflexive response that becomes conditioned to fear stimuli. Accordingly, distress calling would be expected to decrease with repeated testing.
time(s)
(no)
Head-shakes(
Pecks( no)
Preens(n0)
no)
Distress calls (no)
Defaecation
Steps (no)
Walking time(s)
Lying time(s)
Eyes closed(s)
Sitting time(s)
Standing
Freezing(s)
Latency(s)
36.6 14.2 90.5 15.7 217.9 38.3 0.8 0.1 518.5 53.7 0 0 3.5 2.6 4.5 0.9
17.7
66.3 13.8 45.1
16.9
18.8 6.3 6.4 3.1 700.2
0.6 7.1 2.7 1.9 0.3
772.3 42.3 2.9
0.2
0.6 0.8 0.3 0.7 0.3 211.0 12.5 502.3 29.2 0.7
684.8 12.2 2.5
0.7
1.0
1.2
5.6
34.4 11.7 10.0 3.5 635.2 47.7 143.3 42.9 50.9 6.9 57.8 9.1 53.8 6.8 129.5 16.6 0.5 0.2 404.7 39.0 0.5 0.2 4.4 1.8 4.7 0.9
Day 1
Day 1
Day 4
M
&2X
Thornber F
15.8 4.5 3.9 2.4 6.1 3.5 153.4 11.9 369.3 26.7 0.8 0.1 608.8 31.1 2.6 0.4 6.1 1.5 1.8 0.3
12.9
8.8 1.2 1.8 0.6 724.0
Day 4 12.8 2.6 12.6 4.5 684.1 10.5 27.6 8.1 7.6 2.7 10.4 3.9 168.5 13.0 389.1 25.9 0.7 0.2 638.5 4 7.6 0.1 0.1 0.7 0.3 3.6 0.6
Day 1
663.7 17.0 0 0 0 0 0 0 233.5 16.3 566.6 43.2 0.8 0.1 753.5 26.1 2.2 0.3 4.3 0.4 1.8 0.3
7.9 2.4 1.8 0.7
Day 4 9.3 1.5 2.0 0.8 707.8 12.2 1.6 1.6 0.3 0.3 1.3 0.9 185.3 13.1 442.4 31.1 0.7 0.2 697.4 33.6 1.6 0.4 3.1 0.5 2.9 0.6
14.9 2.7 10.2 2.9 684.6
0.7 0.2 4.8 1.2
41.9 0 0
32.4 12.1 111.0 13.2 266.2 30.5 0.8 0.2 545.5
10.5
63.2 12.6 26.9
12.9
Day 4
Day 1
M
chicks on the first and fourth
Shaver F
male and female
Strain
of 7-day-old
responses
I
Means of open-field errors (in italics)
TABLE
17.1 2.1 583.1 4 7.4 160.4 32.1 78.0 13.7 98.6 27.8 45.8 7.2 109.6 17.5 1.3 0.2 296.9 43.5 0.7 0.3 0.2 0.2 2.2 0.6
9.1
69.4
Day 1
J-line F
3.4 0.5 1.9 0.3
1.0
3.3 1.7 130.4 7. 7 303.5 17.2 1.3 0.2 475.9 40.1 4.0
1.9
35.7 6.4 8.2 2.9 733.1 12.1 25.0 6.4 5.6
78.4 8.4 26.7 3.5 543.6 50.8 208.0 39.0 102.9 28.1 85.5 24.1 36.2 5.9 83.8 14.3 0.7 0.2 328.2 54.0 0.5 0.3 0.9 0.4 2.5 0.7
Day 1
M
62.4 6.8 13.9 3.6 729.5 16.6 47.8 15.8 5.9 3.1 4.8 3.0 104.2 10.3 243.3 23.5 1.0 0. I 518.7 59.2 4.1 0.8 6.4 2.4 2.5 0.7
Day 4
with their standard
Day 4
days of testing,
& Q,
0.7 0.2 6.7 1.8 0.6 0.2 0 0
s = seconds; no = number.
Scratches (no)
Bill openings (no)
Jumps (no)
Wing flaps (no)
TABLE I (continued) 1.6 0.3 37.6 5.8 0.4 0.2 0 0
1.0 0.5 4.2 1.1 1.7 0.8 0 0
0.9 0.2 20.2 3.4 1.6 0.4 0 0
0.2 0.1 25.0 7.9 1.3 0.6 0.3 0.2
0.7 0.2 74.4 5.1 0.5 0.2 0 0
0 0 7.5 2.8 0.5 0.3 0 0
0.8 0.1 35.6 8.6 0.5 0.2 0 0
0.6 0.3 7.7 4.3 4.2 1.5 0 0
0.6 0.3 16.7 5.7 2.4 0.7 0.3 0.2
0.9 0.4 2.9 1.6 2.3 0.8 0 0
1.1
1.1 0.3 12.5 2.2 0.7 0.5 2.4
168
TABLE II The magnitude and direction of change from day 1 to day 4 in each parameter for males and females of the three strains and its significance value (analysis of variance) Parameters
Sex
J-line
Thornber
Latency
M F M F M F M F M F M F M F M F M F M F M F M F M F M F M F M F M F
-16.0 -33.7 0.3 0 -12.8 -8.9 190 179 190 194 186* 151* -160** -135** -97.0 -72.4 3.6 3.3 5.5 3.2 0.0 n.s. -0.3 n.s. 0.2 0.0 9.6 9.0 -1.6 -2.8 -80.7 -95.3 2.4 0.3 68.0 84.6
-25.6 -13.2 0.3 -0.1 -8.2 -5.4 204 254 240 284 89 -15 -127 -64 -47.0 -44.3 2.1 2.9 1.7 3.6 -2.9 -2.6 -0.1 0.9 16.0 30.9 -0.1 -0.2 -51.7 -35.9 0.0 0.0 99.6 120.5
Defaecation Freezing Distress calls Steps Standing Sitting Eyes closed Preening Pecking Head-shake Wing flap Jumping Bill open Lying Scratch Walking
Shaver -5.6 -4.9 -0.1 0.1 -8.0 -10.8 152 115 176 178 23 -20 -60 -27 -26.6* -7.6* 1.6 2.1 2.4 3.6 -1.9 -1.8 0.8 0.5 28.1 49.4 -0.0 -0.8 -31.1 -10.4 0.0 -0.3 74.3 65.0
* = p < 0.05; ** = P < 0.01; n.s. = not significant; M = male; F =
Grand mean values 0.05
n.s. 0.01 0.05 0.01 n.s. 0.05 0.01 0.01 0.05 0.05 n.s. 0.01 ns. 0.05 n.s. 0.01
female.
However, Faure (1975) defined an emotional or fearful bird as one which emitted few peeps, and Montevecchi et al. (1973) and Murphy (1976) found that distress calling was reduced by fear-provoking stimuli and that it increased with repeated test exposure. The present results support the latter findings in that distress calling showed significant overall increases (P < 0.05) over time in all groups; this suggests that if distress calling may indeed be used as an index of fear it should be in respect of an inverse relationship. The fact that this characteristic increased with repeated testing and hence,
169
TABLE III Effect of repeated exposure to the open field upon each behavioural parameter Decrease 1. Latency to first step 2. Duration of freezing
Increase
No change
1. Distress calling 2. Number of steps
3. Sitting time 4. Eye-closure
3. Preening 4. Pecking at walls and litter 5. Jumping
1. Defaecation 2. Standing time (except J-line) 3. Wing flapping 4. Bill open
5. Head-shaking (except J-line) 6. Lying time
5. Scratching at litter
6. Walking time
presumably, decreasing fear, suggests that distress calling may be a misnomer and that peeping may be a more suitable term. In line with previous observations (Guiton, 1959; Candland and Nagy, 1969) vocalization tended to be associated with alert upright posture, activity and ambulation although peeping also occurred at times when the chick was sitting. Repeated exposure of rats and mice to the open field often results in a gradual decrease in ambulation (Par?!, 1964; Nagy and Forest, 1970). However, low activity was found to be typical of a fearful bird in the open field (Faure, 1975) and Candland and Nagy (1969) discovered that activity increased with repeated testing in one-year-old White Leghorns. The present study also shows that repeated testing induced significant increases both in the number of steps taken (P < 0.01) and, correspondingly, in the time spent walking (P < 0.01). Hogan (1965) found that sitting and sleeping increased rapidly in Burmese Red Jungle Fowl chicks with increasing unfamiliarity and he consequently classified these behaviour patterns as fearful responses. Sleep was also classified as a fear response by Murphy (1976) when she demonstrated the induction of sleep by the presentation of a novel food source. The author feels that the index of sleep may be more valid if subdivided into time spent lying and time spent with the eyes closed. The present results demonstrated that the times spent sitting (P < 0.05), lying (P < 0.05) and/or with the eyes closed (P < 0.01) decreased significantly in all three strains from day to day and this suggests that these characteristics may indeed be useful as positive indices of fear. The time spent standing showed a significant (P < 0.05) increase with repeated testing in J-line males and females but no change in either Thombers or Shavers. The J-line trend may simply occur as a reciprocal of the marked reduction from the very high initial levels of sitting and lying exhibited by this strain. The frequency of preening increased significantly (P < 0.01) with repeated testing in all groups. This was not the hurried, incomplete preening commonly released in extreme conflict situations (Duncan and Wood-Gush, 1972)
170
but may still be a displacement activity, i.e. the level of fear evoked on initial placement in the open field may exclude any other behaviour but, as fearfulness decreases with repeated exposure, previously incompatible behaviours may emerge and conflict with fear. Bolles (1960) and Woods (1962) found increased grooming in rats over successive periods in a novel situation, and Coover et al. (1973) proposed that self-grooming suggested a state of relaxation in the rat. A similar mechanism may operate in the chick, preening increasing with decreasing levels of fear. This suggestion gains support from the work of Hogan and Abel (1971) who found that handling increased preening; handling is commonly assumed to reduce fear in subsequent fearevoking situations. It has been suggested that pecking at the environment indicates an absence of fear, at least in adult fowl (Hughes and Duncan, 1972; Hughes and Black, 1974). The significant (P < 0.015) increase in pecking rates with repeated exposure in the present study suggests that the use of this characteristic as an index of fear can be extended to include the chick. Recent observations on head-shaking in adult Shavers (Hughes and Black, 1974) disclosed a slight increase under confined conditions in the same direction as ‘fear’. There was no significant difference in head-shaking frequency over time in J-line chicks but Thombers and Shavers showed significant (P < 0.05) reductions from day to day. Thus, in certain strains and under certain conditions, head-shaking might be regarded as a positive fear response. Strong evidence that head-shaking occurs in conflict situations (Hogan, 1965) lends indirect support to the above suggestion. Jumping scores have been used as measures of fearful behaviour by Archer (1973b) who found a decline in jumping in a novel environment over six testing days in male Warren sex-linked chicks; this suggests a positive relationship with fear. Conversely, Faure (1975) and Murphy (1976), using Comish, and Shaver and Thomber chicks respectively, proposed that the occurrence of jumping indicated low levels of fear. The present study showed a marked and significant (P < 0.01) increase in jumping with repeated exposure, which suggests an inverse relationship with fear. The difference between these results and those of Archer (197313) may be due to strain and/or procedural differences. Archer’s chicks were individually housed whereas mine were group-housed, so the group-housed chicks had to contend not only with placement in a strange environment but also with separation from their brood mates. Thus, the increasing levels of activity, peeping and jumping over time may reflect the gradually increasing predominance of active search and escape patterns in an attempt to regain contact with the brood mates, with a concurrent reduction of sitting and ‘sleeping’. Archer’s chicks were tested at 3,4, 5,10, 11 and 12 days of age whereas those used in the present study were observed when 6, 7, 8 and 9 days old. Another difference is that Archer’s chicks were subjected to intramuscular injection of androgen or oil vehicle at 2 days of age whereas mine received no such treatment. Another possibility is that the jumping scores may reflect avoidance of the test situation
171
without the involvement of fear; however, no clear cut conclusions can be drawn from the present results. No significant differences in the frequencies of wing flapping, bill opening or scratching at the litter were found with repeated testing, and so the use of these behaviour patterns as indices of fear in chicks of these ages and strains is questionable. The concepts of exploration and fear/emotionality have been regarded either as independent of one another (Whimbey and Denenberg, 1967) or as being closely related (Lester, 1968) but the common assumption is that fear and exploration are inversely related. Ambulation in a novel environment has been used not only as an inverse measure of fear but also to denote exploration; this assumption, however, omits a number of alternative categories of exploratory behaviour. Pecking has been described as a typical exploratory response in the chicken (Wunschman, 1963; Home and Wood-Gush, 1970) and the fact that the changes over time in this trait closely parallel those in ambulation lends some support to the above inverse relationship hypothesis. Further support comes from the inverse relationship between ambulation+pecking and characteristics such as freezing, sitting, eye-closure, etc., which may be regarded as fear responses. For a detailed account of the fear and exploration controversy, at least in rodents, the reader is referred to a review by Archer (1973a). The suggestion that the changes observed in the measures used in the present study are due to a reduction in fear could be countered by the argument that they are the result of maturational effects. However, it seems difficult to understand why some of the changes observed, e.g. eye-closure, head-shaking, should be affected by maturation. It has been shown that distress calling in the chicken decreases from 1 to 15 days of age (Candland and Nagy, 1969) whereas significant increases were found in the frequency of this behaviour in the present study with repeated testing and, hence, increasing age. It has also been found that the duration of eye-closure increases with age (Rovee and Kleinman, 1974) whereas this behaviour decreased in the present study. The strong, albeit indirect, evidence presented for the relationships of the behaviour patterns recorded to fear provide further support for the fear-reduction hypothesis. The sex and strain differences previously observed (unpublished observation) are again apparent in the present study, with greater activity shown by females than by males and by Thombers and Shavers than by J-line chicks. These findings may reflect sex and strain differences in fearfulness or in the reactions to fear-elicitation. The ‘docile’ Thombers might have been expected to be less fearful in the open field than the ‘flighty’ Shaver strain but the somewhat lower activity and greater sitting/lying times shown by Thombers upon initial placement in the open field argues against such a suggestion. The classification of a strain as docile suggests low fearfulness but may, in fact, simply reflect the inhibitory effect of fear on activity. In view of the above differences, care must be taken in generalising from
172
the present results to other strains and species and the importance the sex of the subjects used is emphasized.
of stating
ACKNOWLEDGEMENTS
I would like to thank Dr D.G.M. Wood-Gush for his constructive criticism of the present manuscript. I am also grateful to Mrs Caroline McCorquodale for her valuable assistance with the statistical analysis. REFERENCES Archer, J., 1973a. Tests for emotionality in rats and mice; a review. Anim. Behav., 21: 205-235. Archer, J., 1973b. The influence of testosterone on chick behaviour in novel environments. Behav. Biol., 8: 93-108. Bolles, R.C., 1960. Grooming behavior in the rat. J. Comp. Physiol. Psychol., 53: 306310. Broadhurst, P.L., 1960. Experiments in psychogenetics: applications of biometrical genetics to the inheritance of behaviour. In: H.J. Eysenck (Editor), Experiments in Personality. Vol. 1. Psychogenetics and Psychopharmacology. Routledge andKegan Paul, London, pp. l-102. Candland, D.K. and Nagy, Z.M., 1969. The open field: some comparative data. Ann. N.Y. Acad. Sci., 159: 831-851. Coover, G.D., Ursin, H. and Levine, S., 1973. Plasma-corticosterone levels during active avoidance learning in rats. J. Comp. Physiol. Psychol., 82: 170-174. Duncan, I.J.H. and Wood-Gush, D.G.M., 1972. An analysis of displacement preening in the domestic fowl. Anim. Behav., 20: 68-71. Faure, J.M., 1975. Etude des liaisons entre comportement en open-field et Bmotivite chez le jeune poussin. Ann. G&r&. SBl. Anim., 7: 197-204. Gallup, G.G.Jr., Nash, R.F., Potter, R.J. and Donegan, N.H., 1970. Effect of varying conditions of fear on immobility reactions in domestic chickens (Gallus gallus). J. Comp. Physiol. Psychol., 73: 442-445. Gilman, T.T., Marcuse, F.L. and Moore, A.U., 1950. Animal hypnosis: a study of the induction of tonic immobility in chickens. J. Comp. Physiol. Psychol., 43: 99-111. Guiton, P., 1959. Socialization and imprinting in Brown Leghorn chicks. Anim. Behav., 7: 26-34, Hall, C.S., 1934. Emotional behavior in the rat. 1. Defaecation and urination as measures of individual differences in emotionality. J. Comp. Psychol., 18: 385-403. Hogan, J.A., 1965. An experimental study of conflict and fear: an analysis of behaviour of young chicks towards a mealworm. Part 1. The behaviour of chicks which do not eat the mealworm. Behaviour, 25/26: 45-95. Hogan, J.A. and Abel, E.L., 1971. Effects of social factors on response to unfamiliar environments in Gallus gallus spadiceus. Anim. Behav., 19: 687-694. Horne, A.R. and Wood-Gush, D.G.M., 1970. Exploratory activity following oestrogen treatment in ovariectomized Brown Leghorn females. Rev. Comportement Anim., 4: 46-50. Hughes, B.O. and Black, A.J., 1974. The effect of environmental factors on activity, selected behaviour patterns and “fear” of fowls in cages and pens. Br. Poult. Sci., 15: 375-380. Hughes, B.O. and Duncan, I.J.H., 1972. The influence of strain and environmental factors upon feather pecking and cannibalism in fowls. Br. Poult. Sci., 13: 525-547. Kaufman, I.C. and Hinde, R.A., 1961. Factors influencing distress calling in chicks with special reference to temperature and social isolation. Anim. Behav., 9: 197-204.
Lester, D., 1968. Two tests of a fear-motivated theory of exploration. Psychon. Sci., 10: 385-386. Montevecchi, W.A., Gallup, G.G. Jr. and Dunlap, W.P., 1973. The peep vocalization in group reared chicks (Gallus domesticus): its relation to fear. Anim. Behav., 21: 116-123. Murphy, L.B., 1976. A study of the bebavioural expression of fear and exploration in two stocks of domestic fowl. Ph.D. Thesis, Univ. Edinburgh, 342 pp. Nagy, Z.M. and Forest, E.J., 1970. Open field behavior of C3H mice: effect of size and illumination of field. Psychon. Sci., 20: 19-21. Pars, W.P., 1964. Relationship of various behaviors in the open field test of emotionality. Psychol. Rep., 14: 19-22. Phillips, R.E. and Siegel, P.B., 1966. Development of fear in chicks of two closely related genetic lines. Anim. Behav., 14: 84-88. Rovee, C.K. and Kleinman, J.M., 1974. Developmental changes in tonic immobility in young chicks (Gallus gallus). Dev. Psychobiol., 7: 71-77. Sluckin, W., Fullerton, C. and Guiton, P., 1970. The development of aversive responses in domestic chicks. Rev. Comportement Anim., 4: 73-79. Whimbey, A.E. and Denenberg, V.H., 1967. Two independent behavioral dimensions in open field performance. J. Comp. Physiol., Psychol., 63: 500-504. Woods, P.J., 1962. Behavior in a novel situation as influenced by the immediately preceding environment. J. Exp. Anal. Behav., 5: 185-190. Wunschman, A., 1963. Quantitative Untersuchungen zum Neugierverhalten von Wirbeltieren. Z. Tierpsychol., 20: 80-109.