Behavioural Processes 38 (1996) 193-202

Temporal structure of red jungle fowl crow sequences: single-case analysis ’

P. Koene

Department of Animal Husbandry Section Ethology Wapwingen Agricultural Unilbersip, P.O. Box 338, 6700 AH Wageningen, The Netherlands

Accepted 11 April 1996

Abstract

Vocalisations can be indicators of the physical state or condition of an animal, for instance the crow of a rooster. There are no published data on the temporal structure of crow sequences. In this paper 536 crows in 22 sequences of one red jungle fowl rooster (rooster 1) were recorded and analysed. Calls were very characteristic and there was little variation between the calls. Rooster I crowed with a mean latency of 287 s after onset of a light in the early morning. The average crow sequence consisted of 29 calls which lasted for 1416 ms on average. A gradual increase in pre-call interval was characteristic of each sequence. The variation in note durations is systematic and especially the last note correlated highly with the total call duration. Both the pre-call interval and the duration of the 4th note (doooo) may be parameters of fatigue and thus of physical condition. The number of crows in a sequence was positively related to air pressure outdoors. An experiment is

done in which the physical condition of a rooster (rooster 2) is manipulated by food deprivation. The results are analysed with single case randomisation tests. The number of crows in a sequence is significantly reduced after food deprivation, while the pre-call intervals are significantly increased. Prediction of the number of crows in the sequence can be done on base of the pre-call interval of the second call: both rooster 1 and 2 showed long pre-call intervals in short call sequences. Food deprivation and the possible loss of condition have a significant effect on the temporal structure of crow sequences and cause a decrease in the number of crows in a call sequence.

Key~vds: Red jungle fowl; Rooster: Vocalisation; Welfare indicator; Physical condition: Single-case analysis

’ Based on a contribution to the Bioacoustics Workshop ‘Numerical Methods for the Study of Vocalization in Animals and Man’ (Merbitz, Germany, 1995).

0376.6357/96/$15.00 Copyright 0 1996 Elsevier Science B.V. All right\ reserved

PII SO376-6357(96)00028-9

1. Introduction

Estimating the welfare of an animal is difficult, because inherently welfare has to do with subjective states, i.e., feelings or emotions. To estimate objectively the welfare of animals is thus impossible. However, indicators of feelings and/or emotions could be so-called emotional expres- sions or signals of the animals, although interpretation of the meaning of those indicators remains a problem. On the one hand, signals can be a reliable indicator of underlying emotions, but can on the other hand be used by the sender to deceive the receiver. Domestic roosters may deceive hens by food calling in absence of the food (Gyger and Marler, 19SS), although other explanations of the female approach behaviour are given (Van Kampen, 1994). Thus, variations in the use of vocalisations can be dependent on the context, in which we are interested, but also on the honesty of the animal. For this reason we have to be very careful with the interpretation of vocalisations as welfare indicators. Furthermore, we have to do with different aspects of an animal welfare, i.e., the physical and the psychological welfare.

Recently more research is done concerning vocalisations of animals as an indication of psychologi- cal welfare, for instance in captive baboons (Crowell Comuzzie, 1993). Some hen sounds correlate well with aspects of the environment of the hen, i.e., hens produce consistently the laying call when they are deprived of a laying nest, but also when deprived of a dust bath (Koene and Wiepkema, 1991). In battery cages this sound occurs more than in straw yard systems (Huber and Fiilsch, 1978) and is interpreted as an indication of decreased welfare in batteries. For research on vocalisations as welfare indicators more detailed studies of the information content and characteristics of sounds is needed. Analysis of the laying call is in progress. This call, however, shows an enormous variability. To investigate to what degree information can be extracted from vocalisations, temporal analysis of a more stereotyped and individually specific call, the rooster’s crow, is done.

Crowing has been the subject of a number of studies and is mostly described in onomatopoetic terms such as ki-ke-ri-ki, (German), coq-er-i-que (French), ku-ke-le-ku (Dutch), cock-a-doodle-doooo (American). Characteristically it consists of four notes (Fig. 1). Other sources describe the call

cock a doodle doooo

Fig. 1. Sonogram of one crow of rooster 1. The vocalisation notes mentioned further are note 1 = cock, note 2 = a, note 3 = doodle, note 4 = doooo). Total length displayed is 1.8 s. The lengths of the notes are mentioned in the text.

consisting of two to five notes (Miller, 1978). Roosters of the domestic fowl can start crowing the whole day through. When one rooster starts, others in the neighbourhood have also a higher probability of crowing. It is thought to be a means of declaring the presence of a territory and may be an indication of the rooster’s strength (red deer: Clutton-Brock and Albon, 1979) or status (Leonard and Horn, 1995). In this sense starting a call sequence is only meaningful when competing roosters are in the neighbourhood. However, another mechanism seems also to be involved, because solitary roosters start sequences at the beginning of the day. If the crow is an indication of strength of the rooster parameters in the call sequence can indicate physical strength or condition. Strength can be indicated in every call of a sequence (daily variation), but also during the sequence as fatigue increases (within-sequence variation). Because the functional morphology of the sound producing system of the chicken is not yet fully understood, no clear hypotheses concerning the effect of fatigue on parameters of the calls can be given. Possible parameters are increased pre-call intervals, or decreased in the number of calls in the sequence, in duration of the calls, in loudness and/or in production of energy intensive frequencies. Since we know that crows have very strong individual characteristics (Miller, 1978; Siegel et al., 1965) the duration can be a good indicator. On the other hand the heritability of the call duration is rather high, and day to day variation is limited (Siegel et al., 1965). Thus, to investigate the different parameters that are related to the initiation, duration and termination of the call sequence a detailed analysis of intervals and temporal structure of crows of the red jungle fowl rooster is done. Changes in vocal parameters will be discussed in relation to potential changes in physical condition. An experiment is done to determine the effect of loss of condition on the vocalisations. Deprivation of food during 0, 24 and 48 h and its effect on the call sequence is measured indoors.

2. Materials and methods

2.1. Subjects

The crows of one single red Burmese jungle fowl rooster (rooster 1) are recorded outdoors. No roosters were living in the neighbourhood. In a subsequent experiment one rooster (rooster 21 was tested in a sound proof chamber indoors.

2.2. Homing

Rooster 1 was housed with 7 hens in a cage of 3 X 3 X 3 m furnished with elevated perches, a nest box, and food and water available ad lib. The birds slept in an elevated hen roost with an entrance through the bottom and provided with perches and a wooden floor. A microphone and a light bulb were located in the ridge of the roost. Rooster 2 was kept in a wooden cage of 1 X 0.5 X 0.5 m in which water and dust bath were always available. The food container could be closed for deprivation.

2.3. Procedure

During the night, at 05:OO h, February and March 1993, an automated timer switched on the light bulb and a cassette recorder. Rooster I started crowing after the light was on. Audio recordings of 45

196 P. Koene/Behac~iouml Processes 38 (19%) 193-202

min were made. There were no other stimuli and/or disturbances present. The weather was recorded on a nearby station in Wageningen, ‘De Haarweg’, LUW Department of Meteorology. In the subsequent experiment (December 1995 and January 1996) the first call sequence of the day of rooster 2 was recorded in four conditions. The conditions were: no deprivation, food available (A), no deprivation, food not available (B), 24 h food deprivation (C) and 48 h food deprivation (D). The light and cassette recorder went on 07:OO h in the sound attenuated chamber. The experimental sequence was replicated twice, separated by two days without recordings.

2.4. Analysis

The analysis of the recorded call sequences is done on two levels: (1) the parametric analysis of call duration and pre-call intervals, using the vocalisation detector of Severns et al. (1985); and (2) the analysis of within-call notes and their durations and intervals using the Signal Sound Analysis System (Engineering Design, 1992). The time signal of a call was analysed as follows: the envelope was determined, smoothed, the gate function was determined, i.e., the signal was detected relative to a amplitude threshold (rms power) and the onset and offset locations in the gate function were determined, i.e., the starting and ending points of the notes and intervals within the calls. The call sequences of rooster 1 were analyzed as follows. Multiple regression was used to determine which parameters influenced the overall duration of the call. Furthermore, (partial) correlations between vocalisation parameters were calculated ( * = P < 0.05). Spearman correlations were calculated between call parameters and weather parameters of the day preceding and the day following the call sequence. Differences in the call parameters of rooster 2 in the four conditions were analysed using the restricted alternating treatments design (Barlow and Hersen, 1984; Onghena and Edgington, 1994) using the Single Case Randomisation Test package (Van Damme and Onghena, 1993).

-- - 0.2

0 i : ‘0 542.38 575 43 612 58 658 7 714 ia 786 29

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Fig. 2. Example of the temporal pattern of one crow sequence of rooster 1. The pre-call intervals (left y-axis) and call duration (right y-axis) are determined automatically by a vocalisation detector.

197

3. Results

Rooster 1 crowed with a mean latency of 287 k 240 s on 22 occasions (n = 22) after light onset. The latency to call correlated positively with percentage sunshine during the subsequent day (Spearman rho = 0.42, 12 = 22, P < 0.05). Mostly only one call sequence was produced per recording session with a mean of 28.57 k 6.21 calls per sequence and of 1416 k 38 ms duration. The number of calls in a sequence correlated positively with the local air pressure (Spearman rho = 0.42, y1 = 22, P < 0.05). No other correlations with weather parameters of the preceding or following day were found. An example of an individual call sequence is given in Fig. 2. Overall a gradual increase in pre-call interval is characteristic of each sequence. An increase of the pre-call interval and a decrease of call duration is found resulting in a highly negative correlation (Y = - 0.95 * ; n = 515) between pre-call interval and duration. Multiple regression analysis of individual calls showed that total duration of the call is a standard duration (1382 ms, n = 5 15) and a function of highly significant factors: the latency to vocalise (Standardised Regression Coefficient = - 0.398 X 1, the number in the sequence (- 0.27 1 *>, the day (0.247 * > and the preceding interval (0.119 * >. Generally the call sequence stopped when the pre-call interval exceeded 20 s (Fig. 21, although the pre-call interval of the second call correlated highly with the length of the call sequence (r = -0.678 *, n = 22) suggesting that the length of a sequence is predictable in an early stage. Analysis of the notes and inter-note intervals in the call sequence shows that the first note (note 1: 196 _t 1 1 ms, y1 = 536) shows first an increase in duration followed by a decrease, the second note (note 2: 155 + 10 ms> shows a gradual increase, the third note a gradual decrease (note 3: 518 * 17 ms>, and the 4th note shows a gradual decrease in duration and also the largest variation (note 4: 226 + 28 ms>. Intervals appear to be rather constant (il-2: 133 L- 8 ms; i2-3: 65 + 9 ms; i3-4: 122 + 23 ms>. In the course of a call sequence some changes in the duration of the notes and intervals are found, expressed in partial correlations with the call number in the sequence and controlling for the day effect (Table 1). The duration of the 1st note is not related to call number in the sequence, the 2nd note is positively related and the 3rd and 4th note are negatively related. The within-call analysis showed a high correlation between the total call duration and the last note (Table l), suggesting that variation in the total call duration is mainly dependent on the duration of the last note.

Rooster 2 crowed during the habituation period on each morning. The number of calls and the inter-call intervals are shown for the three replications in Fig. 3a-c. The average number of calls in a sequence was 17.67 t 9.55 in the 12 experimental days (range O-281, in condition A 24.67 + 1.15 calls ( IZ = 3; range 24-26 calls), in condition B 25.67 _t 2.52 calls (range 23-28 calls), in condition C

Table 1 Pearson partial correlations (controlled for daily variation) between the duration of the notes and other sequence parameters, i.e., the call number in the crow sequence (call number), the duration of the pre-call interval (pre) and the duration of the call

(call)

Note 1 Note 2 Note 3 Note 4 n calls

call no. - 0.045 0.540 * - 0.356 * - 0.263 * 536

prc -0.416* 0.585 * - 0.462 - - 0.07 1 515 call 0.241* - 0.024 0.234 * 0.75 1* 536

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Table 2 Mean duration of the interval before the second note in blocks of 5 calls in the three conditions. P values from single case randomisation test

Blocks Food (A) 0 h (B) 24 h (Cl P (A vs. B) P (B vs. C)

l-5 6.13 6.44 8.33 0.755 0.004 6-10 7.86 7.54 10.43 0.795 0.007

1 l-15 9.19 8.94 15.55 0.908 0.008

Inter-call 1-2 6.52 6.87 9.58 0.825 0.0261

Table 3 Mean duration of the combined 2nd, 3rd and 4th note in blocks of 5 calls in the three conditions. P values from single case randomisation test

Blocks

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1013 972 991

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1127 1112 1109

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1131 1145 1136

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0.024 0.012 0.012

15.33 It 0.58 calls (range 15-16 calls), and in condition D 5.00 jr 8.66 calls (range O-15 calls, i.e., on two days rooster 2 remained silent). The latency to crow did not differ between conditions. The number of calls per sequence differed significantly between conditions (systematic generation of 369600 randomisations: F-value for all conditions was 13.44, P = 0.001). The effect of deprivation (condition A, B vs. C, D) was highly significant (P = 0.002); food available vs. no food available (A vs. B) was not significant (P = 0.920); 24 h deprivation vs. 48 h deprivation (C vs. D) was not significant (P = 0.200). The pre-call intervals in the 24 h deprivation condition and the control conditions were significantly different (Table 2: first 15 calls divided into three groups in three conditions (A, B and C)). The pre-call interval between the first and the second call showed also a significant difference between conditions (Table 2). The first note showed a decrease in duration until the 5th call and an increase afterwards and remained constant after the 8th call (Fig. 4a); there were no differences between conditions A, B and C. The inter-note interval between the first and second note increases in duration and remained constant after the 8th call (Fig. 4b); there were no differences between conditions. The 2nd, 3rd and 4th note of the call of rooster 2 were detectable by ear, but merged into each other and were not detectable by the Signal analysis system. For analysis purposes they were taken together. The duration of these combined notes remained constant (Fig. 4~); the duration in condition A (food available) was significantly shorter than in conditions B and C (Table 3).

Fig. 3. (a) Pre-call interval of rooster 2 in relation to the crow number in the sequence for the four conditions in the first crow series. (b) Pre-call interval of rooster 2 in relation to the crow number in the sequence for the four conditions in the second crow series. (c) Pre-call interval of rooster 2 in relation to the crow number in the sequence for the four conditions in the third crow series.

200 P. Koene / Brhariourul Processes 38 (19961 193-202

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4. Discussion

A total of 536 crows in 22 sequences of one rooster were analysed. Calls were very characteristic and there was little variation in the calls. According to Siegel et al. (19651, who emphasise the genetic basis of crow parameters, 3 or 4 calls per male are enough to get a reliable estimate of call duration. The variation, however, seemed to be rather systematic in the course of the sequence, and thus serial measurement is needed to reveal the meaning of these systematic changes. The pre-call interval increased, the duration of the 2nd note increased, the duration of the 3rd and 4th decreased. Especially the last note correlated highly with the total call duration and can be a good candidate as parameter of fatigue and thus physical condition. Miller (1978) reported the same correlation for a number of roosters as the only within-call correlation found. The total number of calls in a sequence was at first thought to be an indicator of physical condition. Also, the pre-call interval between the first and the second call correlated negatively with the total number of calls in the sequence. The multiple regression analysis showed that motivational and physical differences can both cause differences in call duration. Presumed high motivation (short latency to call, and calling later in the year) increases the call duration, while presumed fatigue (calls late in the sequence and relatively short intervals between calls) decreases call duration. Thus, daily and sequential variation in call duration can indicate variation in strength, but also in motivation to crow. So pre-call intervals and the duration of the whole sequence cannot be interpreted unambiguously in terms of physical condition. However, the results of food deprivation on crowing in rooster 2 confirmed the correlational results found in the crowing of rooster 1. The interval between the first and second call differs significantly between condition B and C as did the number of crows of the sequence. Food deprivation increases the pre-call interval and decreases the number of crows in a sequence. The Signal system was not able to detect the 4th note of the crow. Correlations concerning this note found in rooster 1 could not be confirmed in the experiment. The deprivation duration has no significant effect, but this is possibly due to the second replication. Furthermore, the effect of the food availability of the duration of the combined 2nd, 3rd and 4th note has to be investigated further. More experiments are in progress in which the condition and the motivation of the rooster are influenced. It is essential to study more roosters, alone and in contest, to find further indications of physical strength in the crow of the red jungle fowl. Frequency analysis, more individuals and more complex vocalisations (laying call) are the next steps in the analysis of vocal indicators of welfare of chicken.

References

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Clutton-Brock, T.H. and Albon, S.D., 1979. The roaring of red deer and the evolution of honest advertisement. Behaviour, 69: 145- 170.

Fig. 4. (a) Mean first note duration (n = 3) of rooster 2 in conditions A, B and C. (b) Mean interval between the first and the second note (n = 3) of rooster 2 in conditions A, B and C. (c) Mean duration of the sum of the 2nd, 3rd and 4th note (n = 3) of rooster 2 in conditions A, B and C.

202 P. Koerw /Brhur~iourcrl Processes 38 (19961 193-202

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