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

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 1 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.