Radio Telemetry of Heart-Rate in Male Tammar Wallabies (Marsupialia, Macropodidae) - Temporal Variations and Behavioral-Correlates

A group of tammar wallabies consisting of three males and four females was kept in an enclosure of 800 m2. Behavioural data on all animals and the heart rate of the males were recorded simultaneously by combined telemetric and computer equipment. The overall mean heart rate of the three males correlated with their age and social status, with the highest value for the youngest and lowest ranking animal. Overall variability of heart rate was lowest in the mid-ranking male. Heart rate fluctuated within infra-, circa-, and ultradian time scales, and the patterns exhibited considerable variability both between and within individuals. In all males infradian changes were irregular and could not be correlated with general activity, with the frequency of agonistic or sexual behaviour, or with changing ambient temperatures. Within the 24-hour scale a regular pattern was observed in all males. This circadian rhythm was characterised by stationary positions of two maxima at dusk and dawn. Circadian fluctuations of all males occurred simultaneously and were positively correlated with activity level, though some cases revealed an independence of heart rate and activity. There were also ultradian variations attributable to motor activity with sexual and/or agonistic behaviour or non-interactive behaviour including locomotory activity. A differentiated behavioural categorisation and the assessment of individual variability of heart rate during social encounters are necessary if motoric and arousal components are to be distinguished.