Heart rate and social status among male cynomolgus monkeys (Macaca fascicularis) housed in disrupted social groupings

Abstract

The relationship between social status and telemetrically recorded heart rate (HR) was studied among 29 adult male cynomolgus monkeys (Macaca fascicularis) which had been maintained in six social groups (n = four or five) for 26 months. The membership of each group was reorganized periodically (20 times in 26 months) by shifting monkeys from group to group in a way that maximized each animal's exposure to social strangers. The social behavior of all animals was monitored, via focal sampling, twice per week; social status was based on the outcome of agonistic encounters and was determined every 2 weeks. For four nights on each of two occasions (months 13 and 25 of the experiment), the HRs of all animals were sampled 12 times per hour, 30 seconds per sample between 1800 h and 0900 h. A more limited nocturnal HR sampling was performed during the first month of the experiment. The behavioral observations revealed that, despite the repeated social reorganization, some monkeys were habitually dominant in their groups while others were consistently subordinate. Further, those monkeys falling above the median in dominance status had significantly lower HRs than their subordinate counterparts (104 vs. 117 beats per minute; P = 0.01). The effect was observed irrespective of the month in which observations were made, and was corroborated by more limited observations made at the beginning of the experiment. Finally, those few monkeys which rose or fell in rank were characterized by inverse changes in HR, supporting the hypothesis that behavioral factors influence HR (rather than visa versa).

Stability of social status rankings of female cynomolgus monkeys, of varying reproductive condition, in different social groups

“…This finding implies that dominants and subordinates have different characteristics or traits which contribute to their social status. This implication is in keeping with several recent reports which also suggest that traits may characterize animals of differing social status [Shively et al, in press;Kaplan et al, 1990;Sapolsky & Ray, 19891. The similarity in the association between ranks in all social situations to the association found between the ranks of females that lived in unique social groupings is perhaps unexpected. However, when individuals are repeatedly reorganized, alliances formed in prior social groupings are disrupted, and new alliances must be formed.…”

Central Nervous System Monoamine Correlates of Social Dominance in Cynomolgus Monkeys (Macaca fascicularis)

“…As in previous studies, social status was determined on the basis of fight outcomes in dyadic encounters (Kaplan et al 1982(Kaplan et al , 1990(Kaplan et al , 1996. A fight was defined as an attack of any intensity followed by flight of any intensity (Sade 1967).…”

“…The same approach has been used previously in similarly designed studies with respect to the prediction of coronary artery atherosclerosis, heart rate, adrenocortical response to challenge, and resistance to infection. (Kaplan et al 1982(Kaplan et al , 1986(Kaplan et al , 1990Cohen et al 1997). Nonetheless, because average rank for the experiment is based largely on data separated in time from the collection of CSF, additional analyses were conducted based on ranks determined at the time of CSF collection.…”

Effects of Exercise on Cardiovascular Outcomes in Monkeys With Risk Factors for Coronary Heart Disease

“…11 Briefly, HR was measured by using portable ECG telemetry units (Keuffel and Esser, Model TM-7 patient monitors) secured beneath nylon mesh jackets and maintained in place for several days. To assess the effects of the experimental manipulations, HR was monitored during undisturbed overnight conditions (the 18-hour period from 15:00 until 09:00, recorded on 3 consecutive nights) at baseline and 4 times during the experiment.…”