Differences in behaviour and physiology between adult surrogate-reared and mother-reared Cynomolgous monkeys (Macaca fascicularis)
SourceFolia Primatologica, 71, 2000, (2000), pp. 201
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SW OZ DCC BI
Previous studies of the effects of rearing conditions on exploratory behaviour revealed that 80% of monkeys reared in peer groups with surrogate mothers developed neophobia, whereas only 15 % of mother-reared monkeys did. Young surrogate-reared and, especially, isolated rhesus monkeys are known to be fearful, to show stereotypic movements and to have abnormal levels of catecholamines in the cerebrospinal fluid. Since the neophobia of our monkeys persisted throughout adulthood we were interested in comparing the incidence of stereotypies and the level of catecholamines in adult surrogate- and mother-reared cynomolgous monkeys. We compared the type of stereotyped movements and the time spent on these in 7 surrogate-reared and 8 mother-reared adult monkeys. We found that both mother-reared and surrogate-reared monkeys spent the same amount of time on stereotyped behaviour, hut the stereotyped movements they performed were of a different kind. Mother-reared monkeys showed primarily stereotypies that include locomotion, whereas surrogate-reared monkeys showed mainly repetitive movements of parts of the body. Locomotor stereotypies are seen as a normal response to an abnormal environment, so called 'cage-stereotypies'. Repetitive body-part movements are viewed as 'deprivation-stereotypies', which unlike 'cage-stereotypies' are extremely difficult to disrupt. Some researchers have found differences in the neurobiological status between surrogate-reared and mother-reared monkeys. We also examined the levels of catecholamines in 24-h urine under baseline conditions and under conditions of stress, by means of high-performance liquid chromatography and fluorometric detection. Under both conditions, surrogate-reared monkeys excreted significantly higher levels of adrenaline, noradrenaline and dopamine than their mother-reared conspecifics did. It is assumed that an increased activity of the adrenal medulla forms a part of the mechanisms that are involved in anxiety disorders in man.
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