Scent-marking behaviour and semiochemistry in the Callitrichidae

Olfactory communication is an important mediator of social interactions in mammals, providing information about an individual’s identity and current social, reproductive, and health status. Callitrichids (i.e. marmosets and tamarins) constitute a good model for the study of olfactory communication, as they make use of a range of odour signals. Callitrichids conspicuously deposit odorous secretions, produced by specialized scent-glands, on branches in their environment, a behaviour called scent-marking. Several functions have been attributed to callitrichid scent-marking behaviour, including advertisement of reproductive and dominance status, and of identity, territorial defence, and spatial orientation and signalling of food resource location. The present doctoral project combined behavioural and chemical information to investigate callitrichid olfactory communication. The study explored how environmental, social, and reproductive aspects might influence patterns of callitrichid scent-marking behaviour, as well as the chemical composition of scent-gland secretions and urine used to convey chemosignals. Behavioural observations, along with swabs of scent-glands, and of naturally deposited scent-marks and urine, were collected from captive groups of bearded emperor tamarins, Saguinus imperator subgrisescens, cotton-top tamarins, Saguinus oedipus, and silvery marmosets, Mico argentatus, in three British zoos. Chemical samples were analysed using headspace gas chromatography-mass spectrometry (GC-MS). In addition, scent-gland secretion samples were collected from a wild population of sympatric emperor tamarins and Weddell’s saddleback tamarins, Leontocebus weddelli, during an annual capture-and-release programme in the south-eastern Peruvian Amazon. These samples were analysed using both in situ and laboratory-based GC-MS techniques. I established the existence of unique chemical signatures of species, groups, sex, reproductive status, and the individual, in callitrichid scent samples, which were matched with differences in scent-marking behaviour. My results support the assumption that chemosignalling plays an important role in the advertisement of identity, reproductive state/status and dominance in this taxon. Moreover, I showed that the social context, as well as spatiotemporal aspects of scent-marking deposition, influenced scent-marking activity. Further differences in the characteristics of scent-marking deposition revealed in this study, both at behavioural and chemical levels, may reflect variable strategies of communication to ensure that signals are transmitted to the intended receivers, which is especially relevant for sympatric species. I identified a number of putative semiochemicals (i.e. chemicals involved in communication) from the scent samples of captive and wild callitrichids. Notably, I presented results from the first use of the Torion® portable GC-MS for in situ analysis of wild mammal scent samples. In addition, I revealed differences in the chemical composition of tamarin scent-gland secretion samples between wild and captive conditions, which may indicate an effect of captivity on the chemicals produced. This study provides knowledge of mammalian olfactory communication systems, applicable to captive husbandry practices, including conservation breeding programmes of rare species.