Loud Calls, Startle Behaviour, Social Organisation and Predator Avoidance in Arboreal Langurs (Cercopithecidae: Presbytis)

Abstract

Linking predator avoidance and social organisation predicts that large groups are favoured under heavy predation pressure but that small, inconspicuous groups may do equally well by avoiding detection altogether. We explored the relationships between antipredator behaviour (vocalisation, concealment, fleeing), detectability (colouration, group size) and social organisation in arboreal langurs. Three clear antipredation conditions emerged: (1) exemplified by Presbytis melalophos – brightly-coloured species (red, yellow) with contrasting colours, living in large unimale-multifemale groups (>10 individuals), that vocalised frequently and that flee loudly through the canopy; (2) exemplified by P. comata – greyish species (some contrasting colours), living in intermediate, unimale-multifemale or 1-male-1-female groups (approx. 7 individuals), that vocalise infrequently and that flee through the middle forest layers; (3) exemplified by P. frontata – dull-coloured species without contrast, living in small unimale-multifemale or 1-male-1-female groups (<5 individuals), that may freeze upon detection, and that may vocalise mainly during the night. Crypsis as an antipredator strategy is restricted to taxa that occur in 1-male-1-female groups. This wide range of antipredator strategies within a monophyletic taxon living in the same general area with a similar suite of predators facing similar predator pressures appears to be unique among the order Primates.

Group Composition and Monandry in Grizzled Langurs, Presbytis comata, on Java

“…Over the last 3 or 4 decades, partially aided by molecular phylogenetic analysis [Meyer et al, 2011;Vun et al, 2011] and partially by adopting different species concepts [Groves, 2001], the number of species has increased from 8 [Davies and Oates, 1994] to 17 [Zinner et al, 2013]. While Bennett and Davies [1994] concluded that differences in socioecological behaviour in Presbytis langurs appear to be due to differences in habitat rather than to intrinsic differences between species, when group size, morphology and antipredator behaviour are taken into account, the genus can be divided into 3 distinct groups [Nijman and Nekaris, 2012]. First are the ones that live primarily in large groups, comprising 1 or 2 adult males with several adult females plus offspring, and that are typically brightly coloured and vocal when disturbed (e.g., banded langur, P. femoralis [Curtin, 1980]; red langur, P. rubicunda [D'Agostino et al, 2016]).…”

“…Third are species that live in 1-male/1-female groups, and where individuals are dark in colour and that rely on crypsis as an antipredator strategy (e.g., Siberut langur, P. siberu [Tilson and Tenaza, 1976]). The available data for at least 1 species , the white-fronted langur P. frontata , is suggestive of a monandrous social organization (sensu Tenaza and Fuentes [1995]) i.e., 1-male/multifemale and 1-male/1-female groups coexist in a single population 1 [Nijman and Nekaris, 2012]. Too few data are available for a number of species regarding their socioecology to make firm conclusions (e.g., Natuna langur, P. natunae [Lammertink et al, 2003;Nijman and Nekaris, 2012]), or there are conflicting reports or apparent differences in interpretation concerning a species' social organization.…”

“…In primates, Opie et al [2013] found evidence for linked evolution between social monogamy and discrete female ranging patterns (with little overlap between females), biparental care, and risk of male infanticide. In the approximately 150 species of Old World monkeys, the group to which P. comata belongs, social monogamy has been reported, often with mixed evidence, in De Brazza's monkeys ( Cercopithecus neglectus ) and P. siberu , whereas monandry has been reported in P. frontata and the simakobu Simias concolor [Watanabe, 1981;Leutenegger and Lubach, 1987;Tenaza and Fuentes, 1995;Nijman and Nekaris, 2012]. Sexual dimorphism is pronounced in C. neglectus and S. concolor , but not in P. frontata or P. potenziani ; extensive range overlap is present in C. neglectus and P. potenziani , but not in S. concolor , and direct evidence of infanticide is lacking for all 4 species.…”

The Behavioural Contexts of Red Langur (Presbytis rubicunda) Loud Calls in the Wehea Forest, East Kalimantan, Indonesia

“…For example, in some species, primate loud calls help regulate social encounters including, but not limited to, behavioural contexts such as mate attraction, the rallying of conspecifics, and territorial defence [Robinson, 1979[Robinson, , 1981Byrne, 1982Byrne, , 1983Kinzey and Robinson, 1983;Mitani and Marler, 1987;Gautier, 1998;Gouzoules and Gouzoules, 2002;Wich and Nunn, 2002;Nijman and Nekaris, 2012]. Another possible function of loud calls is alarm/predator defence; that is, many species make loud, conspicuous calls in response to predators, which can alert group members to the presence of a predator and elicit antipredator responses from conspecifics as well as deter the predators themselves [Struhsaker, 1967;Seyfarth et al, 1980;Zuberbühler, 2001;Nijman and Nekaris, 2012].…”

The Evolution of Cognition in Primates, Including Humans

“…Similarly, langurs (Presbytis spp.) display significant variation in their responses to human intruders (e.g., Nijman & Nekaris, 2012).…”