The effects of allogrooming and social network position on behavioural indicators of stress in female lion-tailed macaques (Macaca silenus).

Allogrooming serves an important social function in primates and confers short term benefits such as parasite removal and stress-relief. There is currently mixed evidence as to the immediate impact of allogrooming on an individual's stress levels, which may be influenced by their role in the grooming dyad, position in their social network, or their relationship with their grooming partner. In this study of seven captive adult female lion-tailed macaques (Macaca silenus) in a mixed sex group at Chester Zoo, UK, we found evidence to support a tension-reduction function of allogrooming. Focal animal sampling showed that the duration of self-directed behaviour (SDB), which indicates moderate to high levels of stress, was significantly lower in the five-minute period following allogrooming than the five-minute period preceding it for both recipients and groomers. However, when compared to match-control periods, both SDB rates and durations were significantly lower across all individuals in the five-minute period both before and after allogrooming, indicating that although allogrooming reduces stress, it is also more likely to occur when individuals are already in a relatively relaxed state. The rate and duration of SDB post-grooming did not correlate with the strength of a dyad's bond (based on proximity). This suggests that it is the act of allogrooming itself, rather than the identity of the partner, that reduces stress for both parties. Analysis of the proximity network highlighted a clear cost to social integration; node strength, a measure of the number and strength of an individual's direct relationships, positively correlated with the duration of self-directed behaviour, suggesting that more gregarious individuals may experience higher levels of stress. These findings add to the growing body of literature that examines the effect of the individual social environment on primate stress levels, and also highlight the need to further investigate the link between social integration and the stress experienced by group-living animals.

Taxonomic and geographic bias in 50 years of research on the behaviour and ecology of galagids.

Identifying knowledge gaps and taxonomic and geographic bias in the literature is invaluable for guiding research towards a more representative understanding of animal groups. Galagids are nocturnal African primates and, for many species, detailed information on their behaviour and ecology is unavailable. To identify gaps and bias in the literature we reviewed published peer-reviewed research articles on galagid behaviour and ecology over a 50-year period from January 1971 to December 2020. Using the Web of Science and Google Scholar databases, we identified 758 articles, assessed 339 full texts for eligibility and included 211 in the review. Species of Otolemur have been extensively researched in comparison to other genera (78.2% of studies; Euoticus: 13.3% of studies; Galago: 66.4% of studies; Galagoides: 20.9% of studies; Paragalago: 22.3% of studies; Sciurocheirus: 15.2% of studies). The most common category of research was physiology (55.0% of studies), followed by behavioural ecology (47.4% of studies), and fewer studies were on genetics and taxonomy (16.1% of studies) and habitat and distribution (14.2% of studies). Text mining revealed that the word 'behaviour' was the most common word used in abstracts and keywords, and few words were related to ecology. Negative binomial regression revealed that mean body mass and geographic range size were significant positive predictors of the total number of scientific outputs on each species. Research on wild populations was carried out in only 24 (60%) of the 40 countries galagids are thought to inhabit. Studies were undertaken in locations with lower mean annual temperatures and higher human population densities over warmer and less populated areas. We encourage a more equal sampling effort both taxonomically and geographically that in particular addresses the paucity of research on smaller species and those with restricted ranges. Research on in situ populations, especially in warmer and remote areas, is urgently needed, particularly in West, Central and some Southern African countries.

Vocal Repertoire and Intraspecific Variation within Two Loud Calls of the Small-Eared Greater Galago (Otolemur garnettii) in Tanzania and Kenya.

Vocal repertoires and call structure can provide insights into the behaviour and evolution of species, as well as aid in taxonomic classification. Nocturnal primates have large vocal repertoires. This suggests that acoustic communication plays an important role in their life histories. Little is known about the behavioural context or the intraspecific variation of their vocalisations. We used autonomous recording units and manual recorders to investigate the vocal behaviour and structure of loud calls of the small-eared greater galago (Otolemur garnettii)in Kenya and Tanzania. We describe the vocal repertoire, temporal calling patterns and structure of 2 loud calls of 2 subspecies: O. g. panganiensis and O. g. kikuyuensis. We found considerable intraspecific structural differences in both loud calls. These are congruent with the current subspecies classification. Differences in vocalisations among populations are not consistent with the "acoustic adaptation hypothesis," rather they are likely a result of geographic variation due to isolation caused by vegetational barriers in southern Kenya.

Sleep patterns, daytime predation, and the evolution of diurnal sleep site selection in lorisiforms.

OBJECTIVES: Synthesize information on sleep patterns, sleep site use, and daytime predation at sleep sites in lorisiforms of Asia and Africa (10 genera, 36 species), and infer patterns of evolution of sleep site selection. MATERIALS AND METHODS: We conducted fieldwork in 12 African and six Asian countries, collecting data on sleep sites, timing of sleep and predation during daytime. We obtained additional information from literature and through correspondence. Using a phylogenetic approach, we established ancestral states of sleep site selection in lorisiforms and traced their evolution. RESULTS: The ancestral lorisiform was a fur-clinger and used dense tangles and branches/forks as sleep sites. Use of tree holes and nests as sleep sites emerged ∼22 Mya (range 17-26 Mya) in Africa, and use of bamboo emerged ∼11 (7-14) Mya in Asia and later in Africa. Fur clinging and some sleep sites (e.g., tree holes, nests, but not bamboo or dense tangles) show strong phylogenetic signal. Nests are used by Galagoides, Paragalago, Galago and Otolemur; tree holes by Galago, Paragalago, Sciurocheirus and Perodicticus; tangles by Nycticebus, Loris, Galagoides, Galago, Euoticus, Otolemur, Perodicticus and Arctocebus; all but Sciurocheirus and Otolemur additionally sleep on branches/forks. Daytime predation may affect sleep site selection and sleep patterns in some species of Nycticebus, Galago, Galagoides, Otolemur and Perodicticus. Most lorisiforms enter their sleep sites around sunrise and leave around sunset; several are active during twilight or, briefly, during daytime. CONCLUSION: Variations in sleep behavior, sleep patterns and vulnerability to daytime predation provide a window into the variation that was present in sleep in early primates. Overall, lorisiforms use the daytime for sleeping and no species can be classified as cathemeral or polycyclic.

Predation as a determinant of minimum group size in baboons.

Predation risk places a pressure on animals to adopt mechanisms by which they reduce their individual risk of being preyed on. However, a consensus on methods of determining predation risk has yet to be reached. One of the most widespread ways in which animals respond to predation risk is by living in groups. Minimum permissible group size is the smallest group size that animals are able to live in, given the habitat-specific predation risk they face. We explore ways in which predation risk can be measured and analyse its effect on minimum observed group size in baboons. Using data on predator density, habitat composition and baboon body size, we investigate the impact of the components of predation risk on baboon group size, and derive an equation that best predicts minimum group size. Minimum group size in baboons is related to predator density and female body mass. Both of these elements can, in turn, be estimated from environmental variables. These findings present support for the argument that group living in primates is a response to predation risk and offer potentially new ways of investigating carnivore and primate ecology.