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.

Cryptic diversity and species boundaries within the Paragalago zanzibaricus species complex.

The recently described genus Paragalago is a complex of several nocturnal and morphologically cryptic species distributed in the forests of eastern Africa. Species diversity within this genus has been mainly described using species-specific differences in their loud calls. However, molecular data are still lacking for this group and species boundaries remain unclear. In this study, we explore species diversity within the zanzibaricus-complex using a combination of mitochondrial and nuclear data and comparing multiple species delimitation methods. Our results consistently support the existence of three independent lineages, P. cocos, P. zanzibaricus, and P. granti, confirming previous hypotheses based on vocal data. We conclude that these three lineages represent valid cryptic species and we hypothesize that speciation within this complex was characterized by cycles of forest expansion and contraction in the Plio-Pleistocene.

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.