Abstract
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.
Highlights
We are losing species worldwide at such an alarming rate that we may be in the midst of the sixth mass extinction [1]
There has been an increase in research into galagids from the late 1990s onwards (Fig 2) and the maximum number of studies published on galagid behaviour and ecology in any year (2016) was 13
At least one author from a USA-based affiliation contributed to 132 studies (62.6%), at least one South African affiliation was connected to authors of 42 studies (19.9%) and at least one UK affiliation featured in 32 studies (15.2%)
Summary
We are losing species worldwide at such an alarming rate that we may be in the midst of the sixth mass extinction [1]. Research effort in animal behaviour and ecology is often dominated by a focus on certain taxonomic groups [4] and geographical study areas or biomes [5, 6]. Reviews have revealed taxonomic bias (when organisms from a particular taxonomic group are researched disproportionately to others) in studies across a wide range of biological disciplines [9, 10] as well as a lack of species-specific data in subjects such as animal behaviour [4] and conservation biology [7, 8, 11,12,13,14]. Mammals and birds receive more research attention than any other group relative to their number of species [15, 16]. Even within these well studied groups there can be imbalances, for example within European bird studies there is a strong focus on certain species [17], and the same has been found within studies on Australian terrestrial mammals [9] and Neotropical primates [18]
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