With 194 species and subspecies, the prosimians comprise 27% of living primates. The majority are lemurs (112), 32 are galagos, 19 are tarsiers, and 21 are of the Family Lorisidae: the pottos, five, and angwantibos, just two, in Africa, and the slender and slow lorises, 14, in Asia. This extraordinary and highly specialized radiation of nocturnal insectivores was for many years largely ignored: small, difficult-to-watch, and seemingly torpid little fur balls lacking ambition. With few exceptions—pioneers Simon Bearder and Pierre Charles-Dominique in particular—they failed to excite the fevered pursuits of anthropologists and primatologists through the 1970s and 1980s. But, as Bearder says in his foreword: ‘Gradually, over the years, the number of researchers attracted by the delights of nocturnal primate research became significant’. As told by Anna Nekaris and Anne Burrows, it became clear that the Lorisidae's fascinating ways, habits and adaptations deserved a book.
Following a comprehensive introduction by the editors, the chapters are divided into three sections. The first, ‘Evolution, morphology and the fossil record’, starts with a brief history of the discovery, descriptions and distinctions of the four genera recognized today. The next chapter discusses the sparse (only seven species named), but nonetheless informative fossil record, with the earliest genus, Namaloris, dating from the Oligocene. The section includes seven essays investigating the functional morphology of various distinctive traits that are evidently significant in the lorisids’ nocturnal way of life. Three concern their sensory systems—sight (orbit orientation), smell (olfactory system anatomy and sensitivity) and touch (the ecology of face or vibrissal touch)—another looks at the soft tissue anatomy of the hand that is highly derived in the potto but less so in the slow loris, and a fifth at the biomechanics of their locomotion, involving so-called quadrumanous climbing and gripping, to move along, sit on, and hunt among thin branches in dense vegetation. Two chapters consider the adaptive morphology of the dental toothcomb. One concerns the fossil evidence from Karanisia clarki, the earliest strepsirrhine to possess one, concluding that it was used as a comb but also to scrape up gum. The other discusses the role of gum-feeding (unusual in primates, but a specialization for some) in loris evolution, examining the associated dental adaptations and signatures. This first section is rounded off by an excellent review of the evolution of the social behaviour that characterizes the Lorisiformes, including as such the galagos.
The second section focuses on behaviour, ecology and captive management. The first chapter deals with the search for appropriate diets for captive lorises and galagos based on what is known of their feeding habits in the wild. A second discusses the history of lorises in captivity and the importance of zoo records, and a third reviews and recommends best practices for their breeding and husbandry. The ecology and behaviour section comprises eight chapters, covering behavioural research in the wild, including visual function and ecology, thermoregulation (lorises), home range and activity budgets, a general review of what is known of potto and angwantibo behaviour, positional behaviour and substrate preference, feeding and foraging of released Philippine slow lorises, ranging patterns of the pygmy slow loris in Cambodia, and mother–infant interactions and behaviour of captive Sunda lorises.
Lorises being small, often solitary, night-owls, a number of the chapters in the second section are revelatory in the creative methods used to study them in the wild: identifying them and following them to record their activities and diets, and their foraging, ranging and social behaviour. Five chapters in the third section, ‘Research, trade and conservation’, cover research methods: censusing, data collection, the sophisticated equipment and techniques used, and the precautions and care required in trapping and collaring them. Notable is a box that explains the need for the use of red light when observing them—white light disturbs them and probably damages their sensitive eyes.
All of the nine slow loris species, Nycticebus, are categorized as threatened on the IUCN Red List, two as Critically Endangered. The red slender loris Loris tardigradus of Sri Lanka is also Endangered, and the grey slender loris Loris lydekkerianus of Sri Lanka and India is, for the moment at least, considered Least Concern. Too little is known of the pottos Perodicticus and angwantibos Arctocebus, but the Benin potto Perodicticus juju is categorized as Endangered. Declines in their numbers result from the destruction of their habitats and from hunting for human consumption and the wildlife trade. Following a review of the distribution and conservation status of the pygmy loris and Bengal slow loris in China, the remaining five chapters cover the appalling international and domestic commercial trade in lorisids for bushmeat and medicinal purposes, and as pets and photo props in social media, the latter particularly affecting the lorises. In South-east Asia, horrific numbers of slow lorises are cruelly traded in wildlife markets for medicinal purposes. The chapters also cover the considerable efforts underway to combat this abuse and slaughter.
This is a benchmark compendium for our understanding of these creatures—a small but truly fascinating outpost of the primate radiation.
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