Asia's slow and slender lorises (Nycticebus and Loris) are among nature's most extreme primates. Until recently, it was not understood why lorises have such huge forward-facing eyes, strange steady climbing locomotion, tiny dependent babies, and a bite that potentially can kill a human! Indeed, early studies described them as slow, solitary, and boring. Twenty years of field research now indicate that lorises are among the most intriguing mammal species.

Both predator defense and feeding ecology models have been proposed to explain the relatively slow climbing locomotion of the Lorisinae. During a study of the socioecology of the Mysore slender loris (Loris tardigradus lydekkerianus) in Tamil Nadu, India, six categories of behavior and eleven different postures were recorded to estimate a general activity budget for the slender loris, and are examined here particularly in relation to slow climbing locomotor strategies. Reactions to potential predators are also described. The main study population was composed of 15 animals. Activity budgets were compiled in three ways: all instantaneous point samples collected over 1,173 h pooled (n = 13,717), the means of individual lorises (n = 15) and behavior at the moment of first contact (n = 357). No significant difference was found between these three data sets. Approximately 45% of the activity budget was spent in inactive behaviors including sitting vigilant, resting and sleeping. Foraging and traveling comprised nearly half the activity budget, with the rest of the time spent grooming. The most common postures assumed by lorises were sitting and quadrupedal walking. Individual lorises were relatively gregarious and spent up to half their activity budget with other animals. Unlike pottos and angwantibos, lorises did not freeze, head butt or drop from branches in reaction to potential predators, but either ignored them, fled or made loud calls. Cryptic and slow climbing locomotion were used before traveling on open ground between discontinuous substrates, thereby supporting hypotheses relating to predator pressure, and also before capturing fast moving insect prey, supporting hypotheses relating to diet. It is proposed that a divergence in foraging strategies between bushbabies and lorisines may be the best adaptive explanation for their behavioral and morphological differences, including predator defense mechanisms.

Loris lydekkerianus lydekkerianus has been shown to have a promiscuous copulatory pattern, to maintain social networks via frequent loud calls, to interact socially throughout the night with all age classes, and to sleep socially. Though these behaviors point towards a multimale social system, no study of their spacing system has yet been provided to support this view. From October 1997-August 1998, I conducted a study of the Mysore slender loris in Ayyalur, India. During 1,400 field hours, data were collected on range use of 3 adult females, 3 adult males, 1 subadult female, and 1 subadult male. Lorises slept in groups averaging 4 individuals, composed of an adult female, her offspring, and 1-2 adult and subadult males. Sleeping sites for three groups were located within 1.9 ha in the center of the study area. The minimum convex polygon in hectares encompassing each animal's range was determined, as well as overlap among home ranges of individual lorises. Average home range sizes were: adult males, 3.6 ha +/- 0.09; subadult/smaller males, 1.17 ha +/- 0.26; and adult and subadult females, 1.59 ha +/- 0.24. Male ranges overlapped with at least 2-3 other adult males (0.72 ha +/- 0.23). Female ranges overlapped slightly with at least 2 other female ranges (0.22 ha +/- 0.25). Male ranges overlapped those of at least 3 females (0.82 ha +/- 0.51). Patterns of home range and sleeping site support previous suggestions of a multimale social system, similar to aye ayes and some galagos.

Few primate species are known to excavate plant sources to procure exudates and other foods via active gouging. It is now apparent that slow lorises belong to this rare guild of obligate exudativorous primates. We investigate the diet of the pygmy loris (Nycticebus pygmaeus) in a mixed deciduous forest in the Seima Protection Forest, Eastern Cambodia, and attempted to determine the importance of this resource in their diet. Feeding behaviors of six females and seven males were observed using radio-tracking to facilitate follows, and nine fecal samples were collected in February-May and January-March in 2008 and 2009 respectively. We observed 168 feeding bouts, during which the animals ate exudates (76); fruits (33); arthropods (27); flower parts (21); fungi (3); parts of bamboo culms (7); and reptiles (1). We filmed 19 bouts of exudativory, and observed animals consuming exudates in an orthograde posture, or standing quadrupedally over the exudate source. Pygmy lorises also gouged bamboo to collect lichen and fungi, or broke open dead culms to access invertebrates. Feeding occurred on terminal tree branches (24), tree trunks (21), bamboo (13), the middle of branches (7), and the undergrowth (1). The fecal samples contained plant parts, small-sized arthropods (primarily Coleoptera and Lepidoptera), reptile scales, animal bones, and animal hairs. Pygmy slow lorises are morphologically specialized for processing and digesting exudates, displaying small body sizes, specialized dentitions, elongated, and narrow tongues, large caecums, short duodenums, expanded volar pads, and modified hindlimbs. These features, combined with the prevalence of exudates in their diet across seasons, and ill health when exudates are missing from their diet in captivity, points to this species being an obligate exudativore.

This paper examines the importance of vision in the lives of nocturnal primates in comparison to diurnal and cathemeral species. Vision is the major sense in all primates and there is evidence that the eyesight of nocturnal species is more acute and variable than has previously been recognized. Case studies of the behaviour of a galago and a loris in open woodland habitats in relation to ambient light show that Galago moholi males are more likely to travel between clumps of vegetation along the ground when the moon is up, and during periods of twilight, whereas they retreat to more continuous vegetation and travel less when the moon sets. This is interpreted as a strategy for avoiding predators that hunt on the ground when it is dark. The travel distances of Loris lydekkerianus are not affected by moonlight but this species reduces its choice of food items from more mobile prey to mainly ants when the moon sets, indicating the importance of light when searching for high-energy supplements to its staple diet. Evidence is presented for the first time to indicate key aspects of nocturnal vision that would benefit from further research. It is suggested that the light and dark facial markings of many species convey information about species and individual identity when animals approach each other at night. Differences in the colour of the reflective eye-shine, and behavioural responses displayed when exposed to white torchlight, point to different kinds of nocturnal vision that are suited to each niche, including the possibility of some degree of colour discrimination. The ability of even specialist nocturnal species to see well in broad daylight demonstrates an inherent flexibility that would enable movement into diurnal niches. The major differences in the sensitivity and perceptual anatomy of diurnal lemurs compared to diurnal anthropoids, and the emergence of cathemerality in lemurs, is interpreted as a reflection of evolution from different ancestral stocks in very different ecosystems, and not a recent shift towards diurnality due to human disturbance.