Risky Business: The Function of Play in a Venomous Mammal-The Javan Slow Loris (Nycticebus javanicus).

Immature mammals require opportunities to develop skills that will affect their competitive abilities and reproductive success as adults. One way these benefits may be achieved is through play behavior. While skills in developing use of tusks, antlers, and other weapons mammals have been linked to play, play in venomous animals has rarely been studied. Javan slow lorises (Nycticebus javanicus) use venom to aid in intraspecific competition, yet whether individuals use any behavioral mechanisms to develop the ability to use venom remains unclear. From April 2012 to December 2020, we recorded 663 play events and studied the factors influencing the frequency of play and the postures used during play in wild Javan slow lorises. Regardless of the presence of siblings, two thirds of play partners of young slow lorises were older and more experienced adults. Young lorises engaged in riskier behaviors during play, including using more strenuous postures and playing more in riskier conditions with increased rain and moonlight. We found that play patterns in immature lorises bear resemblance to venom postures used by adults. We suggest that play functions to train immature lorises to deal with future unexpected events, such as random attacks, as seen in other mammalian taxa with weapons. Given the importance of venom use for highly territorial slow lorises throughout their adult lives and the similarities between venom and play postures, we cannot rule out the possibility that play also prepares animals for future venomous fights. We provide here a baseline for the further exploration of the development of this unique behavior in one of the few venomous mammals.

Growth and the development of sexual size dimorphism in lorises and galagos.

Three fundamental ontogenetic pathways lead to the development of size differences between males and females. Males and females may grow at the same rate for different durations (bimaturism), grow for the same duration at different rates, or grow at a mix of rate and duration differences. While patterns of growth and the development of adult body size are well established for many haplorhines, the extent to which rate and duration differences affect strepsirrhine growth trajectories remains unclear. Here, we present iterative piecewise regression models that describe the ontogeny of adult body mass for males and females of five lorisoid species (i.e., lorises and galagos) from the Duke Lemur Center. We test the hypotheses that, like most haplorhines, sexual size dimorphism (SSD) is a result of bimaturism, and males and females of monomorphic species grow at the same rate for a similar duration. We confirm that the galagos in this sample (Galago moholi and Otolemur garnettii) show significant SSD that is achieved through bimaturism. Unlike monomorphic lemurids, the lorises in this sample show a diversity of ontogenetic patterns. Loris tardigradus does follow a lemur-like trajectory to monomorphism but Nycticebuscoucang and Nycticebus pygmaeus achieve larger adult female body sizes through a mixture of rate and duration differences. We show that contrary to previous assumptions, there are patterns of both similarity and difference in growth trajectories of comparably sized lorises and galagos. Furthermore, when ontogenetic profiles of lorisoid and lemurid growth are compared, it is evident that lorisoids grow faster for a shorter period of time.

Exploring cultural drivers for wildlife trade via an ethnoprimatological approach: a case study of slender and slow lorises (Loris and Nycticebus) in South and Southeast Asia.

Illegal and unsustainable trade in wildlife is a major conservation challenge. For Asian primates, economic and cultural traditions, and increased forest access mean that trade may have become detrimental for certain species. Slow and slender lorises (Nycticebus and Loris) are primates particularly prevalent in trade, determined until now by focused counts of lorises in regional markets. Here, we use international trade statistics and a participant-observer approach to assess culturally specific drivers for trade in lorises in South and Southeast Asia, to provide a broader context to help mitigate this practice. Analysis of international records for the last 30 years revealed that live animal trade was more prevalent than trade in body parts (slow lorises, 86.4%; slender lorises, 91.4%), with Laos, Cambodia, and Thailand the largest exporters. We then examine drivers of international and domestic trade based on long-term data from 1994-2009 in Sri Lanka, Cambodia, and Indonesia. We show that slender lorises are important in Sri Lankan folklore, but their use as pets and for traditional medicine is rare. Trade in Bengal slow and pygmy lorises in Cambodia for use in traditional medicines, a practice with deeply historical roots, is widespread. Despite its own set of myths about the magical and curative properties of lorises, trade in Javan, Bornean, and greater slow lorises in Indonesia is largely for pets. Conservation practices in Asia are often generalized and linked with the region's major religions and economies. We show here that, in the case of wildlife trade, culturally specific patterns are evident among different ethnic groups, even within a country. Revealing such patterns is the foundation for developing conservation management plans for each species. We suggest some participatory methods for each country that may aid in this process.

Cranial ontogeny, diet, and ecogeographic variation in African lorises.

A series of 22 craniodental measurements were obtained for the three subspecies of potto (Perodicticus) and angwantibos (Arctocebus). To describe patterns of variation in Perodicticus, a discriminant function analysis (DFA) was performed with adult data. To investigate the ecogeographic correlates of size variation in Perodicticus, adult cranial dimensions were compared with field data on latitudinal and longitudinal coordinates for available specimens as well as altitudinal data for a more limited sample. Ontogenetic series for larger-bodied Perodicticus and smaller-bodied Arctocebus were compared to test the hypothesis that inter- and intrageneric variation in skull form results from the differential extension/truncation of shared patterns of relative growth, and to assess morphological variation in the masticatory complex of sister taxa with differing dietary habits. Analyses of relative growth indicate that skull proportions in Perodicticus subspecies are largely ontogenetically scaled. In comparisons between Perodicticus and Arctocebus, most facial dimensions also are ontogenetically scaled, with all but one of the seven divergent comparisons (interorbital breadth) representing a feature of the masticatory apparatus. The DFA provided independent support for prior classifications of Perodicticus into three taxa. Size differentiation in African lorises appears to be correlated with altitudinal variation (Bergmann's Rule) as well as character displacement. The smallest pottos, P. p. potto, occupy low-lying coastal habitats in western Africa, whereas the larger, eastern forms inhabit higher, presumably colder elevations. The largest potto, P. p. edwardsi, is sympatric throughout most of its range with the smallest and most insectivorous African lorises (Arctocebus). A basis for intrageneric taxonomic variation in Perodicticus is supported by such nonclinal size variation, as well as divergences in the ontogeny of masticatory proportions corresponding to interspecific variation in dietary proclivities.

Cranial allometry and geographic variation in slow lorises (Nycticebus)

A series of 20 craniodental measurements was obtained for two sister taxa: Nycticebus coucang (common slow loris) and N. pygmaeus (pygmy slow loris). Multivariate analysis of variance was performed with adult data to describe patterns of subspecific and specific variation in this genus. The geometric mean of adult cranial dimensions was compared to field data on latitudinal coordinates for available specimens to investigate if size variation in Nycticebus is clinal in nature. Ontogenetic series for larger-bodied N. coucang and smaller-bodied N. pygmaeus were compared to test the hypothesis that species and subspecific variation in skull form results from the differential extension of common patterns of relative growth. A MANOVA provides independent support of Groves's [pp. 44-53 in Proceedings of the Third International Congress on Primatology, Vol. 1 (Basel: S. Karger), in 1971)] classification of Nycticebus into two species, with four subspecies in the common slow loris and one form of the pygmy slow loris. Within N. coucang, cranial proportions for all four subspecies are ontogenetically scaled, and size differentiation is mainly clinal (Bergmann's Rule). N. c. bengalensis represents the most northerly disposed and the largest form. N. c. javanicus represents the next-largest form and is located in a southerly direction the next-farthest away from the equator. N. c. coucang and N. c. menagensis are both equatorial; however, the latter subspecies is the smallest. A genetic basis for some of the taxonomic variation between N. c. coucang and N. c. menagensis is supported by such nonclinal variation in body size. Variation in the presence/absence of I2 is not size-related but rather tracks geographic proximity and isolating factors which predate the most recent inundation of the Sunda Shelf. Although they inhabit a nonequatorial environment, pygmy slow lorises are the smallest of all Nycticebus. As N. pygmaeus is sympatric with N. c. bengalensis, the largest slow loris, it appears that the evolution of its smaller body size represents a case of character displacement. Unlike N. coucang, skull size becomes significantly smaller in more northern N. pygmaeus. This may also reflect character displacement between sympatric sister taxa underlain by a cline-dependent ecological factor which is marked in more northerly latitudes. On the other hand, the negative correlation between body size and latitude in N. pygmaeus could be due to the influence of nonprimate fauna, such as predators, which themselves evince a similar clinal pattern. Analyses of relative growth indicate that skull proportions in the two species of Nycticebus are ontogenetically scaled in two-thirds of the cases. All but one of the seven comparisons (interorbital breadth) which do not indicate ontogenetic scaling represent part of the masticatory complex. This likely reflects a reorganization of N. pygmaeus maxillomandibular proportions linked to smaller size and changes in diet.

Scaling of growth and life history traits relative to body size, brain size, and metabolic rate in lorises and galagos (Lorisidae, primates).

A broad range of variation in body size, brain size, and metabolic rate occurs within the primate family Lorisidae, thus providing an opportunity to examine the relationship of these three parameters to variation in growth and life history traits. Data on adult body weight, gestation length, lactation length, age at first estrus, litter size, and growth parameters were collected from a captive colony of four lorisid species, Loris tardigradus, Nycticebus coucang, Galago crassicaudatus, and G. senegalensis. The data presented here constitute the most complete life history information available for these poorly understood prosimian species. Correlation and allometric analyses were performed to determine the relationships between variables. Among the lorisids studied, adult body weight, adult cranial capacity, and relative cranial capacity did not predict variation in life history traits. Adult basal metabolic rate predicted most of the variability in gestation length, lactation length, and growth parameters. Lorisines differ from similarly sized galagines in having lower basal metabolic rates, slower growth rates, slower developmental rates, and smaller litter sizes, resulting in reduced reproductive potential. This may be a consequence of lorisine adaptation to a diet of toxic insects. Metabolic rate and diet may be among the most important parameters to examine in any study of life history evolution.