Simon K. Bearder

Fission-Fusion Dynamics: New Research Frameworks

Renewed interest in fission‐fusion dynamics is due to the recognition that such dynamics may create unique challenges for social interaction and distinctive selective pressures acting on underlying communicative and cognitive abilities. New frameworks for integrating current knowledge on fission‐fusion dynamics emerge from a fundamental rethinking of the term “fission‐fusion” away from its current general use as a label for a particular modal type of social system (i.e., “fission‐fusion societies”). Specifically, because the degree of spatial and temporal cohesion of group members varies both within and across taxa, any social system can be described in terms of the extent to which it expresses fission‐fusion dynamics. This perspective has implications for socioecology, communication, cognitive demands, and human social evolution.

Assessment of the diversity of African primates

This account of the systematics of African primates is the consensus view of a group of authors who attended the Workshop of the IUCN/SSC Primate Specialist Group held at Orlando, Florida, in February 2000. We list all species and subspecies that we consider to be valid, together with a selected synonymy for all names that have been controversial in recent years or that have been considered to be valid by other authors in recent publications. For genera, species-groups or species, we tabulate and discuss different published systematic interpretations, with emphasis on more recent publications. We explain why we have adopted our taxonomic treatment and give particular attention to cases where more research is urgently required and in which systematic changes are most likely to be made. For all taxa, from suborder to subspecies, we provide English names.

Acacia gum and its use by bushbabies, Galago senegalensis (Primates : Lorisidae)

Lesser bushbabies (Galago senegalensis moholi)were studied by radiotracking over a 2-year period (August 1975 to August 1977)at a thornveld study site in the Northern Transvaal, South Africa. It was confirmed that the diet consisted exclusively of plant exudates (gums) and arthropods;available fruits were never eaten. The gums were taken from the trunks and branches of Acaciatrees, particularly from Acacia karroo(the major source), from A. tortilis,and to a small extent from A. nilotica.Chemical analysis shows that gums consist predominantly of carbohydrates and water, with small quantities of fiber, protein, and minerals (notably calcium, magnesium, and potassium). Thus, the gums probably present first and foremost a source of carbohydrate in the diet of the lesser bushbaby, though it seems likely that special mechanisms must exist for digestion of the polymerized pentose and hexose sugars. The calcium content of the gums (approx. 1% by weight) is probably significant in offsetting the low calcium content of the arthropod prey, and their high calcium:phosphorus ratio may well counterbalance the low calcium:phosphorus ratio of the arthropods. The gums are apparently produced largely in response to insect activity. Larvae of beetles (families Cerambycidae,Buprestidae, and Elateridae) and of moths (family Coccidae) bore channels beneath the tree surface, and gum is liberated through apertures made during invasion of the host Acacia.Fly larvae (family Odiniidae) may also develop in the gumfilled cavities. Gum exuding onto the surface is collected by the bushbabies on regular nightly visits, and firm evidence was obtained, in the form of characteristic marks on trap baseboards and certain gum sites, that the toothscraper in the lower jaw is used to scoop away gum from tree surfaces. Foraging for, and feeding upon, gum increased during the winter months, which may be particularly harsh in certain years. In the especially cold winter covered by the study, insect availability was minimal and the lesser bushbabies fed mainly on gum, with some of them reducing their total activity period during the night. Gums are available throughout the year and detailed records indicated no clearcut seasonal pattern of gum production. They are therefore an important yearround food resource for the lesser bushbabies. Feeding on gums has been reported for a wide range of primate species in recent years (especially for various species of the families Cheirogaleidae, Lorisidae, and Callitrichidae), and these plant exudates must now be regarded as an important dietary category within the order Primates.

Synopsis of Galago species characteristics

At the time of the symposium, “Variability Within the Galagos,” at the 1986 IPS Congress, most participants were still using Hill’s (1953) classification and nomenclature of galago species. All participants expressed some degree of dissatisfaction with Hill’s species groups. Many described how it was proving increasingly problematic and inadequate as a means to organize newly collected laboratory, museum, and field data. By the end of the symposium, a consensus about species diversity had emerged which synthesized the current state of knowledge about galagos. The consensus of the participants was that the 11 species, identified by Olson (1979, 1986), most closely approximates the available data about galago species diversity. The 11 species are described.

Physical and social diversity among nocturnal primates: A new view based on long term research

Social complexity is not restricted to day-living primates. Nocturnal primates provide a remarkably diverse, and largely overlooked, array of species for comparison with the better known monkeys, apes, and diurnal lemurs. Nocturnal and diurnal species differ markedly in terms of their sensory and perceptual abilities, but they share a high relative brain size in association with long periods of gestation, development of the young, and lifespan. Both groups also show within- and between-species diversity in their systems of feeding, defence, and reproduction, mediated by remarkably complex channels of communication, and varying locally in relation to habitat, demography, and social tradition. This paper provides a broad overview of the physical and social diversity of nocturnal primates, leading to new perspectives on their speciation, social behaviour and conservation status.

The Social Organization of a Nocturnal Primate Revealed by Radio Tracking

Abstract During a two year field study in South Africa, all members of a community of lesser bushbabies (Galago senegalensis moholi) within a 1 × 1 km study area were captured, individually marked, and recaptured at regular intervals. Daily sightings of radio tagged animals at their sleeping sites offered a reliable basis for mapping individual home ranges. An analysis of social contact and dispersal during this relatively gregarious phase of the daily activity cycle is supplemented by quantitative data from direct observation at night with the aid of red light, including 57 nights on which single bushbabies were followed throughout the active period. A basic system of male and female territoriality between well established individuals of the same sex is obscured by a complex pattern of ranging and social contact exhibited by lower ranking animals. Periodic ‘mating’ and ‘removal’ migrations are described briefly. Despite the predominantly solitary habits of this species, social interrelationships are similar to those found within ‘age-graded male’ groups of more gregarious primates.

Species Diversity Among Galagos with Special Reference to Mate Recognition

This paper argues that the number of species of nocturnal primates has been seriously underestimated. It has been traditional to separate species largely on the basis of the physical characteristics of museum specimens. This is satisfactory when the animals’ themselves recognize one another by sight, as in the majority of birds and day-living primates, but where scent and sound play the predominant role in male-female recognition, species boundaries can easily be overlooked. As Tinbergen has pointed out, closely related species do not ordinarily interbreed because: ‘the various signals serving attraction, persuasion, appeasement, and synchronisation, are so very different from one species to another.’ (Tinbergen, 1953, p.36). Here we use one conspicuous element in the communication system of galagos, which are all nocturnal, to demonstrate that similarlooking populations frequently belong to different species which have yet to be investigated.

A Re-Evaluation of the Role of Vision in the Activity and Communication of Nocturnal Primates

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.

Variations in Vocal Patterns of Senegal and South African Lesser Bushbabies and Their Implications for Taxonomic Relationships

Vocalizations of Senegal and South African lesser bushbabies were compared with respect to their acoustic properties analysed from spectrograms and oscillograms. Homologous calls could be identified within comparable functional categories. Considerable similarities were revealed in most of the noisy vocalizations associated with aggressive, defensive or anxiety and alarm behaviour. Striking divergences were detected, however, in almost all of the tonal or harmonic call types given in association with contact or contact-seeking, defensive or alarm behaviour. The results provide strong support for the separation of the two forms into distinct species, Galago senegalensis and Galago moholi.

Preliminary observations on sexual behavior and the mating system in free-ranging lesser galagos. (Galago moholi).

Sexual and associated patterns of behavior of lesser galagos (Galago moholi) were recorded during an 18‐month study conducted at the Nylsvley Nature Reserve in South Africa. Animals were trapped and fitted with radio transmitter belts in order to monitor nocturnal activities during twice‐yearly mating seasons. Most copulations occurred during the last week in May, while a subsidiary (post‐partum) mating season occurred in late September–early October. Females came into estrus sequentially during the May season. Adult males exhibited increase in body weight and testes volume during the mating season, changes which were most pronounced among the larger males (> 226g). Larger males also had the greatest mating success, initiating 88% of observed copulations. Sixty‐seven percent of matings involved more than one male copulating with the same female during her estrus, which lasted 1–3 days. Mounts were prolonged (range 2–53 min, mean 9.0 min) and males copulated repeatedly (2–5 times) with the same partner during a single night. These observations of sexual behavior and of large relative testes size in free‐ranging lesser galagos are consistent with the occurrence of a dispersed mating system involving sperm competition in this nocturnal prosimian species. Am. J. Primatol. 51:79–88, 2000.