Bushbabies

(Galagidae)

Class: Mammalia

Order: Primates

Family: Galagidae

Thumbnail description
Relatively small mammals with a long, often bushy tail; fur coloration varies from gray to black dorsally and from white to orange-buff ventrally; eyes large and oriented obliquely forwards; ears membranous and moderate to large; hindlimbs markedly longer than forelimbs; all digits of the hand and foot bear nails

Size
Relatively small body size, ranging from Demidoff's bushbaby (head and body length: 5 in [13 cm]; tail length: 7 in [18 cm]); body mass: males 2.5 oz [65 g]; females 2 oz [55 g]) to the Brown greater bushbaby (head and body length: 12.5 in [31.5 cm]; tail length: 16.5 in [41 cm]; body mass: males 2 1b 10 oz [1,190 g]; females 2 1b 7 oz [1,110 g])

Number of genera, species
4 genera; 20 species

Habitat
Inhabit a wide spectrum of forest and woodland types, from dry, thorny scrub to evergreen tropical rainforest

Conservation status
Endangered: 1 species; Lower Risk/Near Threatened: 6 species; Data Deficient: 2 species

Distribution
Widespread occurrence throughout Africa

Evolution and systematics

For several decades, all bushbaby (or galago) species were generally allocated to the single genus Galago, but it was eventually recognized that there are major differences between the species and up to 4 different genera are now recognized (Euoticus, Galago, Galagoides, and Otolemur). Molecular evidence indicates that divergence between these four genera took place at a very early stage, although the relationships between them have not been clearly established.

Together with the lorises (subfamily Lorisinae) and pottos (subfamily Perodictinae) in the family Lorisidae, the bush-babies constitute the monophyletic infraorder Lorisiformes, which is the sister group of the Lemuriformes (Malagasy lemurs). The Lorisiformes and the Lemuriformes together form a monophyletic assemblage of strepsirrhine primates, which are characterized by retention of the rhinarium (a moist area of naked skin surrounding the nostrils), by non-invasive epitheliochorial placentation and by possession of a tooth-comb containing four incisors and two canines in the lower jaw as a derived, diagnostic feature. The bushbabies (family Galagidae) almost certainly belong to a monophyletic assemblage, but the relationships between bushbabies, lorises and pottos remain unclear.

For many years, the fossil record for bushbabies was limited to two early Miocene genera from East Africa (Komba and Progalago). These Miocene forms have now been supplemented by isolated teeth from late Eocene deposits in Egypt, showing resemblances to modern bushbabies and allocated to the genus Saharagalago. Thus, fossil evidence indicates that the families Lorisidae and Galagidae have existed as separate lineages for at least 38 million years.

It was proposed, on technical grounds of priority, that the family name "Galagidae" be changed to "Galagonidae." Because the usual name "Galagidae" has been in widespread use for a very long time, however, the International Committee on Zoological Nomenclature retained the name officially.

Physical characteristics

Bushbabies are relatively small mammals. The tail, which is often bushy, is always long in comparison to the body and is actively used in locomotion. According to species, fur coloration ranges from gray to black dorsally and from white to orange-buff ventrally. The eyes are relatively large and oriented obliquely forwards. The ears, which are membranous and moderate to large in size, can be folded concertina-fashion. In the skull, there is a bony strut (postorbital bar) on the outer margin of the eye socket. The dental formula is (I2/2 C1/1 P3/3 M3/3) 2 36 total teeth. In the lower jaw, the crowns of the four incisors (two on each side) and the two canines (one on each side) are angled forwards to form a dental comb that is used both for feeding and for grooming the fur. The hindlimbs are markedly longer than the forelimbs. All digits of the hand and foot bear nails, although the second toe bears an elongated nail ("grooming claw") that is angled away from the dorsal surface. Mild sexual dimorphism in body size is present in some bushbabies but absent in others.

Distribution

Bushbabies occur exclusively in Africa, but have a very wide distribution on that continent.

Habitat

Bushbabies are found in a wide variety of habitats, ranging from dry, thorny scrub to evergreen tropical rainforests. There is a fairly clear separation between species that occur in evergreen rainforests and those that live in dry deciduous forests.

Behavior

All bushbabies are typically arboreal and nocturnal. They have a reflecting layer (tapetum lucidum) behind the retina. It has been shown for the thick-tailed bushbaby (Otolemur crassicaudatus) that flat crystals of riboflavin are responsible for the reflecting properties of the tapetum and the resulting golden yellow eyeshine. Although all bushbaby species have relatively long hindlimbs, with conspicuous elongation of the calcaneum and navicular in the ankle region, there is considerable variation in their patterns of locomotion. Most species are active leapers, but only some of them are specialized vertical-clingers and leapers that can jump several meters between supports and show bipedal hopping along broad horizontal branches and on the ground (e.g., Galago alleni and Galago moholi). Many species are primarily quadrupedal (e.g., Galagoides demidoff and Otolemur garnettii), and some (e.g., Otolemur crassicaudatus) leap relatively rarely. All species show scent marking of some kind and most if not all show the unusual pattern of "urine washing" in which the palms of the hands and the soles of the feet are impregnated with urine, such that urine traces are deposited on the substrate during locomotion. Although most of them are solitary foragers, all bushbabies live in social networks of some kind, involving occasional encounters within overlapping ranges of adult males and females and sharing of nest sites during the daytime. Species differ in features such as the number of individuals in a social network, the amount of contact shown during nocturnal activity, the degree of tolerance among adults and subadults of the same sex, and the stability of nesting groups.

Feeding ecology and diet

The basic diet of most bushbaby species is a mixture of fruit and arthropods (mainly insects), although small vertebrates, eggs, gum and other items may also be eaten. The proportions of arthropods and fruits in the diet vary from species to species. Small-bodied species tend to be more insectivorous, while large-bodied species tend to be more frugivorous. Some bushbaby species include quite large amounts of gum in their diets, and the needle-clawed bushbabies (e.g., Euoticus species) are specialized gum-feeders, feeding predominantly on that resource.

Reproductive biology

Bushbabies are polygynous. Most species give birth to a single infant, but some regularly produce twins, and triplets can also occur. All species have non-invasive epitheliochorial placentation. Average gestation period lasts between 112 and 136 days according to species. All species show maternal carriage of the infant(s), usually in the mouth but in certain cases (e.g., Otolemur crassicaudatus) also clinging to the mother's fur.

Conservation status

Most species are thought to be relatively common. One species is endangered (Galago rondoensis) and six are Near Threatened (Euoticus elegantulus, Euoticus pallidus, Galago alleni, Galago gallarum, Galago matschiei, and Galago zanzibaricus). Two species are listed as Data Deficient (Galago granti and Galago orinus).

Significance to humans

Bushbabies seem to be of no real significance to local human populations, although the larger-bodied species may occasionally be eaten.

Species accounts

Resources

Alterman, Lon, Gerald A. Doyle, and M. Kay Izard, eds. Creatures of the Dark: The Nocturnal Prosimians. New York: Plenum Press, 1995.

Bearder, Simon K. "Lorises, Bushbabies, and Tarsiers: Diverse Societies in Solitary Foragers." In Primate Societies, edited by Barbara B. Smuts, Dorothy Cheney, Robert M. Seyfarth, Richard Wrangham, and Thomas Struhsaker. Chicago: Chicago University Press, 1987, 11–24.

Bearder, Simon K., and R. D. Martin. "The Social Organization of a Nocturnal Primate Revealed by Radio-tracking." In A Handbook on Biotelemetry and Radio Tracking, edited by Charles J. Amlaner and David W. Macdonald. Oxford: Pergamon Press, 1980, 633–648.

Charles-Dominique, Pierre. Ecology and Behaviour of Nocturnal Primates. London: Duckworth, 1977.

Groves, Colin P. Primate Taxonomy. Washington, DC: Smithsonian Institution, 2001.

Jenkins, Paula D. Catalogue of Primates in the British Museum (Natural History) and Elsewhere in the British Isles. Part IV: Suborder Strepsirrhini, Including the Subfossil Madagascar Lemurs and Family Tarsiidae. London: British Museum (Natural History), 1987.

Martin, Robert D. Primate Origins and Evolution: A Phylogenetic Reconstruction. Princeton, NJ: Princeton University Press, 1990.

Sussman, Robert W. Primate Ecology and Social Structure. Volume 1. Lorises, Lemurs and Tarsiers. Needham Heights, MA: Pearson Custom Publishing, 1999.

Anderson, Matthew J. "Comparative Morphology and Speciation in Galagos." Folia Primatology 69 Suppl. (1998): 325–331.

Bearder, S. K., and R. D. Martin. "Acacia Gum and its use by Bushbabies, Galago senegalensis (Primates: Lorisidae)." International Journal of Primatology 1 (1980): 103–128.

Butler, Harold. "The Reproductive Biology of a Strepsirhine (Galago senegalensis senegalensis)." International Review of Genetics and Experimental Zoology 1 (1964): 241–296.

Charles-Dominique, Pierre. "Urine Marking and Territoriality in Galago alleni (Waterhouse 1837—Lorisoidea, Primates): A Field Study by Radio-telemetry." Zeitschrift fuer Tierpsychologie 43 (1977): 113–138.

Charles-Dominique, P., and R. D. Martin. "Evolution of Lorises and Lemurs." Nature 227 (1970): 257–260.

Clark, Anne B. "Sociality in a Nocturnal 'Solitary' Prosimian: Galago crassicaudatus." International Journal of Primatology 6 (1985): 581–600.

Crovella, S., J. C. Masters, and Y. Rumpler. "Highly Repeated DNA Sequences as Phylogenetic Markers Among the Galaginae." American Journal of Primatology 32 (1994): 177–185. de Boer, L. E. M. "Cytotaxonomy of the Lorisoidea (Primates: Prosimii). I: Chromosome Studies and Karyological Relationships in the Galagidae." Genetica 44 (1973): 155–193.

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Size and Perinatal Behaviour of Females." Journal of Zoology, London 210 (1986): 451–457.

Harcourt, C. S., and L. T. Nash. "Social Organization of Galagos in Kenyan Coastal Forests. I. Galago zanzibaricus." American Journal of Primatology 10 (1986): 339–355. ——. "Species Differences in Substrate use and Diet Between Sympatric Galagos in Two Kenyan Coastal Forests." Primates 27 (1986): 41–52.

Izard, M. Kay. "Lactation Length in Three Species of Galago." American Journal of Primatology 13 (1987): 73–76.

King, B. F. "The Fine Structure of the Placenta and Chorionic Vesicles of the Bush Baby, Galago crassicaudatus." American Journal of Anatomy 169 (1984): 101–116.

Masters, J. C. "Speciation in the Lesser Galagos." Folia Primatology 69, Suppl. (1998): 357–370.

Nash, L. T. "Galagos and Gummivory." Human Evolution 4 (1989): 199–206.

Nash, L. T., S. K. Bearder, and T. R. Olson. "Synopsis of Galago Species Characteristics." International Journal of Primatology 10 (1989): 57–79.

Nash, L. T., and C. S. Harcourt. "Social Organization of Galagos in Kenyan Coastal Forests: II. Galago garnettii." American Journal of Primatology 10 (1986): 357–369.

Pullen, S. L., S. K. Bearder, and A. F. Dixson. "Preliminary Observations on Sexual Behavior and the Mating System in Free-ranging Lesser Galagos (Galago moholi)." American Journal of Primatology 51 (2000): 79–88.

Rasmussen, D. T., and K. A. I. Nekaris. "Evolutionary History of Lorisiform Primates." Folia Primatology 69, Suppl. (1998): 250–285.

Schwarz, E. "On the African Long-tailed Lemurs or Galagos." Annual Magazine of Natural History ser. 10, 7 (1931): 41–66.

Schwartz, J. H., et al. "LORISIDAE Gray, 1821 and GALAGIDAE Gray, 1825 (Mammalia, Primates): Proposed Conservation as the Correct Original Spellings." Bulletin of Zoology Nomenclature 55 (1998): 165–168.

Smith, R. J., and W. L. Jungers. "Body Mass in Comparative Primatology." Journal of Human Evolution 32 (1997): 523–559.

Wickings, E. J., L. Ambrose, and S. K. Bearder. "Sympatric Populations of Galagoides demidoff and Galagoides thomasi in the Haut-Ogooué Region of Gabon." Folia Primatology 69, Suppl. (1998): 389–393.

Zimmermann, Elke. "Aspects of Reproduction, Behavioral and Vocal Development in Senegal Bushbabies (Galago senegalensis)." International Journal of Primatology 10 (1989): 1–16. ——. "Differentiation of Vocalizations in Bushbabies (Galaginae, Prosimiae, Primates) and the Significance for Assessing Phylogenetic Relationships." Zeitschrift fuer Zoologische und Systemische Evolution Forschung 28 (1990): 217–239.

[Article by: Robert D. Martin, PhD]