Northern Lesser Galago, Galago senegalensis
NORTHERN LESSER GALAGO
Geographic Distribution and Habitat
Northern lesser galagos are also known as lesser bushbabies, lesser galagos, Senegal galagos, and Senegal lesser galagos. Endemic to tropical Africa, they are perhaps the most widespread primate species on the continent. Their broad range includes Benin, Burkina Faso, Cameroon, Central African Republic, Chad, DR Congo, Côte d’Ivoire, Eritrea, Ethiopia, Gambia, Ghana, Guinea, Guinea-Bissau, Kenya, Mali, Niger, Nigeria, Rwanda, Senegal, Sierra Leone, Somalia, Sudan, Tanzania, Togo, and Uganda.
At home in a diverse variety of habitats, northern lesser galagos can be found in savanna woodland, dense to open bushland, montane forests, riverine woodland, and secondary and highly fragmented forest and woodland, including cultivated areas. They avoid areas of grassland. In central Kenya they are sympatric with the Somali lesser galago (Galago gallarum). They may be sympatric with southern lesser galagos (Galago moholi) in Tanzania.
There are four northern lesser galago subspecies:
- Kenya lesser galagos (Galago senegalensis braccatus) reside in a number of districts in Kenya. Their range extends southwards to northeast and north central Tanzania.
- Ethiopia lesser galagos (Galago s. dunni) are endemic to Somalia and the Ogaden region of Ethiopia.
- Senegal lesser galagos (Galago s. senegalensis) range from Senegal and the Gambia in the west through to Sudan, Uganda, and into western Kenya.
- Uganda lesser galagos (Galago s. sotikae) live in South Uganda and range to south of Lake Victoria, from Tanzania to southern Kenya, and southwards to northern, central, and possibly far-southern Tanzania.
Generally speaking, the exact boundaries of the northern lesser galago subspecies’ ranges are unclear.
Size, Weight, and Lifespan
In general, galagos are small. They weigh between 3 and 11 oz (95–300 g). Their body is 3.5–8 in (9–20.5 cm) long and their tail is 4–11 in (11–28 cm) long. Northern lesser galagos are in the middle of the range in both size and weight. Males are slightly larger than females.
They live 3 to 4 years in the wild, but can live up to 10 to 13 years in captivity.
To the untrained eye, all lesser galagos may look alike. These small busybabies have a long tail, large round eyes, big ears, elongated lower limbs with strong thigh muscles, short forelimbs, and a cute wet pointy nose. They have a brown or gray pelage, which keeps them camouflaged from predators. Their yellow or brown round eyes have reflective eye-shine and are perfectly adapted to night vision. They can turn their head 180 degrees, which gives them a broad field of vision. Their mobile ears allow them to track insects as they hunt. The round flat pads on their fingertips, between their fingers, and on their palms at the base of their thumbs provide them with a firm grip on the branches they leap to. Their pointed, keeled nails give them stability as they cling to smooth tree surfaces and reach for insects into crevices, using their rough narrow tongue. Their specialized ankle joints are responsible for the Olympian vertical leaps these galagos can perform, which can reach up to 7 feet (2 m) or more.
There are a few subtle yet unique physical traits marking lesser galago species. For example, the northern lesser galago’s gray and pinkish ears are larger than those of any other galagos. (And Somali lesser galagos have brown rings around their eyes.)
Northern lesser galagos are omnivorous, primarily feeding on tree gum, invertebrates, and fruit. They forage at all levels of the forest, on the ground or in the trees; however, when they share territory with larger galagos, they tend to remain in the lower canopy.
They capture insects with a rapid movement that is referred to as “smash and grab.” They swiftly extend their arm (usually the left) in the direction of their prey, grab it, and bring their hand to their mouth. They also eat fruit, like the bright red fruit of the jacket-plum tree and that of the sickle bush.
Individuals of all galago species and subspecies consume acacia gums leaking out of holes that beetles and moths make in the trees. There are two types of gum: the first is high in sugar and is a light yellow, almost transparent; the second is dark brown. Gums consist of carbohydrates and water. They are a good source of fiber, protein, calcium (ten times more so than insects or fruit), magnesium, and potassium. Gums are, therefore, essential to galagos’ survival in the cold season, when insects are scarce. They lick fresh gum spots on a tree. When it has hardened, they use their tooth-comb to scrape it off. The incisors on the lower front jaw of some animals are grouped as if to form a comb. The tooth-comb is used by these animals to groom and clean their fur or hair. Gums are difficult to digest, but the lesser galago’s stomach contains bacteria that is designed to break it down.
When food-deprived, galagos can become anemic and lose a lot of weight. They can even occasionally fall into a torpor (a sort of temporary hibernation that decreases physiological activity) to conserve energy. This state may only last a few hours but is sometimes repeated over several days.
Behavior and Lifestyle
Like all galagos, northern lesser galagos are nocturnal (active at night) and arboreal (tree-dwelling). They travel by leaping from tree to tree or hopping on the ground. They are vertical clingers and climb down trees the same way squirrels do—head first. Unlike other primates, they are rarely seen in large groups. They forage alone at night and regroup at sleeping sites at daybreak; however, when temperatures are cooler, galagos shorten their foraging activities by several hours and return to sleeping sites early. In such circumstances, they can be active during the day.
Galagos’ ears have four ridges and are very pliable. They can move each ear independently. The ability to bend and fold their ears enables them to zero in on prey in darkness as well as to locate the position of potential predators. They fold their ears back to protect them while leaping between thorny trees and bushes.
Galago groups are usually composed of 2–5 individuals. They forage separately.
Daytime is for resting. Males usually sleep alone. Females and offspring huddle together and sleep on open-top platforms of leaves in thorny trees, in the abandoned nests of birds, chimpanzees, or other galagos, or in tree hollows. These sleeping sites offer them some protection from predators and a escape. However, Somali lesser galagos uniquely do not use tree hollows as sleep sites.
Nighttime is when they come alive. They forage for food, meet their friends, play, inspect, and groom each other. Mothers and offspring stay close to one another. They can travel about 1.2 mi (2 km) to forage.
The territory of males is a bit larger than that of females and it overlaps the territory of one to five adult females. It is assumed that this practice enhances mating opportunities for the males.
When in danger, galagos’ first response is to run away, produce alarm calls, and, if necessary, bite and spit at their aggressor. Sleeping sites seem to be communal and groups may use a nest that another group used the day before. Galagos also like to visit each other’s sleeping areas and sniff around.
Lesser galagos coexist with larger galago species, monkeys, and apes wherever they live. They monitor their conspecifics (other lesser galagos) by sight, smell, and sound. Their home ranges sometimes overlap.
Galagos communicate in a variety of ways. They leave olfactory messages through secretions produced by glands on their face, chest, arms, elbows, palms, and soles. They use several vocalizations: the “quack” call can be heard for almost 0.2 mi (300 m). It is a territorial call, usually heard right after dusk and right before dawn. Calls are indicative of an individual’s location, sex, age, health condition, and intentions. Some calls are specific to males, others are shared by both genders. During mating season, individuals can utter advertising calls and leave scent marks.
Physical proximity to one another can indicate if galagos are friends or foes. They might plan their movements based on the calls they hear, moving toward the caller if they feel safe or engaging in counter-calling or defensive grunts if they are rivals. The pitch, rhythm, speed, and repeated patterns of the calls vary. These must be significant, but scientists have yet to determine their meaning.
They are called bushbabies for their calls that sound like crying human babies.
Males become dominant and sexually mature when they are almost a year old, at which time they move out of their natal group. They don’t go very far, about half a mile to a mile (1–2 km) away. Females become mature when they are 6 or 7 months old and go into estrus for up to three days.
Mating takes place in June, July, or September. Births coincide with the warm season, when food and shelter are easily found—October to early November and January to February. Females can breed twice a year. After a gestation period of 125–130 days, they usually give birth to a set of twins, each weighing no more than 0.7 oz (22 g). Moms carry their babies in their mouths for the first two weeks, until the infants are strong enough to hold onto their mother’s underside. The mothers forage alone but regularly return to the nest to nurse. Once the babies are old enough, the mothers park them in a tree nearby while they eat, and nursing becomes less frequent. Infants are weaned at about 10 weeks of age. Once weaned, the offspring initiate most of the contact with their mother; they groom their mothers, who often do not reciprocate. Males are not involved at all in the rearing of their progeny.
Juveniles forage alone and gradually increase the distance they travel to find food. They engage in play fighting, with males rough housing more than females. Mothers keep an eye on them and prevent other females and juveniles from entering their territories by scent marking, calling, and fighting if necessary. When daughters mature, they leave their mothers’ territory for their own.
No specific information is known about the ecological role of lesser galagos. It is likely that they are seed dispersers in their habitats.
The International Union for Conservation of Nature lists the northern lesser galago as Least Concern, appearing on Red List of Threatened Species (IUCN, 2016). They are widespread and locally abundant. Although they are affected by habitat loss in some parts of their geographical range, there are no major range-wide threats to the species.
The northern lesser galago is able to survive in habitats marginally affected by humans and near human settlements. Local population declines are occurring due to habitat loss from clear-cutting and intensive agriculture related to fast-growing human populations in its geographic range.
Their main predators are large snakes, jackals, mongooses, genets, wild cats, raptors, small carnivores, and owls. Chimpanzees have been observed hunting the sleeping galalgos with spears in tree hollows. Humans are another threat. Galagos are killed and sold as bushmeat or for their organs, which are believed to have traditional medicinal properties. Some are also captured for the illegal pet trade.
The Northern lesser galago, galago senegalensis, is listed on Appendix II of the Convention on International Trade in Endangered Species (CITES). They occur in a large number of protected areas throughout the range including Tsavo West National Park, Tsavo East National Park, Mt. Kenya National Park, Meru National Park, Kora National Park, Samburu National Reserve, Shaba National Reserve, Buffalo Springs National Reserve in Kenya; in Tanzania, in Grumeti Game Reserve, Serengeti National Park, Lake Manyara National Park, Tarangire National Park and Mikumi National Park; in Uganda, in Kidepo Valley National Park, Otzi Forest Reserve, Agoro-Agu National Reserve; and in the Gambia, in Niumi National Park.
- Primates – The Amazing World of Lemurs, Monkeys, and Apes – Barbara Sleeper
- Primate Societies – Lorises, Bushbabies, and Tarsiers: Diverse Societies in Solitary Foragers – Simon K. Bearder
- Life in the Thornbush – the Somali Bushbaby – Yvonne A. De Jong
- Species-Typical Patters of infant Contact, Sleeping Site Use and Social Cohesion among Nocturnal Primates in Africa – Simon K. Bearder, Lesley Ambrose, Caroline Harcourt, Paul Honess, Andrew Perkin, Elizabeth Pimley, Samantha Pullen, Nadine Svoboda.
- International Journal of Primatology Vol. 1, No. 2, 1980 – Acacia Gum and Its Use by Bushbabies, Galago senegalensis – S.K. Bearder and R. D.Martin
- Primates of Mahale Mountains National Park, Tanzania – Thomas M. Butynski, Yvonne A. de Jong.
- African Primates 7 (1): 42-49 (2010) – Grandmothering in Galago senegalensis braccatus (Senegal Galago) – Sharon E. Kessler & Leanne T. Nash
- Intraspecific Variation in the Vocalizations and Hand Pad Morphology of Southern Lesser Bush Babies (Galago moholi): A Comparision with G. Senegalensis – M.J.Anderson, L.Ambrose, S.K. Bearder, A. F. Dixson, and S.Pullen
- International Journal of Comparative Psychology, Vol. 11, No.4, 1998 – Left Hand Advantage for Prey Capture in the Galago (Galago Moholi) – Jeannette P. Ward. University of Memphis, USA.
- International Journal of Primatology (2013) 34:49-64 – Surviving the Cold, Dry Period in Africa: Behavioral Adjustments as an Alternative to Heterothermy in the African Lesser Bushbaby (Galago moholi) – Julia Nowack, Martha Wippich, Nomakwezi Mzilikazi, Kathrin H. Dausmann
- African Primates 11(1): 45-48 (2016) – Brief Communication: Documentation of Plant Consumption by Galago moholi in South Africa – Ian Ray, Brandi T. Wren, Evelyn J. Bowers
- Journal of East African Natural History 93: 23-38 (2004) – Natural History of the Somali Lesser Galago (galgo gallarum) – Thomas M. Butynski, Yvonne A. de Jong
- Folia Primatologica 2003; 74:285-300 – Sex Differences in the Behavior and the Social Interactions of Immature Galago senegalensis braccatus – Leanne T. Nash – Arizona State University
- International Journal of Primatology Vol. 10, No. 1, 1989 – Synopsis of Galago Species Characteristics – Leanne T. Nash, Simon K. Bearder, Todd R. Olson
- Galago moholi – The Red List of Mammals of South Africa, Lesotho and Swaziland
- IUCN Red List of Threatened Species, Northern Lesser Galago
Written by Sylvie Abrams and Debra Curtin, December 2020