Allen’s Squirrel Galago, Sciurocheirus alleni
ALLEN’S SQUIRREL GALAGO
Sciurocheirus alleni
Geographic Distribution and Habitat
Allen’s squirrel galagos (Sciurocheirus alleni), also known as Allen’s galago or Allen’s bushbaby, are found in West Africa, specifically southeast Nigeria, southwest Cameroon, and a subspecies is found on the island of Bioko. They prefer primary rainforest habitats and can be found at altitudes ranging from sea level to 7,380 feet (2,250 m). Depending on human activity, some groups may be found in secondary forests and farm bushes. Within the forest, they prefer to reside either closer to the ground, in the undergrowth, or in the mid-canopy with vertical supports to aid in clinging and leaping.
TAXONOMIC NOTES
Depending upon the source, three or four species are recognized in the genus Sciurocheirus:
- The Allen’s squirrel galago (Sciurocheirus alleni)
- The Makande squirrel galago (Sciurocheirus makandensis)
- The Gabon squirrel galago (Sciurocheirus gabonensis)
- The Cross River squirrel galago (Sciurocheirus cameronnensis): a species smaller than the Allen’s squirrel galago, it has been identified north of the Sanaga River in southwest Cameroon and Nigeria. However, some sources consider this to be a subspecies of Allen’s squirrel galago rather than a full species.
Another subspecies of the Allen’s squirrel galago (Sciurocheirus alleni), known as the Bioko squirrel galago (Sciurocheirus alleni alleni), is endemic to the Bioko Island (Equatorial Guinea).
Size, Weight, and Lifespan
On average, both males and females weigh between 7 and 16 lbs (200–455 g). The head-to-body length ranges between 6 and 9 inches (15.5–24.0 cm), and tail length between 8 and 12 inches (20.5–30.0 cm).
Although some reports suggest that these animals live up to 12 years in captivity, individuals have lived up to 8 years in the wild.
Appearance
Allen’s squirrel galagos are covered with a fluffy fur throughout their body, except for the nose and digits on their hands and feet. The fur is grayish brown on the back and lighter on the underbelly, with an orangey tint on the limbs. The eyes are relatively large for the face and oriented forward, framing a pointed little nose. The tail is long and bushy. Galagos have large naked ears that are mobile and can be folded or moved backward. The hindlimbs are longer than the forelimbs and help with leaping.
Diet
Allen’s squirrel galagos are categorized as omnivores and eat both fruits and insects; however, their diet varies considerably across sites as well as seasonally. In the primary forests, where more fruit can be found, Allen’s squirrel galagos eat 75% fruit, 25% animal matter, and some gums; however, in the secondary forests they consume a higher proportion of insects. Animal matter can consist of beetles, snails, moths, frogs, spiders, etc. Since Allen’s squirrel galagos prefer to stay in the undergrowth, they usually feed on fruits fallen on the ground and are reported to eat rapidly and even swallow fruits whole, allowing them to fill their stomachs within minutes while they retreat to areas safer from potential predators.
Arboreal (tree-dwelling), Allen’s galagos locomote almost exclusively by leaping, like tree-frogs, between vertical supports in the undergrowth and between small trees and the ground. They can leap between vertical supports as much as 8 feet (2.5 m) away from one another in a matter of seconds, which is nearly 14 times their body length (excluding tail). In fact, their movement is so rapid that photographs have shown that only half a second elapses between the moment of landing on a plant trunk and the instant of take-off again. When on the ground, they can employ a rapid standing high jump, where they leap back to a trunk or vine at the slightest provocation.
These rapid leaps on vertical supports through the undergrowth are due to numerous adaptions. For example, while landing, they land hands first, unlike other galagos, which land feet first or with all limbs simultaneously. The forelimbs play a role in absorbing the landing impact, but most of the speed is due to the hind limbs. After landing, they control their angle of rotation to follow a specific path by pivoting around the vertical support and simultaneously rotating their head to 180º relative to the body before leaping again.
Allen’s squirrel galagos are nocturnal and rest during the day; however, if disturbed during the day, they may leave their nests and move deeper into the forest. Since their fur is easily soaked by rain, Allen’s squirrel galagos use natural holes in trees while sleeping, but they do not necessarily build nests. When not using tree holes, they shelter in dense tangles of vegetation and may rarely even hide in holes at the foot of trees, covered by leaves. Two to four individuals sleep together at the same nesting site. Males generally sleep individually whereas females sleep with 2–3 other adult females and their offspring together in the same site.
Allen’s galagos are able to make vertical leaps of 8 feet (2.5 m), which is nearly 14 times their body length (excluding tail).
Females “park” their infants in nearby undergrowth while foraging and retrieve their kids when done with the meal.
Energetic males may rendezvous with as many as 5 females in a single night.
Once it starts becoming dark, Allen’s squirrel galagos leap out of their holes and head for fruit trees. While they are nocturnal, they take short rests dispersed through the night with resting periods ranging from 15 minutes to 2 hours, usually when they have full stomachs.
Not huge fans of getting wet, they retreat to the nearest patch of dense foliage to protect their fur from getting drenched during heavy rainfall; however, during light rain showers, they continue to move around and feed.
After waking up and before emerging from the tree-hole sleeping sites, they either extensively groom themselves or partake in social grooming. The mother frequently licks her offspring and, even after the adult stage is reached, allogrooming remains a frequent activity among individuals belonging to the same social group. Allogrooming is social mutual grooming within a species.
Allen’s squirrel galagos emit different calls for different situations. Infants emit short “clicks” in the morning during sunrise. If the mother does not come to collect the vocalizing infant, the clicks become increasingly concentrated and transform into frustrated “tsic” calls. The infant will also emit the “tsic” call when it is trying to find a more comfortable position by the mother’s body or wants to feed.
To establish long-distance contact, individuals in a group emit low-pitched “croaks” to communicate with others. Mothers may also emit croaks to establish contact with their infants. Croaks are also produced when males and females want to find each other in order to copulate. A second type of social contact called “mew whistles,” also known as cohesion mew whistles, are emitted to coordinate movement between two or three individuals that are within close range during activities, such as when foraging together. These calls are also emitted when the animals leave their sleeping sites and at intervals throughout the night to maintain group cohesion.
Alarm calls that sound like “kiou-kiou” are elicited when any disturbance in the surroundings is detected, such as when they hear an unusual sound or detect a predator. Threat calls, “quee quee,” are uttered toward other individuals asking for them to retreat and avoid contact. These calls are produced with the mouth open and are associated with a hunched aggressive posture. Distress calls, “wheet,” are uttered by individuals following an injury or when they are restrained. For example, during a fight, if one of the members emits a distress call, the other will release its hold.
In addition to vocal signals, non-vocal signals are also used to communicate. Urine washing is performed, wherein the individuals urinate on the inner surfaces of their feet and hands and then touch the supports—sometimes they pee directly on the supports. By depositing urine throughout their home range, the galagos establish territories and indicate their identity to other individuals.
Males visit females at night and sometimes multiple females in the same night. These visits are brief and usually involve allogrooming. However, if one of the females comes into estrus, the male will not leave her for several days. Both males and females attain sexual maturity at around 8 to 10 months of age. Births can occur year-round, and the average gestation length is 133 days. Females typically give birth to a single infant (rarely 2) per year.
Three to seven days after birth, the mother begins to carry her infant out of the tree hollow at dusk and “parks” the baby in the undergrowth, where the infant remains immobile. Infant parking is a practice in which the mother leaves her infant on a branch or in a tree hole while she goes off to forage. While the baby is parked, the mother feeds in the vicinity. If she moves to feed in another area, she collects the infant and redeposits the baby in the vegetation close by. As dawn approaches, she will collect the infant and carry it back to the nesting site. After 2–3 weeks, the infant begins to move around independently and wanders around the nesting site or the park site. The female carries the young in her mouth for up to 6 weeks when going out to forage.
Due to their frugivory diet, Allen’s squirrel galagos transport fruit seeds, thus playing a role in seed dispersal for plant species over varying distances. While consuming insects and other small animals, these monkeys also control the populations of insects and small animals. In addition, as a prey species, Allen’s squirrel galagos may have a positive impact on the populations of its predators.
The International Union for Conservation of Nature lists the Allen’s squirrel galago, Sciurocheirus alleni, as Near Threatened (IUCN, 2017), appearing on the IUCN Red List of Threatened Species.
Due to a growing human population, more sophisticated hunting technologies, and increasing human access to isolated forest areas, these primates are facing threats such as habitat loss and the exotic pet trade. Habitat loss due to large-scale agricultural projects for oil palm plantation and crops, in addition to urbanization, are leading to forest loss and declining populations. Allen’s squirrel galagos are subjected to international trade in which they are caught in the wild and exported out of their African range countries to be sold as pets. There are also reports of them being hunted to be sold as bushmeat along roadsides.
Natural threats include predation by mongooses, jackals, raptors, and venomous snakes.
The Allen’s squirrel galago (Sciurocheirus alleni) is listed in Appendix II of the Convention on International Trade in Endangered Species (CITES), an international agreement between governments whose goal is to ensure that international trade in specimens of wild animals and plants does not threaten their survival.
Allen’s squirrel galagos occur in national parks, wildlife sanctuaries, and scientific reserves in Cameroon, Nigeria, and Bioko that are considered protected.
While the galagos occur in so-called protected areas, they still succumb to illegal trades across country borders. The countries where galagos occur have laws in place to prevent, detect, and penalize illegal trade; however, these laws are often outdated and not enforced. Additionally, local communities in many developing African countries depend heavily on wild animals. In order to ensure conservation of this species, countries must update and enforce local legislations and curb international trade by using CITES efficiently and effectively.
- Bearder, S. K.; Ambrose, L.; Harcourt, C.; Honess, P.; Perkin, A.; Pimley, E.; Pullen, S.; Svoboda, N. (2003). Species-Typical Patterns of Infant Contact, Sleeping Site Use and Social Cohesion among Nocturnal Primates in Africa. Folia Primatologica, 74 (5-6), 337–354.
- Charles-Dominique, P. (1977). Ecology and behaviour of nocturnal primates: prosimians of equatorial West Africa. Columbia University Press.
- Charles‐Dominique, P. (1977). Urine marking and territoriality in Galago alleni (Waterhouse, 1837—Lorisoidea, Primates)—a field study by radio‐telemetry. Zeitschrift für Tierpsychologie, 43(2), 113-138.
- Ambrose, L. (2003). Three acoustic forms of Allen’s galagos (Primates; Galagonidae) in the Central African region. Primates, 44(1), 25-39.
- Nash, L. T., Bearder, S. K., & Olson, T. R. (1989). Synopsis of Galago species characteristics. International Journal of Primatology, 10(1), 57-80.
- Hayssen, V. D., Van Tienhoven, A., & Van Tienhoven, A. (1993). Asdell’s patterns of mammalian reproduction: a compendium of species-specific data. Cornell University Press.
- Svensson, M. S., Morcatty, T. Q., Nijman, V., & Shepherd, C. R. (2021). Shedding Light on the Trade in Nocturnal Galagos. Primate Conservation, 35, 157-168.
Written by Divya Pawar, September 2022