Otolemur crassicaudatus
greater galago

Thick-tailed galagos, or bushbabies, are found in East Africa from southern Sudan to eastern South Africa and through southern Angola.

These animals are forest dwellers (Nowak, 1983).

Otolemur crassicaudatus, also known as the thick-tailed galago, is the largest galago species. Head and body length ranges from 297 to 373 mm, and tail length from 415 to 473 mm. Body size is sexually dimorphic, with males being significantly larger than females. The coloration of the fur is silvery brown to gray with the underside usually lighter in color. The fur is dense, woolly, quite long, wavy, and usually described as without luster.

The ears of O. crassicaudatus are large and can be moved independently of each other backwards and towards the base of the ear. These primates often furl and unfurl their ears, giving them a quizzical expression.

The eyes are forward pointing and large. As with most galago species, there are flat disks of thickened skin at the ends of the fingers and toes useful in grasping limbs. The fingers are long, and the toes are flattened with flattened nails. The dental formula is I 2/2, C 1/1, P 3/3, M 3/3. (Kappeler, 1991; Nowak and Paradiso, 1983)

In most types of galagos, mating can be either monogamous or polygynous. The deciding factor appears to be the population density. Males tend to maintain larger home ranges than do females. They mate with females whose ranges are encompassed by their own. (Nowak and Paradiso, 1983)

The birth season of thick-tailed galagos varies according to locality. For example, breeding is restricted to November in the Transvaal, but occurs in August and September in Zambia. Pregancies peak in August in Zanzibar and Pemba. Female estrous cycles last approximately 44 days. Gestation is 133 days.

Litter size is generally 2 young, but can be 3. Females reach sexual maturity at 2 years of age. Because male competitive behavior is usually related to size in galagos, it is likely that males reach reproductive age somewhat later than do females. (Nowak and Paradiso, 1983)

After birth, females leave their young in the tree while they leave to forage. They produce a rich, energy-dense milk, especially in comparison with anthropoid primates. This may be related to their lifestyle, as anthropoid primates carry their young during lactation and this galago does not (Tilden, 1997; Nowak, 1983). The role of the male in parental care has not been described, but through defense of his home range, he may unintentionally help to protect and defend the young within the territory.

Species in the genus Otolemur have been reported to live in excess of 18 years in captivity. It is likely that wild individuals have a lower life expectency. (Nowak and Paradiso, 1983; Nowak and Paradiso, 1983)

Thick-tailed galagos are nocturnal and arboreal. In ideal situations, their population densities can reach 72 to 125 individuals per square kilometer. They are alert and agile, making leaps of up to 2 meters. Locomotion in O. crassicaudatus is generally quadrepedal unless disturbed. They are active for an average of nine and a half hours a day during summer and twelve hours per day during the winter. They sleep in nests that are 5 to 12 meters off the ground. Adult O. crassicaudatus sleep together during the day, but split up at night to forage. They move up to 1 kilometer through the night.

Otolemur crassicaudatus lives in small groups of 2 to 6 individuals. The composition of groups varies. It could be an adult pair with young, two adult females with young, or one adult female with young. Adult males are territorial, and they seek home ranges that overlap several female home ranges.

This galago communicates using several vocalizations. The young make a soft clicking sound to their mother. Adults make a louder clicking noise to call to other adults. There are also loud cries, barks, and a high-pitched alarm call.

Thick-tailed galagos also communicate through olfactory signals. They urine mark and urine wash. Urine washing is a behavior that spreads the urine all over the hands and feet to leave the scent over the entire space through which the animal moves (Nowak and Paradiso, 1983).

In addition, all galagos are known to have visual communication (body postures and facial expressions) and tactile communication (primarily grooming). (Nowak and Paradiso, 1983)

Thick-tailed bushbabies are mostly gumivorous and frugivorous; they are known to eat insects as well. In a study in South Africa, approximately 62% of the diet was gums and saps, supplemented by fruits and insects. The diet of O.crassicaudatus varies with locality. In the Transvaal, South Africa, insects were estimated to comprise 5% of the diet, whereas in Kenya, insects may account for 50 to 70% of the diet. One insect species which may serve as a seasonal food supply is Macrotermes falcigar, also known as large termites. When these termites are in the alate (winged) form, thick-tailed bushbabies have been observed eating them off the ground without using their hands. (Happold and Happold, 1992; Nowak and Paradiso, 1983)

Accounts of predation on this species are lacking the literature covered here. However, as small, nocturnal mammals, it is likely that snakes, owls, and small carnivorous mammals may prey upon them.

These animals are clearly important in local food webs. They prey upon insects, controlling the growth of insect populations. In additon, as a prey species, O. crassicaudatus may have a positive impact on the populations of its predators.

These animals, like other galagos, may occasionally be hunted as food. However, for the most part, they have no economic importance to humans. (Nowak and Paradiso, 1983)

There are no significant adverse effects of O. crassicaudatus on humans.

Although this species is rated "Lower Risk" on the IUCN Redlist, it is losing habitat due to humans clearing the land for farming and grazing animals.

As with all primates, galagos are listed in in Appendix II of CITES, limiting international trade in the animals or their parts.