The Brown Greater Galago (Otolemur crassicaudatus), also known as the large-eared greater galago or thick-tailed galago, is a nocturnal primate, the largest in the family of galagos. As opposed to smaller galago species it would climb, walk or run rather than leap. Two subspecies of Otolemur crassicaudatus are recognised:

• O. c. crassicaudatus

• O. c. kirkii

The IUCN considers the silvery greater galago as a third subspecies, O. c. monteiri. Other sources treat it as a separate species, though with "misgivings". The IUCN Red List assesses all three forms individually as Least Concern.

This species is common in Southern and East Africa. The largest populations are found in Angola, Tanzania, southern Kenya and the coast of Somalia. The brown greater galago lives in tropical and subtropical forest, preferring riverine and coastal forest, but it can also be found in the woodland savannah. The subspecies display different ranges: O. c. crassidautus is only found in the KwaZulu-Natal region. O. c. kirkii is found from Massangena north to Vila Coutinho, Mozambique and Malawi.

The brown greater galago is a nocturnal, arboreal animal. During the day, it rests 5 to 12 meters above the ground in a dense tangle of creepers or in the hollow of a tree, rarely on an exposed branch. Female galagos will make nests, leafy platforms with foliage above to shelter their young. An individual galago may have several sleeping sites throughout its home range. At night, it emerges to forage for food. It moves quadrupedally through the trees or bush. This species is capable of short jumps from tree to tree when necessary. Its diet consists of fruit (like berries, figs), seeds, acacia gum, flowers, insects, slugs, and even reptiles, small birds and mammals. An individual galago on average spends 50% of its time each night traveling and only about 20% of its time foraging. It will often follow the same patrol pathway every night. Galago lifespan in captivity is 18 years or more. It is likely that life expectancy in the wild is lower.

This species is solitary, living in a home range of a few hectares; however, there is some overlap with other individuals. Males have territories that overlap with a few females and females may have home ranges that overlap, but male territories generally do not overlap. Males tend to have a larger territory than females. The territory is marked by urine and a scent produced in a gland in the chest. Social interaction generally occurs at sites of range overlap, sites of large gum resources or prime sleeping trees. Social play is also exhibited by juveniles, sub adults and adult females with juveniles. Social grooming is absent in the greater galagos compared to other primate species. It is instead filled with a behavior known as reciprocal licking to clean each other's fur.

Vocal communication is very important in galago species with significant research systematically identifying types of calls including: raucous cry call, alarm call, contact rejection calls, distress call, infant call, mother call, advertising call.

Kirk’s Large-eared Galago (Bushbaby) (Otolemur crassicaudatus kirkii) - needs confirmation for subspecies