The Calabar angwantibo is nocturnal and arboreal. The Calabar angwantibo weighs between 266 and 465 grams. Unlike the Calabar angwantibo, the golden angwantibo has no nictitating membrane. It shares the genus "Arctocebus" with the golden angwantibo ("Arctocebus aureus"). The golden angwantibo ("Arctocebus aureus") is a strepsirrhine primate of the family Lorisidae. Stephen Maturin acquires a Calabar angwantibo on his travels and becomes 'absurdly attached' to it. The Calabar angwantibo is the only primate to have a functioning nictitating membrane (third eyelid). The Calabar angwantibo lives in the rain forests of west Africa, particularly in tree-fall zones. If the attacker persists, the angwantibo will bite it and not let go. During the day the angwantibo sleeps under dense foliage, hanging from a branch.