The western lowland olingo is smaller than the northern olingo, but larger than the most montane member of the genus, the recently described olinguito ("little olingo").[2] While the Panamanian subspecies B. m. orinomus is about the same size as the eastern lowland olingo, the subspecies from west of the Andes, B. m. medius is smaller.[2] The pelage is slightly lighter than that of the eastern species.[2]
It has a head-body length of 31 to 41 centimetres (12 to 16 in), with a tail length of 35 to 52 centimetres (14 to 20 in).[2] It weighs .9 to 1.2 kilograms (2.0 to 2.6 lb).[2]
There are two subspecies of the western lowland olingo: the nominateB. m. medius (Colombia and Ecuador) and B. m. orinomus (Panama and possibly Colombia).[2] The closest relative of the western lowland olingo is the other lowland olingo species, B. alleni, found east of the Andes, from which it diverged about 1.3 million years ago.[2]
