Which zoos in the Usa have okapi in mixed exhibits, and which what species, I guess, mostly duikers ? I know, the Us-zoo change their combinations from time, so I think, San Diego WAP does still have them with yellow-backed duikers, so most okapi holders do,I belive ? I'm not sure about L.A and San Diego Zoo if both keep them together with Black Duikers ? Any other duikers, small antelopes or other species kept together with Okapi ? In europe,most common combo is Okapi/red Duiker ( of course not many duiker species have left)and I think, now with some birds at Rotterdam and Doue La Fontaine.
Columbus Zoo has exhibited okapi with three species of duiker - yellow-backed, red-flanked, and black. At one point, the exhibit may have included okapi, duiker, and yellow-backed duiker. (I believe the signs included all three species, but the bongos in Columbus's collection were not around for long, and I'm not sure that I ever saw all three species together in the same exhibit.) The most impressive mix of animals in exhibit containing okapis is one of the "savannas" at Disney's Animal Kingdom Lodge. As of two weeks ago, okapis are kept with blue crane, waterbuck, nyala, impala, red river hog, northern ground hornbill, and ruppell's griffon vulture. (Thanks to geomorph for the list)
Doue La Fontaine also includes Hamlyn's monkeys in the same exhibit, it looks mighty impressive! Can't think of many okapi enclosures that feature monkeys though.
San Diego Zoo's Safari Park did not have any duikers exhibited with the okapis when I visited in June; San Diego Zoo did have black duikers exhibited with okapis when I visited there in September 2014.