Okavango: Africa's Last Eden Naturalist and photographer Frans Lanting will lecture on Okavango, an isolated area in Botswana (formerly Upper Volta) that is the subject of his latest book. Lanting, an award-winning National Geographic photographer and 1991 BBC Wildlife Photographer of the Year, has documented the exotic and endangered species of the region. He will share his experiences in Eden through a slide presentation. We recommend purchasing tickets in advance, since the combination of stunning photography and passionate speakers has made these little zoo talks so popular that they often sell out. Gate 5 will open at 6:30 p.m., and the lecture will begin at 7:30. Houston Zoological Gardens, 1513 Outer Belt Drive, 529-2632. $8, $6 members.