In the jungles of Borneo, the male proboscis monkey's huge nose is a sign of strength and fitness, used to intimidate rivals that might challenge him for his harem. Meanwhile, in Africa, the warthog typically goes uncontested as the ugliest of the continent's mammals. The burrowing star-nosed mole could win the blue ribbon for ugliness. They are hardly the pin-ups of the animal world, but, from warthogs and vultures to tapeworms and bats, the ugliest of nature's designs can still be beautiful - even when they aren't pretty.

Sunday, 11/18/07 from 8-9 p.m. ET