National Geographic : 1991 Jan
STARK WHITE SPECK of a sailboatheads toward a rippled swath of dunes shaped by the tide near Steep Point in Shark Bay (right). Beneath the chubby bulk of a dugong, patches of sea grass sprout from the floor of the bay (above), home to more than a dozen varieties of the floweringplant. The grass forms a fundamental link in a food chain that includes shrimp and some 30 varieties of edible fish, basis of an important fishing industry. These underwater meadows also provide forage for the dugong, distant cousin of the manatee. Although Aborigines may legally hunt them, the number of dugongs in Australian waters has been relatively stable, and Shark Bay's population of 10, 000 is among the world's largest. Elsewhere throughout their rangedugongs are under siege for their meat, fat, and tusks; the creaturesare easy prey for poachers equipped with power boats, nylon nets, and even dynamite. Compounding the threat is the dugong's slow reproductionrate. Females usually don't mate until after age nine and produce but one calf every three to five years. The dugong's skittishness presents monumentalproblems for research ers. Working with a NationalGeo graphic Society grant, biologist Paul K. Anderson of the University of Calgary recently discovered that males stake out barrenpieces of terri tory called leks. They vigorously defend their leks in hopes of attract ing females, which venture forth only to mate. The intrusionof a chal lenger can mean violent combat between males, behavior that contradictsthe popular image of these mammals as gentle giants.