Rusa unicolor (Kerr, 1792), or sambar, is the largest Oriental deer. Seven subspecies occur in varied habitats and elevations from India and Sri Lanka throughout southeastern Asia. Body mass and antler length decrease from west to east. R. unicolor is considered ancestral relative to the form of its male-only antlers and social behavior. Populations are vulnerable because of overexploitation for subsistence and markets in meat and antlers. R. unicolor was elevated by the International Union for Conservation of Nature and Natural Resources from no status in 2006 to “Vulnerable” in 2008 because of >50% decline in many populations over the past 3 generations. It is well represented in zoos and private collections and is introduced in Australia, New Zealand, South Africa, and the United States.