a meal. Duiker as prey Hunting by walking was successful for duiker, steenbok and even kudu; during the hot dry season, in the central Kalahari. Fresh duiker hoof tracks were followed at a steady walk for 3 hours. Even when the animal was seen, rather than make any effort to keep it in sight, the hunter continued along the hoof tracks. The duiker was caught standing head lowered and tongue hanging out. The hunter walked up to it and clubbed it with a digging stick. Kudu as prey Several kudu hunts were performed, in the central Kalahari, for the documentary television program The Life of Mammals. The hunters prepared by drinking as much water as they could. The hunters searched for fresh tracks using a four-wheel-drive vehicle until they saw kudu and then hunted on foot; sometimes walking, sometimes running. The objective was to illustrate how they would perform persistence hunting, not to demonstrate that they could — so the hunters refilled their water bottles from the vehicle during the hunt. The hunters averaged for 4 to 5 hours, in temperatures of to . Persistence hunting is chosen when conditions are right: when there are prey animals already weakened by illness or injury or hunger or thirst; when tracking will be easier. Weaker kudu usually break away from the herd to hide. Predators may follow the stronger scent of the herd, giving the hidden animal a chance to escape. With that knowledge hunters look for tracks away from the herd and follow the weaker animal. Pronghorn as prey Modern examples: The pronghorn run very quickly for a quarter mile, sometimes a half mile, stop and stare until the runners catch up, and then take off again. The animals run in a broad clockwise arc, so the runners can take a shortcut straight across the arc and get within 50 yards. But the herd splits and merges until they can't tell whether they're chasing animals that have run for two minutes or 20 minutes or two hours. They chase on and off for two days without success. The fastest runner has a 2:10 marathon and the slowest a 2:45. They have come together to chase pronghorn across the New Mexico short-grass prairie on a day. After trailing a pronghorn buck for two hours they abruptly come across the animal 50 feet away, with a group of does. They close to 25