It is not unusual for livestock to disappear from pastures and herds and there are numerous possible causes. Young or small animals such as pigs, calves, lambs and kid goats frequently disappear. However, when no trace of the animals can be found, particularly when they have been well tended and confined to pasture, predation or theft may be the cause.
Livestock and their young normally remain close enough that young animals can nurse several times daily, particularly for the first few weeks after birth. Therefore, a lactating female with engorged udder, searching for her young for prolonged periods may be evidence that the young is missing or dead. This type of maternal behavior is less likely to occur where females have one remaining of two or more offspring. Because they behave differently and have large litters, hogs are less likely to respond in this fashion if several young remain.
Domestic animals are much less wary and nervous than wild species, particularly when they are herded or otherwise handled regularly. Their customary behavior is modified by weather, temperature, availability of feed and other factors. However, the behavior pattern is characteristic for each individual herd under a specific type of management.
Other livestock behavior is useful as indirect evidence of predation. The presence of carnivores which appear to exhibit a threat usually will cause most cows to bawl and attempt to locate their young. Their behavior will be alert, much exaggerated from normal and will include urgent calling, running to find their calves and attempts to chase the carnivores. Sheep and goats respond in a similar manner when alerted but they are much less aggressive than cattle. They do call urgently and attempt to find their young, but some may abandon their search and try to escape to protect themselves.
Almost without exception, the behavior of livestock in herds which are raided repeatedly by predators becomes more alert and defensive. They appear frightened even by common management practices that do not normally disturb them, especially when carnivore hunting behavior involves chasing the herd while making a kill rather than by stalking individual animals. Once established by repeated depredation, this response continues and will recur for days or weeks. With normal management, this unusual behavior will gradually disappear if predation stops. To the person versed in livestock production and familiar with the individual herd, abnormal behavior is readily apparent and indicates a reaction to an unusual disturbance.