The white rhino is considered the most sociable of rhino species (11). Females can usually be seen with their most recent offspring, which they stay with until the next calf is born (12). Larger, temporary associations of 14 or more individuals can also occasionally be observed (5), with immature individuals typically grouping together, as do mothers without calves (12). Dominant males, however, are usually solitary and occupy smaller home ranges than females (5), marking their boundary by spreading dung, defecating on well-used dung-piles known as 'middens', spraying urine, dragging their feet and damaging plants with their horns (4). While the dominant male will tolerate females and sub-adult males within their territory, and will attempt to keep receptive females from leaving, any invading bull will quickly be confronted (5). However, fights are rare and confrontations usually consist only of slight horn butting, false charges, and other displays (4). Breeding occurs throughout the year. After the courtship and mating period, which lasts from one to three weeks, the female may leave the bull's territory. Gestation lasts around 16 months and the single calf is very active soon after birth (4). If threatened, the mother will stand guard over her young, but otherwise the infant usually runs ahead of its mother (12). Calves are weaned anywhere from one to two years after birth. The normal interval between calves is two to three years (13). Sexual maturity is reached around six years in females and 10 to 12 years in males (4). White rhinos are grazers, feeding on large quantities of grasses that they crop with their wide, square front lip (4) (5). Individuals also drink water from watering holes almost daily; although they can survive for four or five days without water when conditions are dry (12). All rhinoceroses have poor eyesight, but good hearing and a very good sense of smell, on which they depend (5) (12).