The mating system in white rhinoceroses is polygynandrous, meaning both males and females have multiple sexual partners. Male white rhinoceroses are vigilant for females who enter into their territory. Once the female enters the territory, the male remains with the female for a day to investigate whether the female is ready to mate. If the female is ready, then the male usually follows her for 3 to 5 more days, during which time the females responds with snorts and roars. Before mating, pair bonds last for 5 to 20 days; in this period if females attempt to enter another male’s territory, males block the way, and sometimes confrontation occurs between males and females. However, if females successfully enter into another male’s territory, then the previous male will discontinue his effort to follow the female.
Males detect whether females are ready to mate by the smell of urine; urine includes chemicals that signals females in estrus. Females usually experience their first estrus at the age of three and half years, but they don’t breed until age 5. Almost all females breed after 5 years of age. Some of the signs of mating behaviors sent by female rhinoceroses are frequent urination and whistling sounds.
Among males of the same population, fecal testosterone levels in territorial males are higher than the non-territorial males. Furthermore, territorial males usually spend more time with females and generally have more mating partners than non-territorial males. Thus, territorial males have higher reproductive success than non-territorial males.
While mating, male white rhinoceroses place both of their feet on the back of the female. Copulation lasts for 15 to 30 minutes on average, with ejaculations every 4 to 5 minutes. Mating behavior continues for 2 to 5 days as testosterone levels of male are high for 2 to 5 days. After that, the female leaves the male’s territory.
White rhinoceroses breed throughout the year, but breeding usually peaks between October to December in southern African populations and February to June in eastern African populations.
White rhinoceroses give birth to one offspring at a time, which weighs, on average, 48.5 kilograms at birth, and doubles its size by 6 months. Females reach sexual maturity at the age of 3 to 5 years, whereas males reach sexual maturity at the age of 5 to 7 years. Female white rhinoceroses can reproduce from age 5 up to the age of 46 years. The breeding interval in white rhinoceroses is long, 2.5 to 3 years. This long breeding interval is tied to a long gestational period of 530 to 550 days. Calves usually start weaning at one year, and leave their mothers once they reach 2 to 2.5 years of age.
White rhinoceros calves start suckling mother’s milk only hours after birth, and they usually suckle for 2 to 3 minutes at a time. Mothers are the sole caregivers of the young and males have no parental investment on calves beyond the mating process. White rhinoceroses start grazing at 2 months, but they are dependent on their mothers for nutrition until 6 months after birth. Beyond age 6 months, mother still nurse the child and protect them from predators and external threats, such as wildfire.
Furthermore, calves usually move in front of their mother in the early stage of their life, and they respond immediately when their mothers change direction. Calves usually follow their mothers continuously for 2 months. White rhinoceros stay with their mother for 2.5 to 3 years. At that time, the mothers drive their calves out of their territories and become sexually receptive again.