Southern white rhinoceros

Physical features

• Rhinos are the second largest extant land mammal, smaller only than elephants. White rhinos are the largest species of rhino, although the greater one-horned rhino is similar in size.

• Both sexes are similar in length (12-15 feet) and shoulder height (5-6 feet), although males tend to be larger, heavier and may have shorter, thicker horns. Average weights are about 4,000 pounds (1,800 kg) for females and 5,100 pounds (2,300 kg) for males. Their heads alone can weigh 800-1,000 pounds.

• Their primary horns can be 37-79 inches (94-201 cm) in length.

• White rhinos are almost hairless, with hair only at the tip of the tail and fringes of the ears.

• Their feet feature three toes, the middle toe being the largest and supporting most of their weight.

• White rhinos are actually gray in color. It’s widely believed their name derives from the Afrikaans word wyd, meaning “wide mouth,” which may have translated to “white” over time.

Diet: Herbivore

• Wild – almost exclusively short grasses; During dry spells, they can go up to five days without drinking water.

• Zoo – Bermuda hay, fresh produce, alfalfa, herbivore chow, vitamin supplements

Reproduction

Breeding Behavior

• While both males and females reach sexual maturity around 4 or 5 years of age, they typically do not breed until they are older. Females may begin breeding around age 6 or 7. Males may not breed until they are 10 to 12 years old due to competition with older males. Both males and females typically breed into their teens and some into their late twenties.

• Mating may occur any time of year when a female is in estrous. However, peaks have been observed from October to December in South Africa and from February to June in East Africa.

• Estrus cycles are typically 30-45 days but can be as long as 60-70 days. During each cycle, males express interest in females for 24-48 hours and females are receptive to breeding for only 12-18 hours.

• Interbirth intervals range from 24-48 months and average 30 months.

• In human care, artificial insemination (AI) is an option when natural breeding is not successful. The first successful AI in a rhinoceros was reported in 2007.

• The only form of contraception is managing populations to prevent breeding (i.e., separating males and females). Surgery or hormone suppression are only used in older individuals for clinical reasons.

Pregnancy & Birth

• Females experience a variety of physical and behavioral changes during pregnancy, such as udder growth and reduced tolerance toward herd mates. Toward the end of the pregnancy, females may experience a swollen outer genital and avoid or be aggressive toward the male.

• Gestation averages 16-17 months.

• At the onset of labor, the female may retreat to a quiet place, refuse to eat, urinate frequently, and generally appear uncomfortable.

• Labor typically lasts about 40 minutes but can last up to 3 hours. Parturition usually occurs in about 10-20 minutes. Births usually occur in the evening or overnight.

• The placenta is discharged right after the calf and is often ingested by the mother. This is common in the animal kingdom.

Calves

• Calves are born weighing 90-155 pounds (40-70 kg) and can gain up to 10 pounds per day for the first ten days.

• Calves commonly stand up within 15-30 minutes of birth, but it may take 1-2 hours.

• Nursing should begin within 1-2 hours of standing. Infants less than two months old may nurse hourly, while older calves nurse every 2-3 hours.

• Although weaning may begin as soon as one month after birth, calves may continue to nurse for up to two years. Male calves are typically weaned earlier than female calves.

• A calf stays with its mother until she gives birth to a new calf, typically after two to four years. When this occurs, the older calf may stay in the herd with their mother and her new calf, or they may find a new companion of similar age and the same sex.

Interpretive Information

• The closest extant relatives of rhinos are tapirs. Both animals are in the Order Perissodactyla, also known as odd-toed (or odd-hoofed) ungulates. Other Perissodactyls include horses, asses and zebras.

• White rhinos are the most social of the rhino species. They may gather in groups of up to a dozen individuals, usually subadults or females without calves. A group of rhinos is called a crash or a herd.

• Due to limited overlap in the field of vision of each eye, rhinos have poor eyesight. They can discern moving objects more easily than stationary objects, which they can only see between 50-80 feet (15-25 meters) away.

• Rhinos rely heavily on their senses of smell and hearing. They can move their ears independently to determine the direction of a sound’s source.

• Males are more territorial than females. While male-female home ranges may overlap, ranges of adult males typically do not. Territorial borders are marked with urine. Water holes are often located at the boundaries of several territories, like pie slices. While males aggressively defend their territory from other males, they are generally non-aggressive toward females. Dominant males may attempt to prevent females in estrous from leaving their territory.

• Southern white rhinos are one of two subspecies of white rhino. The northern white rhino is critically endangered with only two individuals known to exist. The last male northern white rhino died in March 2018. As of January 2020, two female northern white rhinos live at the Ol Pejeta Conservancy in Kenya.

• The San Diego Zoo Institute for Conservation Research is working with southern white rhinos as a model for developing advanced reproductive technologies to establish a sustainable population of northern white rhinos using banked genetic materials (embryos, sperm, cell cultures, etc.) in their Frozen Zoo® collection.

Updated March 2020