White Rhinoceros

One of the largest mammals lumbering on land, the White Rhinoceros, or square-lipped rhinoceros, is second only to the mighty African elephant in size. Despite its name, it is not actually white, and thus, it is believed that the word ‘white’ could have stemmed from a mistranslation of the Dutch word ‘wijd,’ which means ‘wide,’ referring to their broad, square-shaped mouth. Interestingly, their mouth is way broader, and their head bigger than those of their African neighbors, the Black rhinos. 

The white rhinos are considered a ‘keystone species’ as they help increase the biodiversity of grasses and are also believed to play an important role in preventing forest fires.

Subspecies

There are two subspecies of white rhinoceros.

• Southern white rhinos (Ceratotherium simum simum)
• Northern white rhinos (Ceratotherium simum cottoni)

Description

Size:

Length: Head-Body – 11.0 to 13.7 ft (132 to 164.4 inches); Tail – 0.7 m (2.3 ft); Front horn – 0.94 to 2.01 m (37 to 79 inches); Rear horn – 0.55 m (22 inches)

Height: Shoulder – 1.5 to 1.8 m (4.9 to 5.9 ft)

Weight: 1000 to 3800 kg (1.0 to 4.1 tons)

Body and Coloration:

White rhinos have a giant body and a broad chest, along with a noticeable hump on the back of their neck, making them the largest of the five living rhinoceros species. The skin is tough and gray with plate-like epidermal folds, and they have no hair on their body except for ear fringes, eyelashes, and tails.

These rhinos have two highly keratinized horns on their snout, long and flexible ears, and a wide, square-shaped mouth adapted for grazing. Although large in build, they have relatively small eyes with poor vision and thus rely on auditory and olfactory cues to sense their environment. Of all terrestrial animals, their nostrils are the widest, and their olfactory passages are larger than their brains, enabling them to pay attention to movements around them. 

The Southern white rhinos are relatively larger and less hairy than the Northern ones, whereas, in both subspecies, the males are larger than the females.

Distribution

The Southern white rhinos were initially native to South Africa, while the Northern subspecies were spread in northwestern Uganda, southern Chad, southwestern Sudan, the eastern part of Central African Republic, and northeastern Democratic Republic of the Congo (DRC). Currently, the latter is restricted to the DRC, with only two extant females, while most of the southern subspecies are spread across Namibia, Zimbabwe, South Africa, and Kenya. A few southern white rhinos are also found in Botswana, Ivory Coast, and Zambia.

Habitat

These animals live in open habitats like long and short grass savannas, woodlands, and dense forests adjacent to water bodies. In the mornings, they frequent the banks, moving to more shady areas as the temperature rises.

Diet

These rhinos are exclusive herbivores, feeding on grass varieties like signal grass, finger grass, and panic grass found in shaded areas of their foraging range. They also consume other plant parts like flowers, fruits, seeds, stems, and nuts.

Behavior

• During winters, they are diurnal, foraging during the day when temperatures are high. But in summer, they are crepuscular, active around dawn and dusk to avoid the scorching heat.
• These rhinos eat for about half of the day, rest for one-third, and spend the rest doing other activities. They must drink water every 2 to 4 days but can even live up to 5 days without it.
• Most adult bulls live solitary lives, while only the females live in herds with their calves and the sub-adults.
• For territorial marking, dominant bulls brush their horns and scrape the ground with their feet, spraying urine on the brush. These bulls may also lay about 20 to 30 dung piles on the ground to declare autonomy over their territory.
• They communicate using a wide variety of vocalizations. When confronted by a conspecific, the males rumble and snort fiercely, while the females bellow and growl. Despite sounding similar, these calls differ in frequencies, allowing white rhinos to communicate from distant locations and identify each other.
• While white rhinos are not naturally aggressive, they have a distinctive attack pattern against their predators. They rush towards the aggressor at speeds as high as 50 km/h and repeatedly strike the ground with their hind feet during the run. The females are generally more protective towards their calves and thus attack the enemies more ferociously than the males.
• The home ranges of male white rhinos are usually between 0.75 to 13.80 square kilometers, whereas females have relatively smaller ones, ranging between 0.5 to 2.3 square kilometers. These rhinos also tend to have greater home ranges in dry seasons when they forage more extensive areas than in wet seasons, during which they explore less.

Lifespan

White rhinos have an average lifespan of about 50 years in the wild. In captivity, the highest recorded lifespan of northern and southern white rhinos is 30 years.

Reproduction and Life Cycle

The mating system in white rhinos is polygynandrous, with both males and females mating with multiple partners. Females attain sexual maturity at around 5 to 7 years, while males mature between 10 and 12. They generally breed throughout the year, peaking between October and December in South African subpopulations and February to June in East African subpopulations.

During the breeding season, a female enters a male’s territory, and the latter thoroughly investigates her to ensure she is sexually receptive. A female in estrus is recognized by the smell of urine and dung and the frequency of urination. If the male feels she is ready to mate, he follows her for 3 to 5 days, during which the female reciprocates vocally. This pair bond could last up to 20 days before mating, with the male putting religious efforts into preventing his partner from entering another male’s territory.

While copulating, the female curls her tail and stiffens her body and the male mounts her from behind. This copulatory phase lasts for about 30 minutes, with the male ejaculating in intervals of about 5 minutes. The testosterone levels in the male remain high over the next 2 to 5 days; hence, mating continues till the hormone levels drop.

The gestation period of 16 months is followed by the birth of a single offspring weighing between 40 and 65 kg (88 and 143 lbs). The calves start suckling within a few hours after birth and may continue over the next 12 months. While they begin grazing around two months of age, they depend entirely on their mothers until six months for nutrition. The mothers protect their calves from imminent predators and other environmental threats till about two or three years, after which they are independent enough to venture into the world alone.

Predators

Their most dangerous predator is humans, who illegally poach them for their horns and hide. Though these rhinos have very few natural predators, they are sometimes injured and killed by lions and spotted hyenas.

Adaptations

• They have broad, square-shaped mouths with wide, prehensile lips that help them graze large quantities of grass at once.
• Their front and back feet have three toes each, covered by a soft, elastic sole to balance the weight of their bulky body.
• Like all rhinos, they wallow in mud holes during summers and on the sand during winters to regulate their body temperatures. Besides acting as a sunblock and a parasite-repellent, the mud on the rhino’s body matches the color of the soil, helping it camouflage against the background.

Conservation Status

According to the IUCN Red Data List, the white rhinos are considered ‘Near Threatened (NT).’ However, each subspecies has been provided a separate status based on their current population size. 

The Southern White Rhinos are also listed as NT in the IUCN Red Data List and in Appendix II of CITES. They were once considered extinct in the wild, but the discovery of four individuals in Zululand (now South Africa) in 1883 gave a ray of hope. To conserve and expand the existing population, strict laws were implemented as early as the 1950s, but their numbers declined drastically between the 1970s and 1980s due to extreme social turmoil and a series of civil wars in some African countries. To improve the situation, CITES banned the international trade of these rhinos, and most individuals were shifted to protected areas like national parks, increasing their numbers from 337 to 1,876 in the next twenty years. In 1994, the United States further threatened to suspend trade relations with nations that did not abide by the legal bans on the poaching of white rhinos, forcing African countries to consider the conservation of their white rhino populations seriously. Due to religious conservation efforts by these nations, about 16,000 Southern white rhinos are found worldwide today.

In contrast, the Northern white rhinos were once restricted to the relatively underdeveloped countries of Africa, where they continued to get poached for commercial purposes because of poor legal regulations and weak centralized governance. Their numbers plummeted from around 500 in the 1960s to only four individuals in 2015, which were then released into Ol Pejeta Conservancy in Kenya. Only two female rhinos are currently left, which has caused the subspecies to be classified as Critically Endangered (CR).