Northern Sumatran rhinoceros (SciiFii)

The Northern Sumatran rhinoceros (Dicerorhinus sumatrensis lasiotis), also known as Chittagong rhinoceros and the northern hairy rhinoceros, is a subspecies of Sumatran rhinoceros that is native to the tropical rainforests, swamps, cloud forests, jungles and grasslands of the mainland Southeast Asia and eastern India. It also inhabits hilly areas, near rivers, steep upper valleys and mountains. The subspecies was once extinct since the early 20th century, but has since been brought back from extinction by SciiFii and reintroduced back to the subspecies' former range. The Northern Sumatran rhinoceros is the largest subspecies of Sumatran rhinoceros, usually weighing about as much as 2,000 kg (4,410 lb) and having a body length of around 250 centimeters (8.2 feet). It has longer hair on the ears and longer horns. However, it may occasionally have less hair on the body than the Western Sumatran rhinoceros (Dicerorhinus sumatrensis sumatrensis). Northern Sumatran rhinoceroses are solitary creatures except for pairing before mating and during offspring rearing. Individuals have home ranges; bulls have territories as large as 50 km2 (19 sq mi), whereas females' ranges are 10–15 km2 (3.9–5.8 sq mi). The ranges of females appear to be spaced apart; males' ranges often overlap. No evidence indicates Northern Sumatran rhinos defend their territories through fighting. Marking their territories is done by scraping soil with their feet, bending saplings into distinctive patterns, and leaving excrement.

The Northern Sumatran rhino is usually most active when eating, at dawn, and just after dusk. During the day, they wallow in mud baths to cool down and rest. In the rainy season, they move to higher elevations; in the cooler months, they return to lower areas in their range. When mud holes are unavailable, the rhino will deepen puddles with its feet and horns. The wallowing behaviour helps the rhino maintain its body temperature and protect its skin from ectoparasites and other insects. One 20-month study of wallowing behavior found they will visit no more than three wallows at any given time. After two to 12 weeks using a particular wallow, the rhino will abandon it. Typically, the rhino will wallow around midday for two to three hours at a time before venturing out for food. Although in zoos the Northern Sumatran rhino has been observed wallowing less than 45 minutes a day, the study of wild animals found 80–300 minutes (an average of 166 minutes) per day spent in wallows.

The Northern Sumatran rhino maintains trails across its range. These trails fall into two types. Main trails will be used by generations of rhinos to travel between important areas in the rhino's range, such as between salt licks, or in corridors through inhospitable terrain that separates ranges. In feeding areas, the rhinos will make smaller trails, still covered by vegetation, to areas containing food the rhino eats. Northern Sumatran rhino trails have been found that cross rivers deeper than 1.5 meters (4.9 feet) and about 50 m (160 ft) across. The currents of these rivers are known to be strong, but the rhino is a strong swimmer. A relative absence of wallows near rivers in the range of the North Sumatran rhinoceros indicates they may occasionally bathe in rivers in lieu of wallowing.

Most feeding occurs just before nightfall and in the morning. The Northern Sumatran rhino is a folivore, with a diet of young saplings, leaves, twigs, and shoots. The rhinos usually consume up to 50 kg (110 lb) of food a day. Primarily by measuring dung samples, researchers have identified more than 100 food species consumed by the Northern Sumatran rhinoceros. The largest portion of the diet is tree saplings with a trunk diameter of 1–6 cm (0.5–2.5 in). The rhinoceros typically pushes these saplings over with its body, walking over the sapling without stepping on it, to eat the leaves. Many of the plant species the rhino consumes exist in only small portions, which indicates the rhino is frequently changing its diet and feeding in different locations. Among the most common plants the rhino eats are many species from the Euphorbiaceae, Rubiaceae, and Melastomataceae families. The most common species the rhino consumes is Eugenia.

The vegetal diet of the Northern Sumatran rhinoceros is high in fiber and only moderate in protein. Salt licks are very important to the nutrition of the rhino. These licks can be small hot springs, seepages of salty water, or mud-volcanoes. The salt licks also serve an important social purpose for the rhinos—males visit the licks to pick up the scent of females in oestrus. Some Northern Sumatran rhinos, however, live in areas where salt licks are not readily available, or the rhinos have not been observed using the licks. These rhinos may get their necessary mineral requirements by consuming plants rich in minerals.

The Northern Sumatran rhinoceros is the most vocal of the rhinoceros species. Observations of the species in zoos show the animal almost constantly vocalizing, and it is known to do so in the wild, as well. The rhino makes three distinct noises: eeps, whales, and whistle-blows. The eep, a short, one-second-long yelp, is the most common sound. The whale, named for its similarity to vocalizations of the humpback whale, is the most song-like vocalization and the second-most common. The whale varies in pitch and lasts from four to seven seconds. The whistle-blow is named because it consists of a two-second-long whistling noise and a burst of air in immediate succession. The whistle-blow is the loudest of the vocalizations, loud enough to make the iron bars in the zoo enclosure where the rhinos were studied vibrate. The purpose of the vocalizations is unknown, though they are theorized to convey danger, sexual readiness, and location, as do other ungulate vocalizations. The whistle-blow could be heard at a great distance, even in the dense brush in which the Northern Sumatran rhino lives. A vocalization of similar volume from elephants has been shown to carry 9.8 km (6.1 mi) and the whistle-blow may carry as far. The Northern Sumatran rhinoceros will sometimes twist the saplings they do not eat. This twisting behavior is believed to be used as a form of communication, frequently indicating a junction in a trail.

Females become sexually mature at the age of six to seven years, while males become sexually mature at about 10 years old. The gestation period is around 15–16 months. The calf, which typically weighs 40–60 kg (88–132 lb), is weaned after about 15 months and stays with its mother for the first two to three years of its life. In the wild, the birth interval for this species is between four to five years. The reproductive habits of the Northern Sumatran rhinoceros have been studied in captivity. Sexual relationships begin with a courtship period characterized by increased vocalization, tail raising, urination, and increased physical contact, with both male and female using their snouts to bump the other in the head and genitals. The pattern of courtship is most similar to that of the black rhinoceros. The period of oestrus itself, when the female is receptive to the male, lasts about 24 hours, and observations have placed its recurrence between 21 and 25 days.

The conservation status of the Northern Sumatran rhinoceros is Endangered due to some habitat loss and, historically, poaching, however, thanks to the conservationists, the Northern Sumatran rhinoceros is a protected species and is making a comeback, with the population trend of the subspecies increasing.