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 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 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.
Captive specimens, deprived of adequate wallowing, have quickly developed broken and inflamed skins, suppurations, eye problems, inflamed nails, and hair loss, and have eventually died.
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 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.

There has been little opportunity to study epidemiology in the Sumatran rhinoceros.
Ticks and gyrostigma were reported to cause deaths in captive animals in the 19th century.
The rhino is also known to be vulnerable to the blood disease surra, which can be spread by horse-flies carrying parasitic trypanosomes; in 2004, all five rhinos at the Sumatran Rhinoceros Conservation Center died over an 18-day period after becoming infected by the disease.
The Sumatran rhino has no known predators other than humans.
Tigers and wild dogs may be capable of killing a calf, but calves stay close to their mothers, and the frequency of such killings is unknown.
Although the rhino's range overlaps with elephants and tapirs, the species do not appear to compete for food or habitat.
Elephants (Elephas maximus) and Sumatran rhinos are even known to share trails, and many smaller species such as deer, boars, and wild dogs will use the trails the rhinos and elephants create.

The 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.
Sumatran rhino trails have been found that cross rivers deeper than 1.5 m (4.9 ft) 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 Sumatran rhinoceros indicates they may occasionally bathe in rivers in lieu of wallowing.
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 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 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. Captive specimens, deprived of adequate wallowing, have quickly developed broken and inflamed skins, suppurations, eye problems, inflamed nails, and hair loss, and have eventually died. 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 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.
There has been little opportunity to study epidemiology in the Sumatran rhinoceros. Ticks and gyrostigma were reported to cause deaths in captive animals in the 19th century. The rhino is also known to be vulnerable to the blood disease surra, which can be spread by horse-flies carrying parasitic trypanosomes; in 2004, all five rhinos at the Sumatran Rhinoceros Conservation Center died over an 18-day period after becoming infected by the disease. The Sumatran rhino has no known predators other than humans. Tigers and wild dogs may be capable of killing a calf, but calves stay close to their mothers, and the frequency of such killings is unknown. Although the rhino's range overlaps with elephants and tapirs, the species do not appear to compete for food or habitat. Elephants (Elephas maximus) and Sumatran rhinos are even known to share trails, and many smaller species such as deer, boars, and wild dogs will use the trails the rhinos and elephants create.
The 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. Sumatran rhino trails have been found that cross rivers deeper than 1.5 m (4.9 ft) 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 Sumatran rhinoceros indicates they may occasionally bathe in rivers in lieu of wallowing.
Sumatran rhinoceros