Offspring for Sumatran rhinos (Dicerorhinus sumatrensis): Critically Endangered (IUCN) with only 100 individuals

A new study examines the decline of the Sumatran rhino in Borneo. It concludes that the remnant populations of Sumatran rhinos can only be rescued by combining efforts of total protection with stimulation of breeding activity. The researchers suggest to resettle small isolated populations and to undertake measures to improve fertility. The case of the recently captured female rhino in Kalimantan, Borneo shows the importance of immediate action. Forschungsverbund Berlin e.V. (FVB)

The Sumatran rhinoceros, also known as hairy rhinoceros or Asian two-horned rhinoceros (Dicerorhinus sumatrensis), is a rare member of the family Rhinocerotidae and one of five extant rhinoceroses. It is the only extant species of the genus Dicerorhinus. It is the smallest rhinoceros, although it is still a large mammal. This rhino stands 112–145 cm high at the shoulder, with a head-and-body length of 2.36–3.18 m  and a tail of 35–70 cm. The weight is reported to range from 500 to 1,000 kg , averaging 700–800 kg, although there is a single record of a 2,000 kg specimen. Like both African species, it has two horns; the larger is the nasal horn, typically 15–25 cm, while the other horn is typically a stub. A coat of reddish-brown hair covers most of the Sumatran rhino's body.

Members of the species once inhabited rainforests, swamps, and cloud forests in India, Bhutan, Bangladesh, Myanmar, Laos, Thailand, Malaysia, Indonesia, and China. In historical times, they lived in southwest China, particularly in Sichuan. They are now critically endangered, with only six substantial populations in the wild: four on Sumatra, one on Borneo, and one in the Malay Peninsula. Their numbers are difficult to determine because they are solitary animals that are widely scattered across their range, but they are estimated to number fewer than 100. Survival of the Peninsular Malaysia population is in doubt, and one of the Sumatran populations may already be extinct. Total numbers today may be as low as 80. In 2015, researchers announced that the Eastern Sumatran rhinoceros is extinct from north part of Borneo (Sabah, Malaysia).

A new study examines the decline of the Sumatran rhino in Borneo. It concludes that the remnant populations of Sumatran rhinos can only be rescued by combining efforts of total protection with stimulation of breeding activity. The researchers suggest to resettle small isolated populations and to undertake measures to improve fertility. The case of the recently captured female rhino in Kalimantan, Borneo shows the importance of immediate action. The article has been published in the scientific journal Global Ecology and Conservation.

A consortium of international scientists examined the historical development of the Sumatran rhinos in Borneo. Their study identified the low reproduction of females in combination with hunting as the main cause for the current decline of rhinos. "Females do not find a mating partner within the small isolated populations any more," explains Petra Kretzschmar, scientist at the Leibniz Institute for Zoo and Wildlife Research (IZW), "the long non-reproductive periods lead to the development of reproductive tract tumours." Only a combination of intensive protection with improvements of the reproductive performance can save the species from extiction. The researchers recommend resettling populations of less than 15 individuals to highly protected areas. Here, reproductive health should be monitored on a regular basis and individual female fertility (conception) should be optimised by using assisted reproduction techniques.

For their study, the scientists compared historical data with recent developments about the Borneo rhino (Dicerorhinus sumatrensis harrissoni), one of two extant subspecies of the Sumatran rhino. The researchers used mathematical models to reconstruct the decline of the rhino population in the Tabin Wildlife Reserve (TWR) in the Malayan state Sabah of Borneo. A study on habitat use completed the picture. Here, the scientists analysed data collected over a span of 13 years and identified the characteristics describing the preferred habitat of the rhinos.

Today, only two subspecies of the Sumatran rhino exist, D. s. sumatrensis in Sumatra, Indonesia, and D. s. harrissoni, in Borneo in the states of Sabah, Malaysia, and Kalimantan, Indonesia. 

Currently, there are still around 100 individuals in Sumatra but the Sumatran rhino on Borneo is nearly extinct. 

The decline of the rhino population in Sabah has been documented in detail for the first time in this new study. Many animals were still spotted in 2000. By 2013, the scientists did not register a single rhino individual left. One of the last Borneo rhinos has been recently captured in the state of Kalimantan, the southern part of Borneo belonging to Indonesia. "The captured animal was one of the last females of its species" says Kretzschmar of the IZW, "it died right after capture due to an infection of a snare wound."

The reasons for the catastrophic decline of the Sumatran rhinos have not been previously clear. Data necessary to improve decisions for conservation management of the rhinos was missing or fragmentary. The new study closes this gap. It demonstrates that a combination of techniques can do much to illuminate causes of population declines, improve decision making for conservation management and possibly prevent similar developments in populations of other species of similar ecological standing.

The catastrophic decline ofmore species of the big area of South East Asia are in the deforestation, palm oil plantations and poachers.