Offspring for Sumatran rhinos

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.