An international team of scientists has produced the first whole-genome sequence for the endangered Sumatran rhinoceros (Dicerorhinus sumatrensis), the smallest of the five living rhino species and is one of the three species native to Asia.
This is a photograph of Ipuh, the Sumatran rhinoceros (Dicerorhinus sumatrensis) at the Cincinnati Zoo. Image credit: Tom Uhlman.
The Sumatran rhinoceros is a plant-eating browser that belongs to the order Perissodactyla.
The animal can reach a shoulder height of 3.67 – 4.76 feet (1.12 – 1.45 m). It has a body length of 7.7 – 10.4 feet (2.36 – 3.18 m) and a tail length of 14 – 28 inches (35–70 cm). The weight is reported to range from 500 to 1,000 kg.
The species can be easily recognized by the two deep skin folds encircling the body between the legs and the trunk, and its thick pelage of short stiff hairs. Two horns decorate the snout, although the frontal horn is much more conspicuous than the nasal horn.
The Sumatran rhino has relatively poor eyesight, relying more on hearing and smell to detect what is going on around them. The ears of the animal possess a relatively wide rotational range to detect sounds and an excellent sense of smell to readily alert them to the presence of predators.
The animal once occurred from the foothills of the Himalayas in Bhutan and north-eastern India, through southern China, Myanmar, Thailand, Cambodia, Lao PDR, Viet Nam and the Malay Peninsula, and onto the islands of Sumatra and Borneo in Indonesia.
Hunting and habitat loss have made it one of the rarest large mammals and the species faces extinction despite decades of conservation efforts. By 2011, only about 200 of the Sumatran rhinos were thought to remain living in the wild.
“This species has been well on its way to extinction for a very long time,” said co-author Terri Roth, from the Center for Conservation and Research of Endangered Wildlife at the Cincinnati Zoo and Botanical Garden.
According to the team, the Sumatran rhinoceros population peaked at a time when fossil evidence shows an invasion of continental mammals into Sundaland, around 900,000 years ago.
“By about 12,000 years ago — the end of Pleistocene — many large mammals had suffered, and Sumatran rhinos were no exception,” the researchers said.
“Rising sea levels submerged the Sundaland corridor, and land bridges connecting the islands of Borneo, Java, and Sumatra to the Malay Peninsula and mainland Asia disappeared into the ocean.”
“Most likely as a result, the population of rhinos shrunk as suitable habitat became increasingly fragmented. Since that time, Sumatran rhinoceros populations have only dwindled further due to increasing pressures related to habitat loss and hunting.”
“Their population bottomed out and never showed signs of recovery,” said lead author Dr. Herman Mays, Jr., of Marshall University.
The scientists came to these conclusions by using an approach called pairwise sequential Markovian coalescent.
“We estimate that the Sumatran rhinoceros population peaked at an estimated effective population size of approximately 57,800 individuals about 950,000 years ago,” they said.
“By 9,000 years ago, the genome evidence suggests, the effective population size was reduced to only about 700 Sumatran rhinos.”
The findings suggest that climate change in the distant past reduced the genetic diversity of Sumatran rhinos, leaving them even more vulnerable to later pressures from human activity.
“The DNA sample that we sequenced belonged to a rhino named Ipuh, after the locality on the island of Sumatra where he was originally collected,” the authors said.
“Ipuh lived at the Cincinnati Zoo for 22 years until his death in 2013, and his remains are still on display at the Cincinnati Museum Center. Two of Ipuh’s sons continue to live at the Sumatran Rhino Sanctuary in Sumatra. One of them has already sired two calves.”
“The Sumatran rhinoceros species is hanging on by a thread. We need to do more to save it,” Roth said.
The research is published in the journal Current Biology.
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Herman L. Mays Jr. et al. Genomic Analysis of Demographic History and Ecological Niche Modeling in the Endangered Sumatran Rhinoceros Dicerorhinus sumatrensis. Current Biology, published online December 14, 2017; doi: 10.1016/j.cub.2017.11.021
