If you are ever told that you should be over something that happened in your distant past, you now have the perfect recovery. Sumatran rhinoceroses suffered a population slump nearly a thousand years ago, and it’s a significant part of the reason that the species is endangered now. To put it differently, take all the time you want.
There are just 200 Sumatran rhinoceroses (Dicerorhinus sumatrensis) left from the wild, making them among the most endangered mammals on the planet. It’s easy to assume their problems, as with so many other species, are humankind’s fault, and that is certainly partly correct. However, new research in Current Biology suggests the Sumatran rhino’s resilience against the harm we’re doing to their own ecosystem was greatly reduced by events at the middle Pleistocene.
Dr Herman Mays of Marshall University, West Virginia, sequenced the genome of a man Sumatran rhino called Ipuh, who died in Cincinnati Zoo four years back. “Our genome sequence data demonstrated the Pleistocene was a roller-coaster ride for Sumatran rhinoceros populations,” Mays said in a statement.
Around 900,000 years back, very low sea levels meant many Indonesian islands were joined into the Malay Peninsula in a place known as Sundaland. Numerous species flooded south of Asia, displacing locals that were unready for its contest.
Relatives of those now-extinct wooly rhino were among those arriving species, attaining a public summit of over 50,000 since they spread across the available selection. Fluctuating sea amounts fragmented habitat like roads or farms do now, leaving isolated pockets with too few members to keep genetic diversity. By 9,000 years back, there were likely just 700 Sumatran rhinos surviving.
“Their population bottomed out and never showed signs of recovery,” Mays said. No doubt that the presence of people in this age wasn’t helpful to the rhinos, but they managed to maintain a toehold of survival until the current combination of poaching and forest destruction, which appears likely to extinguish the diminished species, at least outside zoos.
Mays described this history utilizing a combo of what we understand about sea levels over the last couple of million years and genetic data utilizing a pariwise sequential Markovian coalescent (PSMC), which quotes the breeding population of a species over time based on a single individual’s genome. PSMC identifies periods when population numbers were low, decreasing the genetic diversity within a population so the genes from each parent have a recent common ancestor. However, Mays acknowledges from the paper it does a poor job of identifying recent changes in population numbers.
Even though the future of rhinos in the wild seems gloomy, Ipuh contributed to the species’ survival, with two sons and, so far, two toddlers.