Rhinoceros – One-horned rhinoceroses

The genus of unicorn rhinos from Asia, swinging on the edge of existence

Two extant and endangered species of this genus, Rhinoceros sondaicus (the Javan rhinoceros) and Rhinoceros unicornis (the Indian rhinoceros), represent some of the most emblematic yet critically threatened wildlife in Southeast Asia. These majestic creatures are distinguished by a singular nasal horn, a feature more commonly developed in males, with females rarely sporting this characteristic. This horn, slightly curved backward, is not just a hallmark of their identity but also a central figure in the challenges they face, being highly sought after for illegal wildlife trade.

The one-horned rhinoceros possesses unique dental features, including incisors and lateral tusk-like incisors, adapted for its specific dietary needs. Its prehensile upper lip is another distinctive trait, allowing it to grasp and pull foliage expertly during feeding. This adaptation underscores its primarily browsing lifestyle, contrasting with some of its African relatives, who are more inclined towards grazing.

Their habitats are as diverse as Southeast Asian ecosystems, ranging from plain alluvial grasslands to swamps and dense tropical rainforests. This variability in habitat preference demonstrates their adaptability but also highlights their sensitivity to human activity and presence, which has dramatically shaped their distribution and survival.

Scientific investigations into the evolutionary history of rhinoceroses have revealed fascinating insights. Molecular studies estimate that the divergence between the Asian and African rhinoceros lineages occurred approximately 26 million years ago (mya). Further phylogenetic analysis elucidates the genetic distances within the rhinoceros family, showing that the genus Rhinoceros, to which the one-horned rhinoceros belongs, is distantly related to the African genera Ceratotherium (white rhinoceros) and Diceros (black rhinoceros). Intriguingly, it shares a closer relationship with the Sumatran rhinoceros (genus Dicerorhinus), suggesting a complex evolutionary web that has woven the story of these ancient creatures.