Archival DNA Supports a Recent Onset of Otter Hybridization in Singapore

The smooth-coated otter (Lutrogale perspicillata) and the Asian small-clawed otter (Aonyx cinereus) are two otter species found throughout Southeast Asia. Although their geographic ranges overlap extensively, evidence of introgressive hybridization and mitochondrial DNA capture involving A. cinereus has only been reported in Singapore (and, more recently, Peninsular Malaysia), where maternal lineages of L. perspicillata appear to have disappeared. However, the timing of this event remains unclear. To investigate this issue, we analyzed the only museum specimen of a smooth-coated otter collected in Singapore, dating back to 1938. Genetic analysis revealed the first known individual whose maternal DNA matches the species identified through its physical characteristics. In addition, comparisons with genetic data from populations across the species’ range suggest that this individual may have originated from Peninsular Malaysia. These findings support the possibility that hybridization between L. perspicillata and A. cinereus is a relatively recent occurrence, although the conclusion should be treated cautiously because it is based on a single specimen. Broader genome-wide studies including both modern and historical samples from across Southeast Asia are still needed to clarify not only when this process began but also the underlying drivers. In Singapore, the phenomenon may be linked to the combined effects of urban expansion in nearby Peninsular Malaysia and local greening initiatives. Understanding this process is important for the conservation management of both otter species, which are currently classified as Critically Endangered in the Singapore Red Data Book.