Gemini calling! First occurrence of successful twinning in wild, endangered lion-tailed macaques Macaca silenus in the Anamalai hills of the Western Ghats, India

We recorded the first occurrence of surviving twins in lion-tailed macaques Macaca silenus from the Anamalai hills of the Western Ghats, India. The Puthuthottam population of liontailed macaques has historically been restricted to a rainforest fragment measuring 92ha, situated adjacent to human settlements, however, direct interactions between macaques and humans have been observed only in the last ten years. The population now visit settlements at a rate of 0.52/ day, and exploits anthropogenic foods. We recorded two sets of twins from the Puthuthottam population within a six-month period. Two previous cases of twins have been observed in this population since 2000, however, in both cases the twins did not survive beyond a few weeks. We followed and opportunistically collected ad libitum behavioural data on both sets of twins for a year between March 2019 to March 2020. Both mothers carrying the twins used the ground substrate extensively, however the mother with the younger set of twins also used the canopy and other precarious substrates such as cable wires. Our report shows that twinning occurs in lion-tailed macaques and twins are able to survive successfully. This report also supports previous evidence that twinning may occur in higher frequencies as a direct response to provisioning, with the mothers’ behaviour contributing to the successful survival of both twins.