Demography and birth seasonality in the Nicobar long-tailed macaque (Macaca fascicularis umbrosus)

Abstract

The Nicobar long-tailed macaque (Macaca fascicularis umbrosus) is confined to the southern and central Nicobar archipelago. We have collected demographic and birth data for five groups of M. f. umbrosus to understand their group structure, demography and breeding seasonality. Group size, individuals in age- sex classes and age-sex ratio did not vary between the groups and years. The birth rate was neither associated with the number of adult females in the group nor with group size. The number of births in a month was positively correlated with rainfall, and about 71% of the births occurred during the rainy season, though, the number of births did not vary systematically among the months. Perhaps, higher availability of food resources in the wet season than the rest of the year may support lactation in females and provide food for the weaned infants. The similarity in some demographic traits between the Nicobar long-tailed macaque and other subspecies indicates that these traits may be conserved over evolutionary time, while for other traits, differences among subspecies may reflect the effect of local conditions and recent histories. This is the first report on demography and birth seasonality of this unique subspecies of the long-tailed macaque.