The intermittent distribution of various animal and plant species in the world, has long been at the core of conservation biology and community ecology. It is therefore vital to know the processes and factors that impact rarities and endemism in the plant and animal world. The mechanism that regulates this rarity and limits a species’ distribution and abundance is still not fully understood. We are now beginning to understand that certain plants play an important role during periods of food scarcity. Generally, the plants that sustain animals during periods of food shortage are themselves not abundant (relative to other food trees), and during periods of food abundance, these plants may not be eaten at all. But Cullenia and Ficusspecies are the most sought after by the lion-tailed macaques and are important food resources throughout the year. Here we show how these much-favored food trees govern the distribution and very existence of this primate.