Cullenia exarillata is a dominant tree species in the mid-elevation tropical rainforests (between 700 and 1,400 m elevation) of the southern Western Ghats. It is also among the most abundant canopy trees in relatively undisturbed mature wet evergreen forests. Individual trees were estimated to produce between 1300 and 26000 flowers (average = 8734) chiefly between February and May, followed by a fruiting peak between May and September, in a rainforest in the southern end of the Western Ghats. As the tree flowers abundantly during the dry season, a period of fruit scarcity in the forest, the flowers attract many diurnal and nocturnal frugivorous mammals and birds, making the tree a possible keystone species in these forests. The flowers are low in nectar but contain fleshy sepals embedded with nectaries which are the main reward for animal visitors. The flowers are eaten by endemic arboreal mammals such as Lion-tailed Macaque and Brown Palm Civet. The seeds and flowers of this species form a major part of the diet (20.7% of annual diet) of Lion-tailed Macaque in mid-elevation rainforests of Silent Valley National Park. A seed predation rate of 45% has been estimated in a wet evergreen forest of the southern Western Ghats, caused by species such as Indian Giant squirrels that feed on unripe fruits (with softer spines) and Lion-tailed Macaques that feed on ripe fruits (with hard spines).