Eastern Himalaya

Rats, seeds and rainforest trees

Plant-animal interactions: seed predation and plant demography

Forest rats love to eat seeds. Some of them also move seeds and collect them as future food supply. How far are rodents able to carry the seeds? Do rodents always remember to eat everything they store? What happens to the seeds that are forgotten? To find out, we tracked the movement of seeds fallen on forest floor.

To eat today or tomorrow?

The interactions among different living organisms fit, much like a jigsaw puzzle, in a complex but structured forest community. We explored the scope and nature of interactions that exists among rainforest trees and a lesser-known group of animals, the terrestrial forest rodents. Rodents seek out plant seeds as an immediate food resource (seeds are eaten as soon as they are discovered) or as a future food resource (seeds are stored or ‘cached’ for later consumption).

We followed seed fates of 10,777 seeds belonging to ten different evergreen tree species by exploring effects of distance from parent tree and density of conspecific seeds. Our results showed that overall seed removal was higher than on-site predation by rodents. There were differences in seed handling behaviour between rodent groups. Murid rodents were more likely to remove and cache seeds while porcupines were more likely to indulge in onsite predation. Interestingly, a true cricket Brachytrupes sp. was also documented caching seeds of three tree species. Hard seeds were more likely to be removed and cached while soft seeds were more likely to be preyed upon.Seeds were moved up to 19m from the parent tree. Approximately 12% of the cached seeds germinated, indicating that seed removal behaviour could play an important role in reducing the competition between conspecific tree species during reproduction.