Eastern Himalaya

Mammal seed dispersal project

Seed dispersal- an essential process

In tropical forests, most woody plants are dispersed by fruit-eating animals (frugivores). By dispersing (and sometimes destroying) seeds, frugivores can directly impact the diversity, structure and evolution of plants; therefore, these mutualisms are essential for ecosystem function. Seed dispersal interactions are dynamic given the changing population densities of key mutualists in response to disturbance: many vulnerable species are declining in abundance, while more robust species can maintain or possibly increase their populations.

The seed dispersal roles of these diverse assemblages are essential to understanding the drivers of variation in plant recruitment and fruit morphology, as well as predicting future scenarios for forest maintenance in the face of ongoing anthropogenic disturbances. Yet, we still have a poor understanding of the reliance of trees on seed dispersal by key frugivore mutualists.

Mammals- understudied seed dispersers:

Frugivores differ in their fruit choice and seed dispersal capability; therefore, the many studies on seed dispersal by birds and primates are not useful in understanding the roles played by less-studied frugivores. For example, carnivores and herbivores are important seed dispersers in temperate regions, but studies in diverse tropical forests are limited to just a few species. Also, squirrels act as seed dispersers and seed predators in the diverse tropical forests, However, the degree of their seed dispersal and seed predation role has not been assessed in detail. This research gap is essential to address for several reasons. First, many species have large-body sizes indicating they could fulfil unique dispersal roles by dispersing many seeds, particularly large-seeded species which lack alternative mutualists. Second, fruit-eating herbivores and squirrels appear to have variable roles, so data must be generated for a broad range of plant species, to identify plant traits that determine their mutualistic or antagonistic roles. These data would allow broader predictions on mutualistic roles across the community. Third, many of these species are either globally threatened or common, which has important implications for community-level roles.

Community-level approach

This study will provide critical information on the ecology and natural history of woody plants in the region, which will be used to promote plant and habitat conservation. By identifying key fruit and seed traits that influence the likelihood of successful dispersal by carnivores, herbivores, and squirrels, we can predict interaction outcomes at the community-level and, also, predict the consequences of the ongoing defaunation of large and medium-bodied animals for the large-fruited species which potentially rely on them for dispersal.

Study species-

For at least 14 plant species, we will document frugivory and seed dispersal in carnivores(civets, martens, bears), herbivores (sambar, barking deer, elephant, wild boar) and squirrels(Pallas’s squirrel, hoary-bellied Himalayan squirrel, Malayan giant squirrel) in Pakke Tiger Reserve, Arunachal Pradesh. Other frugivorous mammals that play important roles in seed dispersal for these tree species will also be studied. The seed dispersal effectiveness framework (SDE) will be used to measure the quantity and quality of seed dispersal, and frugivory, by the mammal groups.

Barking deer