There Is No Substitute For Elephants As Seed Dispersers

Asian tapirs are no elephants

In light of the situation, the research team evaluated the seed-dispersing capacity of another large herbivore weighing 300 kg. For cultural reasons it is not hunted and has a similar digestive system to that of elephants and rhinoceroses: the Asian tapir (Tapirus indicus).

The study allowed researchers to analyse the effect of dispersion by tapirs on the seed survival of nine different plants. This included some large plant species such as the mango tree and durian, as well as other smaller species like the ‘elephant apple’ (Dillenia indica).

Among other outcomes, the results show that tapirs defecated 8% of the tamarind seeds ingested (none of which germinated) compared to elephants, who defecated 75% of the 2,390 ingested seeds (65% of which germinated).

“The Asian tapirs spit, chew or digest the majority of large seeds. This either destroys them or leaves them in the same place. As a result, they are not good dispersers for plants with large fruits and seeds,” confirms Campos-Arceiz. In this sense, “given the role that they play they belong to a different group to elephants and rhinoceroses.”

Stopping illegal hunting is the priority

“If these megaherbivores disappear from the ecosystem, their contribution to ecological processes will too be lost and the path of the ecosystem will change irreversibly,” explains the lead author, who goes on to state that “the most probable consequences are the change in the structure of the undergrowth and the forest and the loss of certain species.” Elephants and rhinoceroses play a unique ecological role that cannot be replaced by other species.

Without large herbivores, new large seed plants will always grow in close proximity to the mother plant and are therefore “unable to colonise available space in other forest areas,” warns the IMEDEA researcher.

In this respect, those species that depend on large animals will become increasingly rare whereas those that depend on the wind and smaller, abundant animals will increase in terms of density and dominance. Campos-Arceiz asserts that “at the end of the day, the composition and structure of the forest changes and ends up becoming less complex on a structural and functional level: this translates as a loss of biodiversity.”

To avoid such a scenario, researchers suggest that megafauna should be protected and in some cases megaherbivores should be reintroduced into areas from where they had previously disappeared. “In the south-east of Asia, the priority is to stop illegal hunting and mitigate the impact of habitat loss,” indicates the expert, criticising the “absurd” motivation to kill in order to sell their horns and tusks for traditional medicine (“with no therapeutic benefits”) or to make ornamental products. This also highlights the need to combat illegal trade in a “much more determined way.”

Read more at: http://phys.org/news/2012-05-absence-elephants-rhinoceroses-biodiversity-tropical.html#jCp