Rhino plays crucial role in forest expansion: Study

Kathmandu, Aug. 11: The jungles of Chitwan and Shuklaphanta National Parks are home to a variety of wildlife. While these places are threatened by human encroachment, the greater one-horned rhino plays a crucial role in forest regeneration. 

A recent study has shed light on rhinos' unique seed dispersal functions. When rhinos consume fruits from plants like Mallotus nudiflorus (rhino apple), they play the role of gardeners.

“As they roam the areas of their habitat, the seeds they have ingested pass through their digestive system and are deposited miles away from where they were first eaten. This process, known as seed dispersal, is vital for forest regeneration,” said Balaram Awasthi, lead researcher of “Seed dispersal effectiveness by greater one-horned rhinos and domestic bovids of a megafaunal fruit.”

According to Awasthi, Assistant Professor at Siddhanath Science Campus, Tribhuvan University, the research was conducted from 2020 to 2021 within Chitwan and Shuklaphanta National Parks to find out the seed disbursement of megafauna. Domestic cattle (like cows and buffaloes) can help maintain populations of a particular tree species, M. nudiflorus also called vellor in Nepali, by spreading its seeds. 

However, the seeds they disperse do not travel as far as those dispersed by wild animals like rhinos. The distance seeds travel is important because it affects how many places the seeds can reach and whether they can grow into new trees, Awasthi said. 

The study also found that rhinos are very good at spreading seeds over long distances, similar to elephants. But unlike elephants, rhinos eat fruits of vellor and were the main animals spreading these seeds in the Tarai floodplains over 200 years ago. When rhinos disappeared from many areas, it likely had a negative impact on the vellor tree populations because fewer seeds were being spread far enough to grow into new trees, he said.

The research, conducted in the Tarai Arc Landscape of Nepal, found that rhinos are particularly effective at dispersing seeds over long distances, often more than a kilometre, with some seeds being carried as far as 5.4 kilometres. 

This long-distance dispersal is essential for the spread and growth of many plant species that would otherwise struggle to propagate. 

But what happens if these majestic creatures are driven to extinction? he asked. With the rhino population in constant danger from poaching and habitat loss, scientists are keen to explore whether other animals can step in to fill the gap left by the rhinos.

In the study, the researchers conducted experiments and collected data on the feeding habits, seed germination, and movement patterns of greater one-horned rhinos and domestic cattle (like cows and buffaloes) in Chitwan and Shuklaphanta national parks in Nepal. 

The goal was to see if domestic cattle could effectively replace rhinos in spreading the seeds of a tree species that relies on rhinos for seed dispersal.

The results, however, were serious, he added. While cattle and buffaloes do disperse seeds, they are nowhere near as effective as rhinos. 

Cattle, for example, were found to disperse only 20 per cent of seeds over distances greater than 1 kilometre, with a maximum dispersal distance of about 2.2 kilometres. 

Buffaloes fared even worse, with just 15 per cent of seeds dispersed over 1 kilometre and a maximum range of 1.4 kilometres. Likewise, the seeds dispersed by these domestic animals had lower germination rates compared to those dispersed by rhinos.

Without rhinos, the dispersal of seeds that are crucial for forest regeneration would be severely reduced. Over time, this could lead to a decline in forest diversity and health, as certain plant species fail to spread and reproduce effectively. The disappearance of these plants would have a cascading effect on the entire ecosystem, impacting everything from the smallest insects to the largest predators, the author said. 

In essence, rhinos are unique when it comes to maintaining the balance of their natural habitat. They are the silent gardeners of the forest, ensuring that the next generation of plants takes root and flourishes.

The study’s findings highlight the urgent need to protect and preserve rhino populations. Conservation efforts are not just about saving a single species but they are about safeguarding entire ecosystems. The health of Nepal’s forests depends on the continued presence of these magnificent creatures, Awasthi said.

“As we confront the growing challenges of climate change and biodiversity loss, it is crucial to recognise the interconnectedness of all life forms. The extinction of a single species, like the rhino, could trigger a domino effect, leading to unforeseen consequences for our planet’s ecosystems,” he said

Noted conservationist Shant Raj Jnawali said that rhinos play a major role in dispersing seeds along the banks of the Rapti and Narayani Rivers as well. “Sometimes we can see clusters of vellor saplings growing in areas where rhinos have defecated,” he added.

The fruit of vellor also has medicinal value for rhinos, he added. It helps cleanse their stomach and remove tapeworms, as evidenced by the presence of many tapeworms in their faeces.