The relationships between animals, plants, their habitat, humans and the planet as a whole are complex and we are only starting to understand these connections. What is clear, however, is that wildlife play a key role in maintaining the health of their forest habitats, even in helping to restore a forest after natural processes threaten the land.
During a field study in Chitwan National Park in Nepal, I started to look at individual species and the ecological services they provide to sustain the forests. I found that boars, bears, birds and bats in particular play a key role in the health of the forests here.
First it’s important to understand both the natural processes and also how the landscape changes across geography:
- Narayani River and Rapti River, along with many small rivulets, pass through the Chitwan National Park. Every year during the rainy season the rivers are flooded and they inundate the nearby river banks. I have heard in the night the sound of large Sal trees being uprooted by the current of these rivers. Rivers also inundate the grasslands and force sand hills to build up on the banks, converting the rich nutrient grassland into barren sand land.
- Chitwan National Parks contains dense forests and large grasslands that together support a diverse community of mammals. And there are also different partially barren sand banks where one can see the changes in the habitat. The banks near the river start with shorter grass that gets taller and denser as one walks away. Moving further one can see the small saplings of Sal trees sprouting from mud and sand.
What I have seen is an incredible natural process in restoration and health: that bear and wild boar create suitable landforms by ploughing and digging. Nutrients gets mixed together as leaves brought by winds get trapped and upper crust soil gets mixed with lower soil. Bats and birds then sow seeds in these landforms and clouds pour water on them. Thanks to this set of relationships, seeds can come out of the ground strong and resilient, providing a home to the species that helped to sow them.
The following are just some of the species that play a role in improving ecosystem health and supporting some of the natural changes in Chitwan National Park, where I conducted small mammals’ surveys:
Wild Boar ploughs the land in many parts of forest, doing so while searching for food. In the mid hills of Nepal, wild boar is actually considered a pest that can destroy many hectares of land in a single night, sometimes resulting in the loss of food supply for a family for a year. This seemingly nuisance behavior in a human-dominated landscape, however, can be a crucial factor for maintaining the forests of Chitwan National Park. As a natural plougher, the wild boar ploughs the upper crust of the forest. As a result, minerals get mixed together necessary for sowed seed to sprout in loose soil, increasing the probability of plant survival. Only one species of wild boar is found in the park. Pygmy hog once found has not been recorded in the park for years and is thought to be locally extinct.
Bears, such as Sloth Bears in Chitwan National Park, often dig a burrow while searching for food. I frequently saw large holes in the middle of nowhere during a jungle walk in Chitwan National Park and could easily identify them as bear work. I remember from my childhood that whenever I used to plant trees with my father, he used to dig a burrow, tear off the plastic covering the roots of plants bought from the nursery and plant it. We used to fill half the burrows with cow dung (as a fertilizer) and then sow the sapling. My father would tell me that the bigger the burrow, the higher the chances of survival of the plant. It seems the bigger burrows in the forest are even more useful, protecting novice saplings from herbivorous grazers on the ground level. As the plants reach the surface, they are more mature and better able to survive the snout attacks of ungulates and recover quickly.
Once the ploughing and digging of burrows are completed on the ground, these flying angels do their job. Birds feed on fruits, partially digest their seeds in their guts and then defecate wherever they feel like it. Seeds from bird guts are actually more efficient in sprouting than the seeds directly falling on the ground. Also, birds move large distances, which helps in distributing the seeds from various plants of different areas. This also helps to maintain the diversity within the landscape ecosystem. There are currently more than 500 species of birds recorded from the Chitwan National Park. Giant Hornbill, Black Bulbul, Grey Wagtail, Lesser Caucal are some of the birds responsible for seed dispersal.
These dark knights play a similar role to birds and are equally important as they silently do their job in the night. Bats also feed on the fruits of a variety of plants and help to distribute the seeds as they defecate. They are also responsible for the pollination of night-flowering plants. Ecosystems never sleep and the job gets done during the day and night. Flying Fox, Dawn Bat, Greater Short-nosed Fruit Bat and Leschenault’s Rousette are four species of bats dispersing seeds in Chitwan National Park.
Knowing how these relationships works can help the Department of National Parks and Wildlife Conservation manage habitat within the park. Without bears, boars, bats or birds, we know that Chitwan National Park would not be able to recover, grow or thrive. And that would be a tremendous loss to our planet.
(Top photo: The typical habitat of Chitwan National Park. Photo by Sagar Dahal)