Seed dispersal within Southern White Rhinos (Ceratotherium simum simum)
Rhinos are widely recognized as a keystone species for several reasons. Let’s explore why they play such a crucial role in their ecosystems. Rhinos are mega herbivores, which means they consume a substantial amount of vegetation. For instance, the southern white rhino eats approximately 50 kg of grass daily. This extensive grazing helps maintain grasslands by preventing overgrowth and promoting new grass growth. If grass is not consumed, its nutritional value declines, and after about three to five years without breakdown, it can release more carbon dioxide into the atmosphere than if it were burned.
When rhinos consume grass, it passes through their digestive systems and is broken down into fertilizer, enriching the soil with nutrients. This process supports the growth of nutrient-rich grass, which helps other grazers build strong fat reserves to survive the winter months.
But what about the seeds that rhinos consume? As hind-gut fermenters, rhinos do not have four stomach chambers like cows and do not regurgitate their food. Instead, they use their lips to break off grass, chew it, and swallow it. The grass then sits in their stomachs, where microorganisms help break it down, allowing the rhino to absorb the nutrients. This digestive process enables more seeds to pass through the rhino, potentially aiding in seed dispersal.
Research on Greater one-horned rhinos have shown that 80% of the seeds they consume are spread within a square kilometre. Since Greater one-horned rhinos are mixed feeders, they consume different seeds that may require an animal for germination, like how elephants disperse marula seeds. Similar observation is with Sumatran rhinos, with less than 80 individual remaining in the wild, a few plant species on the Indonesian islands of Sumatra and Borneo are threatened. As these rhinos are mega frugivores that eat large fruits, they can disperse seeds over kilometres. However, with the decline of these rhinos, we are also witnessing a decrease in certain flora species.
This study aims to confirm the baseline assumption that rhinos disperse seeds and, once confirmed, to determine the extent of grass seed dispersal through rhino dung. Rhino dung is typically solid, and it is believed that nothing will grow directly from it without assistance in breaking it open. Dung beetles are the most common species to break down rhino dung quickly, rolling it into balls. Some birds also break open the dung, whether they are seed-eating or insect-eating.
Since dung beetles are seasonal, and dung breakdown is slower during drier seasons, we need to investigate what happens to the seeds consumed during these periods. This leads to our second question: do rhino middens have significant environmental impacts? We know that rhinos use middens to leave messages for other rhinos in the area. These dung piles contain multiple messages, but could they also serve as a seed bank for grass species?
Through this study, we aim to determine the importance of rhinos within an ecosystem and identify the species of grass they consume. This information will help us understand which types of grass to cultivate to ensure that rhinos receive the best nutrients throughout the year. Additionally, we hope to identify the best grass species for all grazers throughout the year. Furthermore, we can assess whether rhino middens could be an effective tool for soil rehabilitation in acidic or similar soil types. This could allow us to replant grass that originally occurred in the area, similar to current practices with cattle.
Summary
Resesarch Question
1. How many seeds are present in rhino dung?
2. What species of grass are found in the dung?
3. What animals are found in rhino dung, and what are their functions?
4. Do rhino middens serve as a seed bank?
- Can they be used to determine the species and biodiversity of grass richness in the ecosystem?
- Can the dung from the middens be used to restore barren soil?
- How long can grass seeds remain dormant?
5. What types of seeds can be found in black rhino dung?
Method of Measurement:
Sample Collection:
Collect samples from every rhino midden to assess the presence of a grass seed bank.
For white rhinos, gather 2 to 3 dung samples weekly from different areas within their habitat.
Sample Preparation:
Break apart each dung sample and soak it in water for one hour.
Strain the water to separate the solid remnants.
Mix the remaining solid material with potting soil to prevent contamination from other seeds.
Monitoring and Growth:
Monitor the mixed samples closely for germination.
Identify and document any grass species that emerge.
Continue this monitoring process for a minimum of one year to account for seasonal variations.
Black Rhino Dung Analysis:
Wait for shrubs to produce fruit or seed pods before collecting black rhino dung samples.
Use a similar method as with white rhinos: break apart the dung, soak in water, strain, and mix with potting soil.
Attempt to identify the flora species from the seeds present in the dung where possible.
Data Analysis:
Record the types and quantities of grass species that germinate from the dung samples.
Compare the germination rates and species diversity between samples collected in different seasons.
Analyze the role of dung beetles in breaking down dung and facilitating seed dispersal, particularly during the rainy season.
Study Benefits:
This study aims to determine the importance of rhinos in ecosystems and how much they contribute to seed distribution. Understanding their role could reveal whether rhinos are a key species in restoring flora within ecosystems. As we strive for more sustainable practices globally, it is crucial to restore habitats to their natural states.