- Fire is a common tool used in conservation areas across Africa to help regenerate grass for grazers, reduce encroachment of bushes, and control ticks and diseases. But how fire affects rhinos and their food has remained unclear.
- Researchers have found that black rhinos in Serengeti National Park prefer to graze in spots that burn just once in 10 years, and actively avoid areas that are burned frequently. The park’s managers carry out controlled burns at least once a year.
- The study found that fires reduce the availability of the plants that the black rhinos prefer to eat.
- The researchers have called for an adaptable fire strategy that allows burning in some areas to benefit grazers such as wildebeest and zebra, and avoids fires in rhinos’ preferred habitats.
When it comes to protecting the critically endangered black rhinoceros, the focus tends to be on preventing the animals from being poached. But insidious threats like fire could be affecting their long-term survival too, a new study warns.
In African savannas, natural resource managers frequently use fire as a tool to manage wildlife habitats; fire can help regenerate grass for grazers, reduce encroachment of bushes, and control ticks and diseases. But how fire affects rhinos and their food has remained unclear until recently.
T. Michael Anderson, an associate professor of biology at Wake Forest University, North Carolina, who has been working in Tanzania’s Serengeti National Park for decades, was especially concerned when six critically endangered eastern black rhinos (Diceros bicornis michaeli) were reintroduced to the park as part of the Serengeti Rhino Repatriation Project in 2010. The project aimed to bolster the dangerously low population of black rhinos in the park by moving in 32 rhinos over time.
“I had been doing research in Serengeti for nearly ten years at that point, so I was aware of the high frequency of fire in the national park,” Anderson told Mongabay. “It seemed that no one was talking about the potential costs or benefits of a high fire regime on the reintroduction effort of black rhinos.”
Anderson saw the reintroduction as an opportunity to seek some answers. Unfortunately, poachers killed four of the six introduced rhinos in 2011, and the Serengeti Rhino Repatriation Project stalled. This meant that the remaining rhinos would no longer be moved to the Serengeti.
So Anderson turned his attention to the only other black rhino population in the Serengeti, in the Moru region, south of the repatriation area. This population of about 40 rhinos has been relatively well-protected since the 1980s, Anderson said, and the area has a high fire frequency, making it an ideal place to study how fires affect rhinos. Moreover, the Tanzanian National Parks’ anti-poaching rangers follow the rhinos on a regular basis, taking detailed records of individual rhinos and activity patterns. These records represented a valuable source of data.
In analyzing these data from 2014 to 2016, Anderson’s team found that the black rhinos preferred to graze in spots that burn infrequently, or once in 10 years. The animals avoided areas that were burned frequently, the researchers report in their study published in Oryx. Park managers carry out controlled burns at least once a year.
“As a savanna ecologist, I was raised under the school of thought that fire improves forage quality for herbivores; in fact, several of my past scientific publications have demonstrated improved forage quality for grazers after fire,” Anderson said. “However, the spatial patterns of habitat use by the rhinos were clear: over several years they actively avoided areas of high fire frequency.”
The team dug deeper and found that fires reduced the availability of the plant species that rhinos prefer to eat. Of the hundreds of plant species that grow in the Serengeti, the rhinos eat only nine, most of which are nitrogen-fixing woody plants or forbs, a group of flowering plants. Fires destroy the above-ground portions of these plants.
The researchers suspect that for rhinos, which don’t typically forage on anything higher than 2 meters (6 feet), frequent fires can create “a ‘food desert’ in what on the surface looks like a savanna with abundant vegetation.”
“This may be limiting their capacity to increase their population size,” Anderson said.
How long the rhinos’ preferred plants take to regenerate after a fire still needs more research.
“Not all savanna plants tolerate fire equally,” Anderson said. “The Acacias (now Vachellia) all re-sprout after fire, but for some of the other N-fixing legumes that were highly preferred by rhinos — we just don’t know. One plant that I am very curious about and needs further research is Achyranthes aspera [one of the rhinos’ favorites]. Some sources, mostly websites about invasive plants, claim that it spreads with fire, but I often see it growing in habitats that resist burning or would not carry a fire because they are highly disturbed.”
What is clear, though, is that protected-area managers may need to rethink their fire management plans — employing a strategy that improves food availability and quality for both grazers like zebra and wildebeest, and browsers like rhinos. The researchers and Serengeti park authorities are now looking through data that the park rangers have collected over the past 20 years. These data can tell them how rhino habitats have changed over the long term in relation to fire.
Anderson and the park authorities have also been discussing ways to adopt a different fire management plan for different parts of the park, possibly suppressing fire in some regions and actively burning in the others.
“Implementing a diverse and adaptable management policy on the ground is incredibly challenging and takes time,” Anderson said. “Our collaboration is continuing, and the park authorities are very supportive of future research and data collection that will inform management about how to best increase black rhino habitat throughout the park.”
Citation:
Anderson, T. M., Ngoti, P. M., Nzunda, M. L., Griffith, D. M., Speed, J. D., Fossøy, F., … & Graae, B. J. The burning question: does fire affect habitat selection and forage preference of the black rhinoceros Diceros bicornis in East African savannahs?. Oryx, 1-10.