It was the dry season of 2006 in Tanzania, Africa. Across a landscape that varies from vast savannah to steep hillside to dense, wet forest, Clinton Epps and his science team trekked more than 400 miles on foot. He, Lauren Gwin and students from Tanzania’s Sokoine University battled intense heat and thieves who attempted to steal their research equipment. At every community, they stopped to meet with local officials and hire guides. They weren’t about to be deterred.
The focus of their two-year study was animal migration patterns in a country that is larger than Texas and Oklahoma combined and whose rising human population has forced wildlife into a diminishing network of reserves. With no fences, the elephants, giraffes, antelope, lions and other species ignore human boundaries as they travel from one reserve to another. As farm fields encroach on habitat and roads create barriers to travel corridors, wildlife struggles to maintain a foothold.
Epps was focusing on patterns of elephant movement between reserves. Despite all the time spent in the field, he and his team saw the seven-ton animals outside these designated areas only once. But the evidence they did find — dung, tracks in the dirt — would prove to help them and other researchers understand where elephants are traveling and whether or not the human competition for space is fragmenting the elephant population.
“I was interested in connectivity and movement between reserves as a general research topic, and this was a landscape where that work was needed,” says Epps. He and Gwin now work at Oregon State University where Epps is an assistant professor in Fisheries and Wildlife and Gwin is a research associate in Agricultural and Research Economics.
As a Ph.D. student at U.C. Berkeley, Epps had studied bighorn sheep movements in California’s Mojave Desert. In Africa, he could apply his knowledge to a new system. His goal is to better understand animal migration pathways with the hope of guarding them from human encroachment. Today, he and Rachel Crowhurst, an OSU graduate student, are doing this by analyzing animal tracks and DNA from fecal matter.
Drawing on his knowledge of bighorn sheep, Epps analyzed elephant tracking data to map out specific corridors of movement. Although elephants are elusive during the day, the scientists’ analysis shows that the animals still appear to be traveling somewhat freely between the reserves. While some environmental factors such as steep slopes influence elephant travel choices, human activity appears to be the most significant constraint.
“Elephants are a good indicator species,” he says. “Species that are the best predictors at this scale are generalists and most sensitive to human activity.”
Based on the data received from the elephant study, scientists now have a better understanding of the distribution of many major mammal species in central Tanzania.
A History of Humanity
“These are places where there have been people, we think, as long as people have been around,” Epps says. But in recent times, the number of inhabitants has grown exponentially, increasing strain on an already tense relationship between humans and nature. In 1955, there were nine million people in Tanzania. By 2008, the population had skyrocketed to 42.5 million, with agriculture overtaking the grasslands.
In the mid 1900s, humans were forced out of the areas currently designated as reserves. Epps says that during his studies, he regularly comes across human artifacts. “I think this is something conservationists tend to oversimplify. These reserves have not always been free of human occupation,” Epps says. “What has changed, I think, is the sheer density of the human population and the intensity of that footprint.”
From Tent to Lab Bench
As he was completing his field data collection in Tanzania, Epps was hired at OSU. With financial support from the university and from the National Science Foundation, he has begun analyzing DNA from fecal matter to determine the specific corridors of elephant movement.
By combining elephant tracks with the information gathered from DNA samples, Epps has been contrasting long-term and modern-day elephant movement patterns in the presence of human constraints. In addition, the information from the DNA is giving valuable insight into the diversity, or lack thereof, among the elephant gene pools.
“There’s not much genetic structure on the scale of Tanzania, which tells you that there have been elephants moving all over the place (through corridors),” Epps says. Limited genetic structure implies that distinct populations didn’t exist within areas now established as reserves, suggesting the animals historically have been interbreeding throughout the country.
Giraffes and Antelope
In 2011, Crowhurst spent five months of intensive studies on other large mammal movement in Tanzania, including giraffes and two species of antelope. Together, their data will help give a better picture of animal connectivity in Tanzania and raise the possibility of preserving corridors and reducing conflicts between humans and wildlife.
“By comparing connectivity patterns across a range of species, we can implement management schemes that will have a higher probability of maintaining or enhancing connectivity for most wildlife species,” Crowhurst says.
While the results are helping identify areas at risk, time is running out in some locations. For example, Epps and collaborating scientists were able to identify a highway crossing that provides elephants with critical access between reserves, connectivity they need to associate with other elephant populations. “It’s possible that this spot is the remaining link between gene flow for this whole area,” Epps says.
Now that this possible bottleneck has been identified, Epps and Crowhurst hope that accommodations can be made to sustain these wildlife movements. Since most land is privately owned, the government will need to work with landowners to achieve a balance between wildlife and people. For elephants, a species that is slowly recovering from the ivory trade and is battling human expansion, the effects of this barrier are unpredictable.
Back in a lab at OSU, Epps and Crowhurst continue to examine data from their samples and their tracking records. Together they are slowly mapping the diverse Tanzania landscape and helping ensure that despite human expansion, some of it will remain wild.