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Summer 2005
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GIS Applications for Gorilla Behavior and Habitat Analyses

By H. Dieter Steklis, Ph.D., Scott Madry, Ph.D., Netzin Gerald Steklis, and Nick Faust

  A Sabinyo gorilla
A Sabinyo gorilla.

As the sun sets over the Virunga volcanoes of central East Africa, the volcanoes' steep slopes and moisture-laden vegetation seem about as far away from modern technology as you can be on this earth. But scientists with The Dian Fossey Gorilla Fund International (DFGFI) are harnessing the power of advanced spatial technologies and GIS to help study the Virunga gorilla habitat and gorilla behavior and, ultimately, to preserve this endangered remnant population of mountain gorillas (Gorilla beringei beringei).

For the past decade, DFGFI scientists and collaborators have been studying the Virunga habitat and behavioral ecology of the mountain gorilla using images taken from space, GPS units to record gorilla movement and human activity, and historic maps. This data is then combined in a GIS to display and analyze the data for research and conservation purposes. The work of DFGFI is a pioneering application of these tools for primatology, and it has great potential for other conservation work throughout Africa and the rest of the world.

Collaboration began with a small United States Agency for International Development (USAID) grant to DFGFI for the creation of a digitized map of the Virunga volcanoes area. At first, this seemed to be a simple enough task, but it began a decade-long collaboration that has been a most interesting and challenging project for all involved.

  click to enlarge
The Virunga volcanoes image from NASA radar data over the digital elevation model created from Belgian colonial maps.

Several problems quickly emerged as the researchers began a search for existing maps of the three countries (Rwanda, Uganda, and the Democratic Republic of the Congo [DRC]) that comprise the Virunga area. No maps of Zaire (now the Democratic Republic of the Congo) were available, as there was a civil war underway in the region and possession of topographic maps or aerial photographs was politically sensitive. Unfortunately, the Zaire area accounts for more than half of the gorilla habitat. The best maps of Rwanda and Uganda were made in the 1950s and 1960s during the colonial era. In addition, it was clear that the Rwandan maps (produced by the Belgians and French) and Ugandan maps (produced by the British) were the products of their respective traditions; different mapping projections and coordinate systems were used, and the maps did not seem to match up at all when put together. Creating a unified regional map was clearly going to be more difficult than it first appeared.

DFGFI contacted the Belgian Royal Museum for Central Africa in Tervuren to see if there were any historic maps that could be used to fill in the missing Zaire (DRC) areas. In response, researchers received a complete set of 1938 1:100,000- and 1:50,000-scale maps of the region that had been produced by the Belgian Colonial Service. These maps covered the entire Virunga volcano range and surrounding area, so at least researchers had a start. These maps also served an important purpose by showing the region before modern development and population encroachment. These old maps came to serve as the researchers' "basemap," which is still, amazingly enough, the most recent comprehensive map of the entire area with significant detail.

GIS Applications

  gorilla resting in Virunga habitat
An endangered mountain gorilla resting in its Virunga volcanoes habitat.

DFGFI's first objective was to produce a three-dimensional digitized basemap that would serve as an important foundation for a variety of more sophisticated analyses concerning the relationships between the characteristics of the gorillas' environment and their behavior. Esri's ArcView software (and later ArcGIS) became the perfect tool for DFGFI's objectives, because it would allow researchers to merge data from many different sources, scales, and dates and recombine them in a powerful display and analytical environment.

DFGFI set about to digitize the various features from existing maps and to combine them in a GIS. Each contour from the 1938 Belgian maps was manually digitized to create a digital elevation model (DEM). This allowed the team to visualize the Virunga volcano region in three dimensions. They also extracted the main roads, political and park boundaries, hydrology, and other map features that were available, which would be used in future analyses of human impact on the habitat.

Habitat Classification and Monitoring

In order to generate accurate land-use and vegetation data for the Virunga region and to track habitat changes over time, DFGFI turned to satellites. Alas, another difficulty emerged—Gorillas in the Mist is more than the title of a book by Dian Fossey. Virtually all the satellite images were cloud covered. Many were clear except over the Virunga area due to the effect that the high mountains have on the microclimate. As a result, researchers searched for sources of satellite radar data, as these systems send their own burst of energy down to the earth and record the reflected energy, irrespective of cloud cover. The National Aeronautics and Space Administration was flying a research radar system on the space shuttle in 1994, so DFGFI arranged for the Virunga area to be imaged during the shuttle flight. This produced the first cloud-free remotely sensed view of the entire region and served to create an initial vegetation map. Not until January 2003 did DFGFI finally acquire a nearly cloud-free Landsat satellite image, and researchers used it to create a more accurate vegetation map of the region.

  click to enlarge
Vegetation classification of the Virunga volcanoes mountain gorilla habitat using the latest available Landsat data.

High-resolution (1 m) space radar imagery, such as provided by IKONOS, is particularly powerful for revealing the nature and extent of human impacts on the fragile gorilla habitat. In mid-2004, for example, within two months, approximately 6,000 farmers denuded approximately 15 square kilometers of prime gorilla habitat within the national park boundary. An international effort of government bodies and conservation organizations brought the destruction to a halt; although the farmers are gone now, the land still lies bare with the rows of cultivation clearly visible on the radar imagery. This type of imagery will prove important to the continued monitoring of the recovery of this habitat.

Patterns of Gorilla Habitat Use

With GPS receivers, DFGFI field staff members were trained to use GPS to log daily the gorilla group movements (i.e., nesting locations), from which group ranging patterns were established. Equally important, the DFGFI antipoaching patrols also recorded evidence of poaching activity. The GPS units were also used to map park boundaries and other major features in the area. Using small GPS units, this work is ongoing and provides researchers with the ability to include field observations directly into the GIS.

This GPS data gives DFGFI information on gorilla movements and poaching activity for recent years. However, to understand patterns over time that may be related to habitat changes or human activity (poaching), DFGFI needed to look back over decades. This means relying on DFGFI's store of archival maps, photographs, field notes, and other relevant data acquired in the field by numerous researchers, including Dian Fossey. For example, researchers digitized Fossey's hand-drawn maps of daily gorilla group locations, which allowed them to compare the current gorilla ranging patterns with those of 20 years ago. Their historic database is one of the longest sets of primate observations in the world and is ideal for revealing long-term patterns of habitat use.


  A Sabyinyo gorilla
A Sabyinyo gorilla.

The DFGFI goal is to understand the changing patterns of gorilla behavior and the gorillas' relationship to their environment and to quantify and understand the impacts of poaching and encroachment. There are many basic scientific questions that are still unknown, and the results of DFGFI's efforts should improve gorilla conservation practice. GIS allows researchers to combine all of the data that DFGFI has acquired (historic maps, aerial photographs, field observations, GPS locations, satellite images, and more) so they can begin to explore the data and ultimately test hypotheses in ways that were not possible only a decade ago. Another significant benefit of DFGFI's GIS database lies in the cumulative nature of DFGFI's field research. As field patrols continue and new research is conducted, the data is entered into the system, which constantly enlarges DFGFI's database and thereby enables researchers to compare data over time. Researchers can test hypotheses and track patterns in ways that are not possible using traditional field notes and hand-drawn maps.

An important part of DFGFI's mission is building scientific capacity in the region. Therefore, an aspect of its work is technology transfer to the countries comprising the Virunga region. For example, with a grant from the Georgia Research Alliance, DFGFI—in partnership with Clark Atlanta University, Georgia Tech, and the National University of Rwanda—established a GIS center in Rwanda that now serves as a successful, self-sustaining regional GIS research and training facility for a variety of applications in Rwanda and its neighboring countries. Such capacity building helps ensure local involvement in and commitment to long-term conservation.

H. Dieter Steklis, Ph.D., is with the Department of Anthropology, Rutgers University, and The Dian Fossey Gorilla Fund International. Scott Madry, Ph.D., is with the Department of Anthropology, University of North Carolina, Chapel Hill, and Informatics International, Inc. Netzin Gerald Steklis is with The Dian Fossey Gorilla Fund International. Nick Faust is with Georgia Tech Research Institute, Georgia Institute of Technology. For more information, visit DFGFI's Web site ( or Dr. Scott Madry's Web site (

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