Surveys and Ecological Research

Measuring distances along forest transects

To date, less than 30% of the bonobo range has been surveyed (Bonobo Conservation Strategy 2012-2022). Therefore, one of the most urgent conservation needs is to find out how many bonobos exist in the wild and where they live. Before BCBI’s first field surveys in 1997, scientists speculated that bonobos did not exist in the Salonga National Park. Our original surveys were among the first to elevate the conservation community’s awareness of the national park as a priority site for bonobo conservation. Today, the Salonga is recognized as a centerpiece for bonobo conservation. It is the only place in the Democratic Republic of Congo where bonobos and elephants still occur together in substantial numbers and where natural forest dynamics can still be studied.

Salonga National Park

Collecting elephant dung samples for genetic analysis

Our surveys in the Salonga National Park concentrate on:

  • Determining bonobo and elephant distribution and abundance– where these species occur within this huge park and what their population size is;
  • The ecological factors that determine bonobo distribution and abundance, such as the forest characteristics that are associated with bonobo nesting;
  • The impact of hunting on animal distribution and population size; and
  • The degree of population fragmentation: what ecological or human parameters may determine population limits.

Surveys mostly consist of observers following straight compass lines through the forest and counting the number of bonobo nests and elephant dung piles observed/encountered along the length of each transect. Using standard transect methodology (DISTANCE or variable-width), we estimate the density of both bonobos and elephants (Buckland, et. al 2001). Observers also count the number of human signs pertaining to illegal hunting (snares, cartridges, trails, camps, etc.) found along transects. Upon analysis, we examine the correlation between animal vs. human signs. Lastly, as observers walk along transects, they note the forest type so that we can estimate the proportion of each forest type sampled within the area. In this way, we can determine whether bonobos nest more frequently in a given forest type (Reinartz, et al. 2006).

The results of our surveys over the past decade have highlighted several significant trends. They suggest that:

  • Salonga is composed of at least 11 discernible forest types (excluding true swamps).
  • Bonobo nests are not randomly distributed throughout the forest or among all forest types. In the Salonga, forest structure and composition appear to be important ecological features influencing population distribution and density, especially in areas with little to no human activity. Bonobos tend to nest most frequently in mixed mature forests on terra firma soils, in forests with a predominantly Haumania (Marantaceae) understory, and to a lesser extent in forests with woody understory.
  • There does not appear to be a correlation between elephant-sign occurrence and forest type.
  • Both bonobos and elephants occur in areas with less human activity.
Surveys and Ecological Research
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of surveys and ecological research.

Today the BCBI field team is intensively surveying bonobos and elephants in the strip of land between the Yenge and Salonga Rivers, known as the Watsi Kengo Sector (6,664 km2). We survey the forest along compass lines that are 4 km apart in order to determine whether there are gaps in the species’ distributions within this area and to test our initial findings that certain forest types are favored by bonobos for nesting. These data will refine predictive models to detect areas of probable bonobo occurrence (Reinartz et al., 2008). Moreover, the survey will estimate bonobo and elephant density in the corridor and provide updated baseline data for future population monitoring. Of immediate importance, these surveys identify bonobo, elephant and poaching hotspots. They inform ICCN where to target park management and anti-poaching activities. Finally, the survey data will add to the A.P.E.S. database of geographically referenced bonobo occurrences. This dataset will better define the meta-population of bonobo distribution in the national park and in the country.

During surveys, ICCN park guards from the Etate Patrol Post play a critical role. They join the BCBI research team, help identify animal signs, secure the survey area, and practice their skills in navigation/wildlife monitoring.

Other Sites in DRC

Lomako Cadjobe Corridor

Taking notes
Two women were among the 20 volunteer trainees.

While BCBI works mainly in the Salonga National Park, we occasionally have an opportunity to work in other areas important to bonobo conservation. This gives us a chance to compare regional environmental influences on bonobo occurrence. One notable opportunity occurred in 2009, when BCBI researchers surveyed bonobos in the Cadjobe Corridor, a ~1,700 km2 block of community-owned forest near the Lomako Yokokala Faunal Reserve in Maringa-Lopori-Wamba CARPE Landscape.

At the invitation of the African Wildlife Foundation (AWF), BCBI trained local residents in survey and bio-monitoring techniques so that they had the skills and understanding to participate in the survey of their community forest. This project was funded by the U.S. Fish and Wildlife Service Great Ape Conservation Fund, AWF, and the Zoological Society of Milwaukee.

The surveys provided the following information about bonobo density, hunting activity and forest types in the corridor:

  • We estimated that about 500 adult bonobos lived within the survey area.
  • Bonobo distribution was confined to a remote central strip of forest far from the Lomako and Lonkomo Rivers, where major human settlements occurred.
  • We found frequent hunting signs throughout the study area.  In areas of intense hunting activity, bonobo occurrence was significantly less. Large new agricultural tracts gradually reduced the perimeter of the forest and provided greater access for hunting.
  • Approximately 80% of the forest types in the corridor was mixed mature forests containing about equal proportions of Haumania (Marantaceae) and woody understory.

We concluded that bonobos were highly threatened in the corridor and faced the possibility of extinction if hunting was not soon brought under control. One obstacle to control hunting was a common belief by the local people that bonobos were plentiful. However, as BCBI staff trained the community members and gave them the skills to collect and interpret data, the members began to objectively gauge the status of bonobos and other wildlife in the forest. They came to realize that the bonobo could not survive long under present hunting pressures. Thus, their work and the process of self-discovery informed community decisions to consolidate their groups and formulate a system of bonobo protection and monitoring. Because of its bonobo population, the communities working with AWF recognized the Cadjobe forest as an important wildlife corridor connecting bonobo populations to others throughout the landscape’s maze of human settlements.

A copy of the full report is available upon request.

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