Chimps In Sierra Leone Have Learned To Cross Roads To Avoid Humans


Rachel Baxter

Copy Editor & Staff Writer


Over half of wild chimpanzees living in West Africa’s Sierra Leone live outside of protected areas. This means the apes are having to learn to survive in habitats devoid of forest and overrun with human infrastructure and cultivated land. The chimps have come up with various solutions, such as learning to safely cross roads and knowing when’s best to visit human habitats, but they’re still under threat.

Publishing their findings in the journal PLOS ONE, a team of researchers used hidden cameras to determine the abundance of chimps in an area dominated by farmland, swamps, and mangroves. They set up 24 camera traps over a period of eight months and created models to assess how human factors, like roads, settlements, and human presence, and different habitats shape chimpanzee abundance.


The team found that the best predictors of higher chimp abundance were distance from roads and proximity to swamplands. These factors were able to explain 43 percent of variation in chimp abundance. In contrast, chimp abundance didn’t seem to be affected by human presence, human settlements (both used and abandoned), or mangroves.

While humans don’t appear to deter chimpanzees from land, the researchers found that the two tend to avoid each other temporally, with humans being most active in cross-over areas in the central hours of the day and chimps showing up either early in the morning or late in the day.

However, the researchers warn that although chimps are learning to live with a fragmented habitat, for example by waiting for a safe moment to cross roads into one area of land to another or keeping a low profile when humans are most active, any further urbanization could significantly impact their numbers.

If habitat loss is very gradual and people tolerate their presence, chimps can survive, say the researchers. However, sharp increases in human activity and infrastructure would very likely lead to declines.


“If we want to secure their long-term survival, it is crucial that successful protection measures should benefit people and chimpanzees alike,” explained Dr Tatyana Humle, an expert in primate behavior at the University of Kent. “Conservation actions should focus on education and helping farmers to implement alternative agricultural methods to slash and burn farming and environmentally friendly revenue-generating activities to ensure coexistence between the two species.”

In West Africa, chimpanzees are critically endangered, threatened by a whole host of dangers such as disease, habitat destruction, poaching, and conflict with humans who share their habitat. The majority of these chimps live outside protected areas, making them much more vulnerable to the impacts of humans.

The researchers note that a potential solution would be to work with farmers to allow certain areas of farmland to return to forest refuges, which would be managed by the community. This would create natural corridors and allow both chimps and other wildlife to traverse between areas of desired habitat in safety.