Wild chimpanzees on the edge: nocturnal activities in croplands.

Sabrina Krief,Andrew Seguya,Sarah Bortolamiol,Marie Cibot,Jean-Michel Krief,Shelly Masi,Roscoe Stanyon

doi:10.1371/journal.pone.0109925

Abstract

In a rapidly changing landscape highly impacted by anthropogenic activities, the great apes are facing new challenges to coexist with humans. For chimpanzee communities inhabiting encroached territories, not bordered by rival conspecifics but by human agricultural fields, such boundaries are risky areas. To investigate the hypothesis that they use specific strategies for incursions out of the forest into maize fields to prevent the risk of detection by humans guarding their field, we carried out video recordings of chimpanzees at the edge of the forest bordered by a maize plantation in Kibale National Park, Uganda. Contrary to our expectations, large parties are engaged in crop-raids, including vulnerable individuals such as females with clinging infants. More surprisingly chimpanzees were crop-raiding during the night. They also stayed longer in the maize field and presented few signs of vigilance and anxiety during these nocturnal crop-raids. While nocturnal activities of chimpanzees have been reported during full moon periods, this is the first record of frequent and repeated nocturnal activities after twilight, in darkness. Habitat destruction may have promoted behavioural adjustments such as nocturnal exploitation of open croplands.

Highlights

Compared to previous centuries, the level of demographic pressure and the rate of habitat loss for wildlife caused by humans have dramatically increased [1]
To test the hypothesis that chimpanzees may have developed several strategies to survive in highly disturbed habitats and to avoid detection by humans, including being active during moonlit nights, we focused our survey on a maize field bordering the forested area of Sebitoli in the northern part of Kibale National Park (KNP), Uganda
Study site Kibale National Park (795 km2) is a medium-altitude moist tropical forest located in Western Uganda

Summary

Introduction

The level of demographic pressure and the rate of habitat loss for wildlife caused by humans have dramatically increased [1]. They are widely claimed to be instrumental in the conservation of tropical forests and wildlife [5] This emphasizes the importance of understanding and monitoring how they react and potentially adapt to different habitat changes. While humans have been present in primate habitats since the millennia, the current rate of forest destruction and fragmentation, is resulting today in prevalent human–wildlife conflicts along protected area boundaries [6]. This situation is deteriorating further given average human population growth rates, reaching nearly double the average of rural growth at the border of some protected areas [7]. The incursions in human cultivations by forest mammals, such as elephants and primates, are one of the most common behavioural responses to both habitat loss and access to new energy-rich food resources (Africa: [8,9]; Asia: [10,11])

Methods

Results

Discussion

Conclusion