Conservation ecology of the golden monkeyscercopithecus mitis kandti and their habitats in Rwanda

Abstract

Habitat loss and fragmentation are major threats to primate populations globally. Many primate species exhibit great flexibility to adapt to habitat change through alterations in multiple aspects of their behavioral ecology. The Endangered golden monkey (Cercopithecus mitis kandti) is an example of this, as it has suffered a series of major habitat loss events across its entire range between 1950s and 1990s. Consequently, golden monkeys only subsist in two forest fragments in the Albertine Rift region, the Virunga massif (Uganda, Rwanda, and Democratic Republic of the Congo) and Gishwati-Mukura National Park (Rwanda) where they mainly inhabit the bamboo zone and tropical montane forest, respectively. Their long-term survival will depend on effective conservation management strategies. However, little is known about the feeding and reproductive behaviors and the conservation status of golden monkeys in their distinct habitats. This doctorial work aimed to provide more information on the abovementioned knowledge gaps. I used scan and ad libitum sampling to record data on feeding and ranging behavior, as well as on demography and reproductive behavior (births and mating events) of two golden monkey groups (groups K~150 individuals and M~60 individuals) in Volcanoes National Park (VNP) and one group (group G~30 individuals) in Gishwati forest for 24 months from January 2017 and 2018. I also examined the phenology of key foods (bamboo shoot in VNP, and fruit trees in the Gishwati forest). Surveys of golden monkeys and illegal human activities in the two fragments were conducted. I used a 13-year data set from group K (2004-2016) and an 8-year data set for group M (2004-2012) acquired from the Dian Fossey Gorilla Fund for assessing birth seasonality in golden monkeys. I also assessed the contribution of forest landscape restoration to primate conservation in the Gishwati-Mukura landscape. All data contributed to the development of the first golden monkey conservation action plan. Results revealed that golden monkeys fed on more than 110 plant species. The VNP groups were mostly folivorous (between 72.8% and 87.16% of the diet) and fed mostly on young bamboo leaves and bamboo shoots, while 48.69% of the diet of the Gishwati group consisted of fruit from 22 different tree and shrub species. Bamboo shoots and fruit are seasonally available foods. Like other blue monkey subspecies, golden monkeys appear to have a flexible dietary strategy and adjust their diet and monthly average home range size to local habitats and available food resources. Food availability strongly determines golden monkey birthing seasons, even at a small spatial scale. The golden monkey reproduction pattern was linked to differences in the timing of bamboo shoot availability and consumption in the Virunga groups, and to fruit availability and consumption in the Gishwati group. Births occurred prior or during vii the peak of key food availability and consumption periods. Interestingly, the two VNP groups had different birthing seasons despite both groups ranging only a short distance (16 km) apart. Females from group K gave birth from September to December, while females from group M gave birth from February to April, which could be explained by spatiotemporal variation in bamboo shoot availability in VNP mainly determined by elevation. Surveys showed that the golden monkeys in VNP almost exclusively range in the bamboo zone, while in Gishwati-Mukura National Park, they mainly occur in the remnant tropical montane forest patch (Gishwati forest) within this park. The 2017-2018 survey estimated 5.47 (95% CI: 3.68-8.14) groups per km2 in VNP, which corresponds to an estimated population size of 4,626 (95% CI: 4,165-5,088) individuals. In the Gishwati forest, group density was much lower and averaged 1.98 (95% CI: 1.27-3.16) per km2, corresponding to 172 (95% CI: 154-190) individuals in 2017-2018. Limited habitat, along with illegal human activities such as bamboo and firewood harvesting, the presence of feral dogs, and cattle grazing, threaten golden monkeys in Rwanda and require continued monitoring and increased protection measures. The forest landscape restoration project which aimed to restore Gishwati provided additional habitat for primates, and the restoration efforts in this forest appear to have reduced conflicts between local communities and primates around the protected area. The golden monkey population in VNP is stable, but its habitat is under high pressure from the poor and dense human population living adjacent to the park, and long-term bamboo phenology data indicate a reduction in the regeneration of bamboo, their key habitat and food. Current changes in key food regeneration, potentially driven by climate change, need to be closely monitored to inform golden monkey conservation management. Despite continued protection efforts, including the recent creation of the Gishwati-Mukura National Park, illegal human activities persist throughout the distribution range of golden monkeys in Rwanda. Habitat loss and degradation, human-wildlife conflict, and limited ecological information are major threats to the golden monkey survival. We developed a five-year conservation action plan (2022-2027) aiming to have viable golden monkey populations thriving across their range by 2027 with targeted actions including reducing anthropogenic threats to the species. This will depend on community engagement and development, community sensitization, tourism, and research, as well as improving protection and law enforcement.