A 25-year longitudinal assessment of Macaca sylvanus population dynamics and forest decline in Morocco's Middle Atlas

Abstract

Primate populations are undergoing rapid declines globally. Long-term data are critical for understanding population dynamics and guiding conservation, yet are rare for many threatened species. We conducted a 25-year longitudinal study (1993–2017) to quantify population trends and the effectiveness of conservation measures of the endangered Barbary macaque (Macaca sylvanus) in the Middle Atlas of Morocco, its largest remaining habitat. The study observed a decline from 25 individuals/km² in 1994 to 5–7 individuals/km² by 2002, driven by habitat degradation, juvenile trafficking, and competition with livestock. From 2005 onwards, conservation measures, including the establishment of Ifrane National Park, anti-poaching campaigns, and reduced grazing pressure, supported a partial recovery, with densities reaching 21 individuals/km² by 2017. Key factors contributing to this recovery include enhanced juvenile survival, by reduced poaching, and immigration of adult and subadult males from degraded regions. Despite these apparently positive trends, the population shows a pronounced male bias and static female numbers, suggesting persistent ecological challenges. This demographic imbalance reflects the Middle Atlas cedar forest's role as a refuge but also highlights its vulnerability as surrounding habitats degrade. The findings underscore M. sylvanus as a biological indicator of forest ecosystem health and reveal that the current recovery is contingent on continued conservation efforts. To ensure long-term sustainability, conservation strategies must prioritize female survival, reproductive success, and broader habitat restoration.

These insights reinforce the importance of long-term monitoring in uncovering the deep interconnections between ecological integrity, human activity, and conservation policy that shape outcomes for endangered species.