Demographic Structure of Black and Gold Howler Monkeys (Alouatta caraya) in Northeastern Argentina: A Post-Disturbance Baseline Across Contrasting Landscapes.

Yellow fever (YF) outbreaks and anthropogenic fires are major sources of mortality in Neotropical primates, yet their legacy effects on population structure and reproductive output remain poorly quantified. We conducted a comparative assessment of black and gold howler monkey population (Alouatta caraya) across three population contexts in northeastern Argentina: (1) Yellow fever-affected, (2) Yellow fever-free populations, (3) a fire-affected population in Iberá wetlands. Group size was similar across sites, with a median of 9 individuals (range: 3-15). Multimale-multifemale groups predominated across all populations (76%-94%), and adult sex ratios were relatively balanced across sites, ranging from 1.4:1 to 1.6:1 adult females per adult males. Reproductive indicators were consistent among populations, averaging 1.4 immatures per adult female, while infant production ranged from 0.2 to 0.5 infants per adult female across sites. We recorded 60 births, primarily concentrated in autumn. YF-affected sites, which maintain low population densities (0.33 ind/ha), included social units as small as three individuals, despite an overall demographic structure comparable to that of unaffected populations. In contrast, the fire-affected site exhibited a higher proportion of subadult males (28%), consistent with a potential crowding effect (2.22 ind/ha) and dispersal limitation in recently burned remnants. Our findings suggest that A. caraya maintains stable social structures and reproductive output despite disturbances, highlighting demographic resilience. However, persistent low densities in YF-affected sites, altered dispersal patterns in burned landscapes, and the potential effects of isolation and habitat degradation underscore the need for long-term monitoring to evaluate population viability under increasing environmental uncertainty and ongoing landscape change.