Long-term jaguar demography underscores the ecological value of Amazonian floodplains

Assessing population dynamics is key for advising conservation strategies for carnivores, yet long-term demography remains rare. Jaguars (Panthera onca) have lost 52% of their historical distribution, and even in the Amazon, their largest continuous habitat, we lack knowledge on critical vital rates including survival, recruitment, and population trends. Through monitoring spanning 17 years, we provide the longest jaguar study to date and the first open-population assessment in an Amazon flood-pulse ecosystem increasingly exposed to extreme climatic events. We evaluated the effect of flood pulses on jaguar demography in the Amazon using spatially explicit open-population capture–recapture models applied to a dataset from the Mamirauá Sustainable Development Reserve, the first community-based management reserve in Brazil. We also contextualized these estimates with those reported across 10 ecoregions. We found that recruitment was lower for females (0.15) than males (0.26), while apparent survival was constant (0.76). Session-specific densities (3.21–15.15 ind./100 km²) ranked among the highest reported for jaguars across their distribution. However, open-population models indicated that female density decreased by 77% between 2005 and 2022 and the observed population growth rate showed a declining trend (mean = 0.97). Synthesis and applications. Our results provide the first estimates of recruitment and apparent survival for Amazonian jaguars, key parameters for guiding conservation. We show that seasonal wetlands—the Amazonian floodplain forest and reported estimates from Pantanal and the Llanos—harbour the highest jaguar densities across the species' range. However, the high density in Mamirauá may conceal underlying vulnerability. Long-term dynamics indicated a demographic shift: male influx increased, while female numbers declined. We suggest that this pattern reflects reduced reproductive output, potentially driven by increased infanticide following male immigration associated with local male-biased hunting. These findings highlight the need to move beyond abundance-based assessments and incorporate demographic dynamics into conservation planning. Strengthening community-based management, particularly by safeguarding breeding females, is critical to long-term population viability. Amazonian floodplains face increasing threats from extreme climate events, yet are still overlooked in large-scale conservation planning, underscoring the urgency of addressing anthropogenic and climate-driven threats to these high density but vulnerable populations.