Yellow fever virus outbreak caused declines in survival and modified dispersal of wild golden lion tamarins

Research Highlight: Ponchon, A., Choquet, R., Martins, A., Ruiz-Miranda, C., Albert, C., & Romano, V. (2026). Yellow fever outbreak temporarily changes dispersal patterns in an endangered primate. Journal of Animal Ecology. https://doi.org/10.1111/1365-2656.70250. Infectious diseases can be drivers of wildlife population dynamics, but how they reshape host movement and social organization remains poorly understood. Ponchon et al. (2026) present one of the rare examples where the impact of a disease outbreak on survival can be measured across a population of wild mammals and subsequently linked to behavioural changes of these animals. They use a unique opportunity by tracking the survival and dispersal decisions of golden lion tamarins (Leontopithecus rosalia) during a sylvatic yellow fever outbreak. Using a 13-year capture-recapture dataset, the authors show that the outbreak caused a temporary decline in adult survival and triggered scale-dependent behavioural responses. While local dispersal within forest fragments decreased, the probability of long-distance dispersal across the matrix increased tenfold. At the same time, group sizes declined during the outbreak, while the number of social groups remained stable and increased after the outbreak. These results indicate that recovery did not involve a simple return to pre-outbreak conditions, but rather a reorganization of social structure characterized by smaller and more numerous groups. These findings highlight that, in vector-borne systems, movement may offer only limited protection against infection and demonstrate that disease outbreaks can lead to lasting population-wide changes in group sizes.