Climate-driven Moose dispersal mediates intestinal parasite infection risk and physiological stress responses

Abstract Climate warming accelerates parasite proliferation and adaptive evolution and increases wildlife vulnerability to migration pressures, habitat loss, and local extinction. Understanding ecological adaptation mechanisms within the climate–wildlife–parasite dynamic has become a critical research focus in conservation biology. For heat-sensitive species like Moose (Alces alces), climate warming is driving a northward range shift. Dispersal facilitates gene flow within and between Moose populations, promoting the sharing of intestinal parasite communities. Intestinal parasites, in particular, pose a significant threat—however, the role of host gene flow in shaping Moose–parasite coexistence under climate warming remains poorly understood. This study used the Moose–intestinal parasite system to examine how heterogeneities to parasite infection and host physiological stress are generated, specifically the contributions of degree of gene flow. We systematically sampled 96 transects of 5 km length covering 6 study sites in the Greater and Lesser Khingan mountains, northeast China, collecting 198 fecal samples for parasite egg/oocyst analysis and fecal cortisol measurements. Results showed that Moose populations with high gene flow (connected populations) exhibit significantly elevated parasite infection risks and fecal cortisol levels compared to isolated populations. This result suggests that dispersal behavior in connected populations increases exposure to parasitic infections, consequently inducing stronger physiological stress responses. Notably, host dispersal patterns fundamentally modulate the complex interactions among parasites, host nutritional status, gut microbiota, and environmental factors. Although connected populations face greater parasitological and physiological challenges during dispersal, they maintain higher population stability than isolated counterparts. These findings highlight the complex interplay between parasites, hosts, and the environment, emphasizing the importance of integrating dispersal studies into conservation planning. Such efforts can provide new insights into host–parasite dynamics, enabling targeted strategies to reduce parasite transmission and enhance Moose resilience in rapidly changing ecosystems.