Distribution of and in cage protection environments for the conservation of Japanese rock ptarmigans () in the Japanese Alps.

Japanese rock ptarmigans, , are classified as an endangered species in Japan and are found only in the Japanese Alps. The number of birds has decreased in the last half century and cage protection projects have been undertaken as conservation strategies (one of the projects for the recovery plan of Japanese rock ptarmigan) in the mountains. During the period with cage protections, some chicks died and two spp., and , were identified in the chicks. Here, we examined the soil within the cages and in the surrounding environment to assess potential sources of infection between July to August 2020. We found high numbers of oocysts in the cages, especially at the back sides where the ptarmigan family frequently congregated, but soils in other areas outside the cages were less contaminated or not contaminated at all. The time required for more than 50% of the oocysts to sporulate at 15, 20 and 25 °C for was 20, 11, and 5 h, respectively, and 72, 48 and 18 h, respectively, for . Our results cast some doubt that coprophagia by chicks is the source of infection because chicks consumed fresh cecal feces (approximately within 1 h) as far as we know, and instead, the protected chicks might be directly or indirectly infected by oocysts in soils or the environment.