Skip the tropics to avoid malaria?Submitted by editor on 22 January 2016.Get the paper!
Animal migrations play a major role in our understanding of how species are distributed across space and time. Many migratory animals travel enormous distances each year, leaving us to wonder why such long migration routes are necessary. One possible explanation is the avoidance of costly parasite infections. Some of the most impressive migrations on Earth are exhibited by wading shorebirds (which we refer to as waders), with some species travelling over 22,000km on annual migrations from arctic breeding grounds to non-breeding grounds in the southern hemisphere. Waders (and many other types of birds) are sometimes infected with avian malaria parasites (Plasmodium and Haemoproteus spp.), providing a good model to test whether different migration strategies can lead to different parasite infection patterns. In this paper, we use recently developed analyses to test if different migration patterns expose migratory waders to different levels of malaria risk across the globe.
Migratory waders may prefer marine habitats and avoid the tropics, by making extra long migrations, to reduce blood parasite load. Ruddy Turnstone photos taken by Erik Kleyheeg
Our key findings show that migratory waders that avoid using tropical non-breeding grounds, often by actually flying further into more southern latitudes, experience a decreased risk of malaria parasite infection. In addition, we provide evidence that waders that only use saltwater coastlines have significantly lower malaria infection rates than species that use both oceanic and freshwater habitats. The infection patterns shown here indicate that malaria parasites could influence migration patterns and habitat use in migratory waders, providing a platform for future studies of animal migration and disease risk.
Nicholas J. Clark on behalf of the authors