Routine habitat switching alters the likelihood and persistence of infection with a pathogenic parasite

23 Feb 2018

Animals switch habitats on a regular basis, and when habitats vary in suitability 21 for parasitism, routine habitat switching alters the frequency of parasite exposure 22 and may affect post-infection parasite proliferation. However, the effects of 23 routine habitat switching on infection dynamics are not well understood. 24 2. We performed infection experiments, behavioural observations, and field 25 surveillance to evaluate how routine habitat switching by adult alpine newts 26 (Ichthyosaura alpestris) influences infection dynamics of the pathogenic parasite, 27 Batrachochytrium dendrobatidis (Bd). 28 3. We show that when newts are exposed to equal total doses of Bd in aquatic 29 habitats, differences in exposure frequency and post-exposure habitat alter 30 infection trajectories: newts developed more infections that persisted longer when 31 doses were broken into multiple, reduced-intensity exposures. Intensity and 32 persistence of infections was reduced among newts that were switched to 33 terrestrial habitats following exposure. 34 4. When presented with a choice of habitats, newts did not avoid exposure to Bd, 35 but heavily infected newts were more prone to reduce time spent in water. 36 5. Accounting for routine switching between aquatic and terrestrial habitat in the 37 experiments generated distributions of infection loads that were consistent with 38 those in two populations of wild newts. 39 6. Together, these findings emphasize that differential habitat use and behaviours 40 associated with daily movement can be important ecological determinants of 41 infection risk and severity. 42