Alces alces]]> Dermacentor albipictus]]> Observed links between parasites, such as ticks, and climate change have
aroused concern for human health, wildlife population dynamics, and broader
ecosystem effects. The one-host life history of the winter tick (Dermacentor
albipictus) links each annual cohort to environmental conditions during three
specific time periods when they are predictably vulnerable: spring detachment
from hosts, summer larval stage, and fall questing for hosts. We used
mixed-effects generalized linear models to investigate the drivers of tick loads
carried by moose (Alces alces) relative to these time periods and across
750 moose, 10 years, and 16 study areas in the western United States. We tested
for the effects of biotic factors (moose density, shared winter range, vegetation,
migratory behavior) and weather conditions (temperature, snow, humidity) during
each seasonal period when ticks are vulnerable and off-host. We found that
warm climatic regions, warm seasonal periods across multiple partitions of the
annual tick life cycle, and warm years relative to long-term averages each contributed
to increased tick loads. We also found important effects of snow and
other biotic factors such as host density and vegetation. Tick loads in the western
United States were, on average, lower than those where tick-related die-offs
in moose populations have occurred recently, but loads carried by some individuals
may be sufficient to cause mortality. Lastly, we found interannual variation
in tick loads to be most correlated with spring snowpack, suggesting this environmental
component may have the highest potential to induce change in tick
load dynamics in the immediate future of this region.]]> IN COPYRIGHT - NON-COMMERCIAL USE PERMITTED]]> the original work is properly cited.]]>