Temporal pattern of questing tick Ixodes ricinus density at differing elevations in the coastal region of western Norway

Abstract

BackgroundClimate change can affect the activity and distribution of species, including pathogens and parasites. The densities and distribution range of the sheep tick (Ixodes ricinus) and it’s transmitted pathogens appears to be increasing. Thus, a better understanding of questing tick densities in relation to climate and weather conditions is urgently needed. The aim of this study was to test predictions regarding the temporal pattern of questing tick densities at two different elevations in Norway. We predict that questing tick densities will decrease with increasing elevations and increase with increasing temperatures, but predict that humidity levels will rarely affect ticks in this northern, coastal climate with high humidity.MethodsWe described the temporal pattern of questing tick densities at ~100 and ~400 m a.s.l. along twelve transects in the coastal region of Norway. We used the cloth lure method at 14-day intervals during the snow-free season to count ticks in two consecutive years in 20 m2 plots. We linked the temporal pattern of questing tick densities to local measurements of the prevailing weather.ResultsThe questing tick densities were much higher and the season was longer at ~100 compared to at ~400 m a.s.l. There was a prominent spring peak in both years and a smaller autumn peak in one year at ~100 m a.s.l.; but no marked peak at ~400 m a.s.l. Tick densities correlated positively with temperature, from low densities <5°C, then increasing and levelling off >15-17°C. We found no evidence for reduced questing densities during the driest conditions measured.ConclusionsTick questing densities differed even locally linked to elevation (on the same hillside, a few kilometers apart). The tick densities were strongly hampered by low temperatures that limited the duration of the questing seasons, whereas the humidity appeared not to be a limiting factor under the humid conditions at our study site. We expect rising global temperatures to increase tick densities and lead to a transition from a short questing season with low densities in the current cold and sub-optimal tick habitats, to longer questing seasons with overall higher densities and a marked spring peak.

Parasite load and seasonal migration in red deer

“…The median date of the spring migration of red deer is 8 May, and they remain in their summer range for on average 122 days (Bischof et al 2012), which covers the main tick questing season in Norway (Qviller et al 2014). Migratory red deer are hence less available for the tick population during the summer.…”

Attachment site selection of life stages of Ixodes ricinus ticks on a main large host in Europe, the red deer ( Cervus elaphus )

“…(i) We analysed number of ticks using a negative binomial error known to fit such data better than Poisson [11,13,14] with individual "ID"…”

Potential use of edaphic predatory mites for the control of hematophagous mites (Acari)

“…Thus, the role of the latter in controlling the former could not be determined in the present study. The model shows that ticks are more abundant in Tingvoll than in Isfjorden and, corroborating the findings of Qviller et al (2014), the model obtained in the present work also express the higher tick abundance in the low than the high elevations. Additionally, the negative relation of rainfall with I. ricinus density suggests a detrimental direct or indirect impact of rain on this tick species.…”

“…The loggers were placed approximately one meter above ground to avoid extreme local conditions and variation at ground level. Further details about the collecting sites are given in Qviller et al (2014), a sister study conducted to evaluate the population dynamics of…”