Repeatable differences in exploratory behaviour predict tick infestation probability in wild great tits

Abstract Ecological factors and individual-specific traits affect parasite
infestation in wild animals. Ixodid ticks are important ectoparasites of
various vertebrate hosts, which include passerine bird species such as the
great tit (Parus major). We studied various key ecological variables
(breeding density, human disturbance) and phenotypic traits (exploratory
behaviour, body condition) proposed to predict tick infestation
probability and burden in great tits. Our study spanned 3 years and 12
nest box plots located in southern Germany. Breeding, adult great tits
were assessed for exploration behaviour, body condition, and tick burden.
Plots were open to human recreation; human disturbance was quantified in
each plot as a recreation pressure index from biweekly nest box
inspections. Infested individuals were repeatable in tick burden across
years. These repeatable among-individual differences in tick burden were
not attributable to exploration behaviour. However, faster explorers did
have a higher infestation probability. Furthermore, body condition was
negatively correlated to tick burden. Recreation pressure was correlated
to increased infestation probability, although this relationship was just
above the threshold of statistical significance. Our study implies that
avian infestation probability and tick burden are each determined by
distinct phenotypic traits and ecological factors. Our findings highlight
the importance of animal behaviour and human disturbance in understanding
variation in tick burden among avian hosts. Significance statement Various
abiotic and biotic factors, including personality type, influence tick
parasitism in birds, but exactly how all these factors interplay remains
unclear. We studied a wild population of great tits over a 3-year period
and assessed birds for their exploration behaviour and tick infestation.
We found that more explorative great tits were more likely to be infested
with ticks. By contrast, faster explorers did not have higher tick
burdens. Tick burden was nevertheless moderately repeatable among
individuals. Our results imply that animal personality influences the
probability of parasite infestation, and that infestation likelihood
versus intensity are determined by distinct mechanisms. Our work
highlights the importance of animal behaviour to understand parasite
infestation in wild populations.

摘要 生态因子与个体特异性性状会影响野生动物的寄生虫侵染状况。硬蜱（Ixodid ticks）是多种脊椎动物宿主的重要体外寄生虫，宿主涵盖大山雀（Parus major）等雀形目鸟类。本研究针对多项被认为可预测大山雀蜱虫侵染概率与负荷量的关键生态变量（繁殖密度、人类干扰）以及表型性状（探索行为、身体状况）展开研究。本次研究周期为3年，实验区域为德国南部的12处巢箱样地。研究人员对繁殖期的成年大山雀的探索行为、身体状况与蜱虫负荷量进行了评估。所有样地均对人类休闲活动开放；研究人员通过每两周一次的巢箱巡查，量化得到各区域的娱乐压力指数以表征人类干扰程度。个体间的蜱虫负荷量在跨年度观测中具有可重复性，而这类个体间的重复性差异并非由探索行为导致。不过，探索速度更快的个体确实具有更高的蜱虫侵染概率。此外，身体状况与蜱虫负荷量呈负相关关系。娱乐压力与侵染概率升高存在相关性，但该关联仅略高于统计学显著性阈值。本研究表明，鸟类的蜱虫侵染概率与负荷量分别由不同的表型性状与生态因子决定。研究结果凸显了动物行为与人类干扰在解析鸟类宿主间蜱虫负荷量差异中的重要性。

意义阐述 包括性格类型在内的各类非生物与生物因子均会影响鸟类的蜱虫寄生情况，但目前这些因子间的具体相互作用机制仍不明确。本研究针对大山雀的野生种群开展了为期3年的跟踪调查，评估了鸟类的探索行为与蜱虫侵染情况。研究发现，探索性更强的大山雀更易被蜱虫侵染。与之相反，探索速度更快的个体并未表现出更高的蜱虫负荷量。不过，个体间的蜱虫负荷量仍具有中等程度的可重复性。本研究结果表明，动物性格会影响寄生虫侵染概率，而侵染可能性与侵染强度由不同的机制决定。本研究凸显了动物行为在解析野生种群寄生虫侵染情况中的重要性。