Data from: Fatal attraction: vegetation responses to nutrient inputs attract herbivores to infectious anthrax carcass sites

Parasites can shape the foraging behaviour of their hosts through cues indicating risk of infection. When cues for risk co-occur with desired traits such as forage quality, individuals face a trade-off between nutrient acquisition and parasite exposure. We evaluated how this trade-off may influence disease transmission in a 3-year experimental study of anthrax in a guild of mammalian herbivores in Etosha National Park, Namibia. At plains zebra (Equus quagga) carcass sites we assessed (i) carcass nutrient effects on soils and grasses, (ii) concentrations of Bacillus anthracis (BA) on grasses and in soils, and (iii) herbivore grazing behaviour, compared with control sites, using motion-sensing camera traps. We found that carcass-mediated nutrient pulses improved soil and vegetation, and that BA is found on grasses up to 2 years after death. Host foraging responses to carcass sites shifted from avoidance to attraction, and ultimately to no preference, with the strength and duration of these behavioural responses varying among herbivore species. Our results demonstrate that animal carcasses alter the environment and attract grazing hosts to parasite aggregations. This attraction may enhance transmission rates, suggesting that hosts are limited in their ability to trade off nutrient intake with parasite avoidance when relying on indirect cues.寄生虫可通过传递感染风险的信号，调控宿主的觅食行为。当风险信号与优质草料这类宿主所需的性状同时出现时，个体便需要在获取营养与暴露于寄生虫感染风险之间做出权衡。我们在纳米比亚埃托沙国家公园开展了一项为期3年的炭疽病实验研究，针对当地的哺乳动物草食动物类群，旨在探究这种权衡如何影响疾病传播。我们以平原斑马（Equus quagga）的尸体位点为研究对象，相较于对照位点，利用运动感应相机陷阱（motion-sensing camera traps）开展了三项评估：（1）尸体营养物质对土壤与草本植物的影响；（2）草本植物与土壤中的炭疽芽孢杆菌（Bacillus anthracis, BA）浓度；（3）草食动物的采食行为。研究结果显示，尸体介导的营养脉冲可改善土壤与植被状况，且在宿主死亡后长达2年的时间里，草本植物上仍可检测到炭疽芽孢杆菌。宿主对尸体位点的觅食响应从回避转向吸引，最终转为无偏好，且不同草食动物物种的这类行为响应强度与持续时长存在差异。我们的研究结果表明，动物尸体可改变局部环境，并将采食宿主吸引至寄生虫聚集的区域。这种吸引作用可能会提升疾病传播速率，这意味着当宿主依赖间接信号时，其在营养摄入与规避寄生虫感染之间进行权衡的能力存在局限。