Are crop fields pharmacies for megaherbivores? From ecophysiological studies of elephant (<em>Loxodonta cycotis</em>) crop raiders in Gabon

Damage to crops is a major cause of human-elephant conflict (HEC) in elephant range states. Elephant crop raiding drives farmers' resentment against elephants and reduces local community support for wildlife conservation. While elephant crop raiding ecology is well studied, further investigations on HEC mitigation strategies are still needed. Thus, there is a need to focus on less investigated areas, such as the physiological drivers of elephant crop-raiding behavior, using multidisciplinary sciences. Two physiological proxies, gastrointestinal parasite infestations (GPI) and fecal glucocorticoid metabolite (fGCM) concentrations, common in animal ecophysiology, were used to help understand differences or motivations in the preferences of crops by elephant raiders. The results show, for the first time, that forest elephants may increase the frequency of crop raiding according to GPI, indicating a self-medication behavior. Increases in parasitism prevalence (PP) and parasitism intensity (PI) in sampled boluses led to 28% and 0.16% more intakes of all crops, respectively. Parasitism prevalence (PP) increases in elephant boluses also led to 16% and 25% more bananas and papaya intakes, respectively, while PI increases in boluses led to 0.1% more intakes of both bananas and papaya plants. No such predictions were found for other crops (cassava and palm plant), nor for natural food species. Furthermore, fGCM concentrations were not related to elephant crop raiding. Results highlight a trade-off between the benefit of elephants raiding crops and the danger of encountering farmers by adopting nocturnal crop-raiding behaviours.农作物受损是大象分布国人象冲突（human-elephant conflict, HEC）的主要诱因。大象盗食农作物会引发农户对大象的怨恨情绪，削弱当地社区对野生动物保护的支持度。尽管学界已对大象盗食农作物的生态学开展了充分研究，但人象冲突缓解策略的相关调研仍有待深化。因此，有必要借助多学科手段，聚焦此前研究较少的领域——比如大象盗食行为的生理驱动因素。本研究选用动物生态生理学中常见的两项生理指标：胃肠道寄生虫感染（gastrointestinal parasite infestations, GPI）与粪便糖皮质激素代谢物（fecal glucocorticoid metabolite, fGCM）浓度，以解析盗食大象的作物偏好差异及其动机。研究首次发现，森林象的盗食频率可能随胃肠道寄生虫感染水平升高而提升，这一现象提示其存在自我药疗行为。在所采集的粪便团块中，寄生虫感染率（parasitism prevalence, PP）与感染强度（parasitism intensity, PI）的上升，分别使大象对所有作物的总取食量增加了28%与0.16%。粪便团块中寄生虫感染率的上升，还会分别使大象对香蕉与木瓜的取食量增加16%和25%；而粪便团块感染强度的上升，则会使大象对香蕉与木瓜植株的取食量各增加0.1%。在其他作物（木薯与棕榈植株）以及大象的天然食物物种中，未观察到此类关联。此外，粪便糖皮质激素代谢物浓度与大象盗食农作物的行为并无关联。研究结果揭示了大象盗食作物的收益与采取夜间盗食行为时遭遇农户的风险之间的权衡关系。