Demographic shifts in populations of bioindicator species are widely used to gauge the extent of impacts of human disturbances on ecosystems. Yet, the mechanistic drivers of these demographic changes are often poorly understood. The Atlantic ghost crab, Ocypode quadrata is a bioindicator species of human disturbances on sandy shores, and experiences similar demographic changes as other bioindicator species in response to disturbance by reducing their population abundance and individual body sizes. Previous studies have focused on how human disturbances could cause these demographic changes through altering mortality rates or burrowing behavior. Here, we examine the potential for energetic impacts of human disturbance to cause these demographic shifts. Specifically, we investigate whether variation in habitat quality associated with the level of human disturbance results in reduced diet quality and therefore reduced physiological condition and reproductive effort of ghost crabs. We demonstrate an inverse relationship between diet quality and the level of human disturbance, with resulting reductions in the physiological and reproductive condition of ghost crabs with human disturbance. Our study shows that indirect human disturbance can explain existing variation in demographic characteristics of this bioindicator species, and highlights the importance of understanding bioenergetic relationships between species habitat use and human impacts.

生物指示剂物种种群的人口变化被广泛用于评估人为干扰对生态系统的影响程度。然而，人们对这些人口变化的机理驱动因素往往知之甚少。大西洋幽灵蟹Ocypode quadrata是沙质海岸上人为干扰的生物指标物种，通过减少种群数量和个体大小，对干扰做出响应，其人口变化与其他生物指标物种相似。先前的研究集中在人为干扰如何通过改变死亡率或穴居行为而引起这些人口统计学变化。在这里，我们研究了人为干扰引起的能量冲击导致这些人口变化的潜在可能性。具体来说，我们调查与人为干扰水平相关的栖息地质量变化是否会导致饮食质量下降，从而导致鬼蟹的生理状况和生殖力下降。我们证明了饮食质量与人为干扰水平之间存在反比关系，导致人为干扰的幽灵蟹的生理和生殖状况下降。我们的研究表明，间接的人为干扰可以解释该生物指标物种的人口统计特征存在的变化，并强调了了解物种栖息地使用与人类影响之间的生物能关系的重要性。