Department of Zoology, University of Melbourne, Melbourne, Victoria, Australia.
PLoS One. 2012;7(4):e34069. doi: 10.1371/journal.pone.0034069. Epub 2012 Apr 3.
Humans are increasingly subsidizing and altering natural food webs via changes to nutrient cycling and productivity. Where human trophic subsidies are concentrated and persistent within natural environments, their consumption could have complex consequences for wild animals through altering habitat preferences, phenotypes and fitness attributes that influence population dynamics. Human trophic subsidies conceptually create both costs and benefits for animals that receive increased calorific and altered nutritional inputs. Here, we evaluated the effects of a common terrestrial human trophic subsidies, human food refuse, on population and phenotypic (comprising morphological and physiological health indices) parameters of a large predatory lizard (∼2 m length), the lace monitor (Varanus varius), in southern Australia by comparison with individuals not receiving human trophic subsidies. At human trophic subsidies sites, lizards were significantly more abundant and their sex ratio highly male biased compared to control sites in natural forest. Human trophic subsidies recipient lizards were significantly longer, heavier and in much greater body condition. Blood parasites were significantly lower in human trophic subsidies lizards. Collectively, our results imply that human trophic subsidized sites were especially attractive to adult male lace monitors and had large phenotypic effects. However, we cannot rule out that the male-biased aggregations of large monitors at human trophic subsidized sites could lead to reductions in reproductive fitness, through mate competition and offspring survival, and through greater exposure of eggs and juveniles to predation. These possibilities could have negative population consequences. Aggregations of these large predators may also have flow on effects to surrounding food web dynamics through elevated predation levels. Given that flux of energy and nutrients into food webs is central to the regulation of populations and their communities, we advocate further studies of human trophic subsidies be undertaken to evaluate the potentially large ecological implications of this significant human environmental alteration.
人类通过改变养分循环和生产力，越来越多地补贴和改变自然食物网。在自然环境中，人类营养补贴集中且持续存在的地方，它们的消费可能会通过改变栖息地偏好、表型和影响种群动态的适应能力属性，对野生动物产生复杂的影响。人类营养补贴从概念上为接受增加热量和改变营养输入的动物带来了成本和收益。在这里，我们通过比较未接受人类营养补贴的个体，评估了一种常见的陆地人类营养补贴——人类食物垃圾，对澳大利亚南部一种大型掠食蜥蜴（约 2 米长）——网纹蟒（Varanus varius）的种群和表型（包括形态和生理健康指标）参数的影响。在人类营养补贴点，与自然森林中的对照点相比，蜥蜴的数量明显更多，性别比例严重偏向雄性。接受人类营养补贴的蜥蜴明显更长、更重，身体状况更好。血液寄生虫在接受人类营养补贴的蜥蜴中明显更低。总的来说，我们的结果表明，人类营养补贴点对成年雄性网纹蟒特别有吸引力，并且对表型有很大的影响。然而，我们不能排除在人类营养补贴点，雄性大型网纹蟒的聚集可能会通过配偶竞争和后代存活率降低以及卵和幼体更容易受到捕食而降低繁殖适应性，从而产生负面影响。这些可能性可能会对种群产生负面影响。这些大型捕食者的聚集也可能通过提高捕食水平对周围食物网动态产生连锁反应。鉴于能量和养分流入食物网是调节种群及其群落的核心，我们提倡进一步开展人类营养补贴研究，以评估这种重要的人类环境改变可能带来的巨大生态影响。
