Chapman Colin A, Wasserman Michael D, Gillespie Thomas R, Speirs Michaela L, Lawes Michael J, Saj Tania L, Ziegler Toni E
Department of Anthropology and McGill School of Environment, McGill University, Montreal, QC H3A 2T7, Canada.
Am J Phys Anthropol. 2006 Dec;131(4):525-34. doi: 10.1002/ajpa.20477.
Identifying factors that influence animal density is a fundamental goal in ecology that has taken on new importance with the need to develop informed management plans. This is particularly the case for primates as the tropical forest that supports many species is being rapidly converted. We use a system of forest fragments adjacent to Kibale National Park, Uganda, to examine if food availability and parasite infections have synergistic affects on red colobus (Piliocolobus tephrosceles) abundance. Given that the size of primate populations can often respond slowly to environmental changes, we also examined how these factors influenced cortisol levels. To meet these objectives, we monitored gastrointestinal parasites, evaluated fecal cortisol levels, and determined changes in food availability by conducting complete tree inventories in eight fragments in 2000 and 2003. Red colobus populations declined by an average of 21% among the fragments; however, population change ranged from a 25% increase to a 57% decline. The cumulative basal area of food trees declined by an average of 29.5%; however, forest change was highly variable (a 2% gain to a 71% decline). We found that nematode prevalence averaged 58% among fragments (range 29-83%). The change in colobus population size was correlated both with food availability and a number of indices of parasite infections. A path analysis suggests that change in food availability has a strong direct effect on population size, but it also has an indirect effect via parasite infections.
识别影响动物密度的因素是生态学的一个基本目标，随着制定明智管理计划的需求，这一目标变得愈发重要。对于灵长类动物而言尤其如此，因为支撑许多物种生存的热带森林正在迅速转变。我们利用乌干达基巴莱国家公园附近的森林碎片系统，来研究食物可利用性和寄生虫感染对红疣猴（Piliocolobus tephrosceles）数量是否具有协同影响。鉴于灵长类动物种群规模通常对环境变化反应缓慢，我们还研究了这些因素如何影响皮质醇水平。为实现这些目标，我们监测了胃肠道寄生虫，评估了粪便皮质醇水平，并通过在2000年和2003年对八个碎片区域进行完整的树木清查，确定了食物可利用性的变化。各碎片区域的红疣猴数量平均下降了21%；然而，种群变化幅度从增长25%到下降57%不等。食物树的累计断面积平均下降了29.5%；然而，森林变化差异很大（从增加2%到下降71%）。我们发现，各碎片区域中线虫感染率平均为58%（范围在29%-83%之间）。疣猴种群规模的变化与食物可利用性以及一些寄生虫感染指标均相关。路径分析表明，食物可利用性的变化对种群规模有很强的直接影响，但它也通过寄生虫感染产生间接影响。
