Institute of Conservation Biology and Environmental Management, School of Biological Sciences, University of Wollongong, Australia.
Comp Biochem Physiol A Mol Integr Physiol. 2012 Feb;161(2):216-29. doi: 10.1016/j.cbpa.2011.10.027. Epub 2011 Nov 3.
Feral goats (Capra hircus) are ubiquitous across much of Australia's arid and semi-arid rangelands, where they compete with domestic stock, contribute to grazing pressure on fragile ecosystems, and have been implicated in the decline of several native marsupial herbivores. Understanding the success of feral goats in Australia may provide insights into management strategies for this and other invasive herbivores. It has been suggested that frugal use of energy and water contributes to the success of feral goats in Australia, but data on the energy and water use of free-ranging animals are lacking. We measured the field metabolic rate and water turnover rate of pregnant and non-pregnant feral goats in an Australian rangeland during late summer (dry season). Field metabolic rate of pregnant goats (601 ± 37 kJ kg(-0.73)d(-1)) was 1.3 times that of non-pregnant goats (456 ± 24 kJ kg(-0.73)d(-1)). The water turnover rate of pregnant goats (228 ± 18 mL kg(-0.79)d(-1)) was also 1.3 times that of non-pregnant goats (173 ± 18 kg(-0.79)d(-1)), but the difference was not significant (P=0.07). There was no significant difference in estimated dry matter digestibility between pregnant and non-pregnant goats (mean ca. 58%), blood or urine osmolality, or urine electrolyte concentrations, indicating they were probably eating similar diets and were able to maintain osmohomeostasis. Overall, the metabolic and hygric physiology of non-pregnant goats conformed statistically to the predictions for non-marine, non-reproductive placental mammals according to both conventional and phylogenetically independent analyses. That was despite the field metabolic rate and estimated dry matter intake of non-pregnant goats being only 60% of the predicted level. We suggest that general allometric analyses predict the range of adaptive possibilities for mammals, but that specific adaptations, as present in goats, result in ecologically significant departures from the average allometric curve. In the case of goats in the arid Australian rangelands, predictions from the allometric regression would overestimate their grazing pressure by about 40% with implications for the predicted impact on their local ecology.
野生山羊（Capra hircus）广泛分布于澳大利亚大部分干旱和半干旱的牧场，它们与家畜竞争，对脆弱的生态系统造成放牧压力，并被牵连到几种本地有袋目草食动物的减少。了解野生山羊在澳大利亚的成功可能为管理这种和其他入侵草食动物提供思路。有人认为，节俭地利用能源和水有助于野生山羊在澳大利亚的成功，但缺乏关于自由放养动物的能量和水利用的数据。我们在澳大利亚牧场的夏末（旱季）测量了怀孕和未怀孕的野生山羊的野外代谢率和水周转率。怀孕山羊的野外代谢率（601 ± 37 kJ kg(-0.73)d(-1)）是未怀孕山羊的 1.3 倍（456 ± 24 kJ kg(-0.73)d(-1)）。怀孕山羊的水周转率（228 ± 18 mL kg(-0.79)d(-1)）也是未怀孕山羊的 1.3 倍（173 ± 18 mL kg(-0.79)d(-1)），但差异不显著（P=0.07）。怀孕和未怀孕山羊的估计干物质消化率无显著差异（平均约为 58%），血液或尿液渗透压或尿液电解质浓度无差异，表明它们可能正在食用相似的饮食，并能够维持渗透平衡。总体而言，未怀孕山羊的代谢和水分生理学在统计学上符合根据传统和系统发育独立分析对非海洋、非生殖胎盘哺乳动物的预测。尽管未怀孕山羊的野外代谢率和估计干物质摄入量仅为预测水平的 60%。我们认为，一般的比例分析预测了哺乳动物适应的可能性范围，但特定的适应，如山羊所具有的，导致了与平均比例曲线的显著偏离。就澳大利亚干旱牧场的山羊而言，比例回归的预测会高估它们的放牧压力约 40%，这对它们对当地生态的预测影响有影响。
