圆鼻巨蜥的空间需求、热需求和能量分配策略

The water monitor lizard (Varanus salvator) is a large-sized lizard. It has a wide range of variation in body size from hatchling to adulthood, and this feature makes the lizard well suited to the studies addressing the role of body size in influencing space requirement, thermoregulatory behavior (and thus, the set-point and precision of thermoregulation), energy allocation strategy as well as reproductive strategy. Varanus salvator is a highly vulnerable species, but its biology and ecology still remain poorly known. In the present study, we address the following questions: (1) Does the lizard differ from other lizard taxa smaller in size in daily energy requirement? (2) How does the lizard allocate the ingested energy among conflicting demands (maintenance, growth and reproduction),and does large body size evolve in the lizard because a relatively greater amount of energy is allocated toward somatic tissue growth? (3) How does the lizard balance the egg size-number trade-off to maximize reproductive benefits in single reproductive episode? (4) What is the space requirement for a given individual, and does space requirement vary among seasons and among individuals of different size (age) or sex? (5) Does the lizard display thermoregulatory behavior different from other lizard taxa smaller in size and, if so, are the set-point and precision of thermoregulation associated with its unique thermoregulatory behavior? This work will combine laboratory and field experiments. Specifically, energy requirement (daily energy demands), energy allocation (among maintenance, growth and reproduction, and between the size and number of eggs) will be determined in the laboratory enclosures, space requirement will be determined in the field via radio telemetry, and thermal requirement and thermoregulatory behavior will be determined in both the field and the laboratory. Such an approach will allow us to gather data necessary for answer the above questions. Data generated from this study are very useful in developing an effective protection measure for V. salvator, and are also useful in guiding artificial domestication.

圆鼻巨蜥是一种珍稀大型蜥蜴，从孵出到成体体型变化幅度很大，是开展空间需求、热生物学特性和摄入能量分配策略与体型大小之间关系理论研究的理想材料。就保护基础应用研究的迫切性而言，须获得如下信息：（1）圆鼻巨蜥日能量需求量究竟有多大；（2）摄入的能量如何在维持、生长和繁殖等三个彼此互为冲突的能量需求方向之间进行分配，是否把更多的能量用于生长，使之具有较大体型；（3）在单次繁殖事件中用于繁殖的能量投入在后代大小和数量之间的分配；（4）在适合巨蜥生存的有限区域范围内可以释放多少罚没个体；（5）其体温调节是否有区别于小型蜥蜴的显著特点。申请人通过野外遥测、行为观察、繁殖和幼体饲养、食物同化和代谢率测定等实验，检测圆鼻巨蜥的空间需求、热需求和能量分配策略，全面获取保护圆鼻巨蜥所必须的上述信息。围绕大型蜥蜴的空间需求、热需求和能量分配特点为重心收集的数据可为其野外保护和人工驯养提供理论支持和技术指导。

对圆鼻巨蜥体形和雌性繁殖的研究发现：雌性成体的平均体长大于雄性成体，去除体长因素雄性个体有相对较大的头宽，最小繁殖个体体长为565 mm，母体平均单窝产17.1（10-23）枚卵，繁殖期从6月中旬到9月中旬。窝卵数和窝卵重均与母体体长呈正相关；而卵重与母体体长间不存在显著的线性关系。相对较大的母体通常产更多的卵而具有更大的窝卵重。相对窝卵重和母体体长间未发现显著的线性关系。巨蜥科窝卵数和母体平均体长正相关。巨蜥科蜥蜴中，较大的个体产更多更大的卵，从而具有更大的繁殖输出。圆鼻巨蜥成体体温昼夜的平均变化范围为29.7-32.2 C。圆鼻巨蜥成体的选择体温平均为31.2 C，选择体温最低为30.5C最高至31.9 C。圆鼻巨蜥温度生态位位点（Bio1平均值）为26.3 C，降水生态位位点（Bio12平均值）为2182.2 mm/year，温度生态位宽度为30.8 C，降水生态位宽度为2601mm/quarter（采用max Bio16 – minBio17）。与同科其他巨蜥数据比较我们发现：巨蜥科中温度生态位宽度和温度生态位位点两变量存在显著负相关，即地处严寒的物种（即较低的年平均温度Bio1）具有较宽的生态位宽度。降水生态位宽度和降水生态位位点两变量不存在显著相关性。温度生态位宽度和降水生态位宽度两变量之间存在显著正相关，不存在权衡关系。在三个恒定温度（26、28和30 C）孵化圆鼻巨蜥卵，26、28和30 C平均孵化期分别为317.3 d、245.8 d和212.8 天。结合胚胎发育速率、幼体畸形率、幼体表型和幼体生长速率等数据可得出结论：26 C不适合圆鼻巨蜥卵的胚胎发育，而28-30 C位于圆鼻巨蜥卵最佳孵化温度范围之内。测定了圆鼻巨蜥的消化效率和不同年龄阶段（幼体，亚成体和成体）的静止代谢率。新生幼体、亚成体和成体的静止代谢率分别为2.96 mL O2/h（平均体重42.7 g）、9.75 mL O2/h（平均体重149.6 g）和277.04 mL O2/h（平均体重6358.5 g）。圆鼻巨蜥静止代谢率和其体重呈正相关；体重为协变量的单因素协方差分析表明年龄不影响圆鼻巨蜥的静止代谢率。单位体重的静止代谢率与其体重呈负相关。较大的个体具有较高的总代谢率和更低的单位体重代谢率。这些数据可为圆鼻巨蜥的野外保护和人工驯养提供理论支持和技术指导。