Differences in Flow Regime Influence the Seasonal Migrations, Body Size, and Body Condition of Western Pond Turtles (Actinemys marmorata) that Inhabit Perennial and Intermittent Riverine Sites in Northern California
Differences in Flow Regime Influence the Seasonal Migrations, Body Size, and Body Condition of Western Pond Turtles (Actinemys marmorata) that Inhabit Perennial and Intermittent Riverine Sites in Northern California
复制标题
水流状况的差异影响栖息在北加州常年和间歇性河流地区的西部池塘龟（Actinemys marmorata）的季节性迁徙、体型和身体状况
作者：
Cheryl A. Bondi;Sharyn B. Marks
生活在流水中的物种已经进化出了生命史策略和形态特征，使它们能够在波动的河流环境中生存。河龟的行为反应通常与季节性干旱和洪水有关，形态变化与河流的物理栖息地有关。我们比较了两种不同水流状态下的西塘龟（Actinemys marmorata）的运动行为、体型和身体状况：一种是受水坝影响的调节河段，另一种是大坝上游的自然间歇河段。我们使用无线电遥测技术来追踪这两个地点的海龟的季节性活动，并通过潜水调查收集的数据来比较体型和状况。我们发现迁移的时间受到流动状态的显著影响。断续河段的龟离河早于多年生河段，春季洄游早于多年生河段。总体而言，与多年生河段的海龟相比，间歇河段的海龟每年在水中停留的时间更少，成年海龟明显更小，身体状况也更低。在我们的研究系统中，一座大坝将历史上断续河段的一部分变成了多年生河段；这显然有一些积极的影响，如增加觅食时间，更大的体型，更好的身体状况。然而，饲养幼龟以保证种群的繁殖和持续，可能会在栖息地质量方面进行权衡。
Species inhabiting running waters have evolved life-history strategies and morphological characteristics that allow them to survive in fluctuating river environments. Riverine turtles often have behavioral responses associated with seasonal drying and flooding, and morphological variation that is correlated with physical instream habitat. We compared movement behavior, body size, and body condition of Western Pond Turtles (Actinemys marmorata) under two different flow regimes: a regulated reach with dam-influenced perennial flow and a naturally intermittent reach upstream of the dam. We used radiotelemetry to track the seasonal movements of turtles at both sites and compared body size and condition through data gathered during snorkel surveys. We found that timing of migration was significantly influenced by flow regime. Turtles in the intermittent reach departed the river earlier than those in the perennial reach, and also migrated to the river earlier in the spring. Overall, turtles from the intermittent reach spent less time annually in the water, and adults were significantly smaller and had lower body condition compared to those from the perennial reach. In our study system, a dam converted part of a historically intermittent reach to a perennial one; this apparently had some positive effects, such as increased foraging time, larger body size, and better body condition. However, there may be tradeoffs with regard to habitat quality for rearing juvenile turtles to assure recruitment and persistence of the population.