Putman Breanna J, Clark Rulon W
Department of Biology, San Diego State University, 5500 Campanile Drive, San Diego, CA 92182, USA; Department of Ecology and Evolutionary Biology, University of California, 621 Young Drive South, Los Angeles, CA 90095-1606, USA; Department of Herpetology, The Natural History Museum of Los Angeles County, 9000 Exposition Blvd., Los Angeles, CA 90007, USA.
Department of Biology, San Diego State University, 5500 Campanile Drive, San Diego, CA 92182, USA.
J Therm Biol. 2017 Apr;65:8-15. doi: 10.1016/j.jtherbio.2017.01.012. Epub 2017 Jan 25.
Increasing temperature due to climate change is one of the greatest challenges for wildlife worldwide. Behavioral data on free-ranging individuals is necessary to determine at what temperatures animals modify activity as this would determine their capacity to continue to move, forage, and mate under altered thermal regimes. In particular, high temperatures could limit available surface activity time and time spent on fitness-related activities. Conversely, performance, such as feeding rate, can increase with temperature potentially having positive fitness effects. Here, we examine how the hunting behaviors of free-ranging Northern Pacific Rattlesnakes (Crotalus oreganus) associate with air temperature and body temperature. We continuously recorded snakes in the field using videography, capturing behaviors rarely considered in past studies such as movements in and out of refuge and strikes on prey. We found that as mean daily air temperature increased, hunting activity and the likelihood of hunting at night decreased, while the number of movements and distance moved per day increased. Snakes typically retreated to refuge before body temperatures reached 31°C. Body temperatures of snakes hunting on the surface were lower compared to temperatures of non-hunting snakes in refuge in the morning, while this relationship was inverted in the afternoon. Snake body size influenced the disparity of these temperatures. Finally, strike initiation and success occurred across a wide range of body temperatures, indicating hunting performance may not be strongly constrained by temperature. These results on the temperatures at which free-ranging rattlesnakes exhibit fitness-related behaviors could be valuable for understanding their vulnerabilities to future climates.
气候变化导致的气温上升是全球野生动物面临的最大挑战之一。要确定动物在何种温度下会改变活动，就需要关于自由放养个体的行为数据，因为这将决定它们在变化的热环境下继续移动、觅食和交配的能力。特别是高温可能会限制可用的地表活动时间以及花在与健康相关活动上的时间。相反，诸如摄食率等表现可能会随着温度升高而提高，这可能对健康产生积极影响。在这里，我们研究自由放养的北太平洋响尾蛇（Crotalus oreganus）的捕猎行为如何与气温和体温相关联。我们在野外使用摄像技术持续记录蛇的行为，捕捉过去研究中很少考虑的行为，比如进出避难所的移动以及对猎物的攻击。我们发现，随着日平均气温升高，捕猎活动以及夜间捕猎的可能性降低，而每天的移动次数和移动距离增加。蛇通常在体温达到31°C之前退回到避难所。早上，在地表捕猎的蛇的体温低于在避难所不捕猎的蛇的体温，而在下午这种关系则相反。蛇的体型影响了这些温度的差异。最后，攻击的发起和成功发生在很宽的体温范围内，这表明捕猎表现可能不会受到温度的强烈限制。这些关于自由放养响尾蛇表现出与健康相关行为的温度的结果，对于理解它们在未来气候下的脆弱性可能很有价值。
