EAPSI: Bright coloration and the startle response: an experimental test of a possible anti-predator mechanism

由于栖息地破坏、捕捞和生命早期的高死亡率，世界各地的淡水海龟物种正在减少。许多物种的幼体都有颜色鲜艳的胎盘(腹壳)，随着发育过程而褪色，但人们对这种颜色的作用知之甚少。由于刚孵化的幼鸟在巢中越冬或从巢中出来时会经历高捕食率，因此幼崽胎盘的鲜艳颜色可能具有反捕食功能，以增加生命第一年的存活可能性。这个项目将通过1)使用视觉模型来确定彩绘的海龟和小菜龟在常见捕食者眼中相对于底物的显着性，以及2)量化捕食者对不同颜色的海龟幼体复制品的惊吓反应和重新参与的时间，以研究海龟幼体的胎盘着色的作用，以估计从捕食者手中逃脱的可能性。这项工作将与澳大利亚墨尔本大学的视觉建模和信号着色专家Devi Stuart-Fox博士合作完成。视觉建模和行为实验的结合将为海龟的视觉信号提供新的信息，并可能有助于淡水海龟的保护。将从刚孵化的美洲斑潜蝇和陆龟幼体以及巢附近的未受干扰的地面上获得鸟巢地点的辐照度和反射率测量，以获得背景反射率测量。这些测量允许用包括捕食者光谱敏感度的视觉模型来计算彩色和非彩色对比，以确定显眼程度。通过翻转每个个体的甲壳(背壳)并测量它平均需要多长时间来测量孵化的幼崽的翻正反应。通过比较个体幼崽的翻正时间和幼崽相对于其背景的显眼程度，以及每个捕食者的惊吓反应和重新接触的时间，这个项目将确定明亮的胎盘颜色是否具有反捕食功能。该NSF EAPSI奖是与澳大利亚科学院合作资助的。

Freshwater turtle species worldwide are declining due to habitat destruction, harvesting, and high mortality early in life. Hatchlings of many species have brightly colored plastrons (ventral shell) that fade over the course of development, but very little is known about the function of this coloration. Because hatchlings experience high predation rates while overwintering in or emerging from the nest, the bright coloration of hatchling plastrons may have an anti-predatory function to increase the likelihood of survival during the first year of life. This project will investigate the function of turtle hatchling plastron coloration by 1) using visual modeling to determine the conspicuousness of painted turtle (Chrysemys picta) and diamondback terrapin (Malaclemys terrapin) plastrons against substrates as viewed by common predators and 2) quantifying the startle response and re-engagement time of predators to differently colored replicas of turtle hatchlings to estimate the likelihood of escape from a predator. This work will be done in collaboration with Dr. Devi Stuart-Fox at University of Melbourne in Australia, an expert in visual modeling and signal coloration. The combination of visual modeling and behavioral experimentation will provide novel information on visual signaling in turtles in general, and may contribute to the conservation of freshwater turtles. Irradiance at the nest site and reflectance measurements will be obtained from hatchling C.picta and M.terrapin plastrons and from undisturbed ground near the nest to obtain background reflectance measurements. These measurements allow chromatic and achromatic contrasts to be calculated with visual models that include spectral sensitivities of predators to determine conspicuousness. Hatchling righting responses will be measured by flipping each individual on its carapace (dorsal shell) and measuring the average time it takes to right itself. By comparing the individual hatchling righting time to the conspicuousness of the hatchling against its background and the startle response and re-engagement time of each predator, this project will determine if bright plastron coloration has an anti-predatory function. This NSF EAPSI award is funded in collaboration with the Australian Academy of Science.