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

由于栖息地的破坏、捕捞和生命早期的高死亡率，全世界的淡水龟物种正在减少。许多种类的幼体都有色彩鲜艳的腹甲（腹壳），在发育过程中会褪色，但对这种颜色的功能知之甚少。由于幼鸟在巢中越冬或从巢中出现时会经历高捕食率，因此幼鸟胸甲的明亮着色可能具有抗捕食功能，以增加生命第一年的生存可能性。本研究将探讨稚龟胸甲着色之功能，方法为：1）以视觉模拟来判定彩绘龟的显著性（刺龟属）和菱纹龟（Malaclemys terrapin）胸甲对常见捕食者所观察到的底物的反应; 2）量化惊吓反应并重新评估捕食者与不同颜色的海龟幼龟复制品的接触时间，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Devi Stuart-Fox博士合作完成，他是视觉建模和信号着色方面的专家。视觉建模和行为实验的结合将提供新的信息在海龟的视觉信号，并可能有助于淡水龟的保护。将从刚孵化的C.picta和M.terrapin胸甲以及巢附近未受干扰的地面获得巢址的辐照度和反射率测量值，以获得背景反射率测量值。这些测量允许彩色和无色的对比度计算与视觉模型，包括光谱敏感性的捕食者，以确定显着。幼雏的扶正反应将通过翻转每个个体的背甲（背壳）并测量其扶正所需的平均时间来测量。通过比较个体幼体的翻正时间与幼体在其背景下的显著性以及每个捕食者的惊吓反应和重新参与时间，本项目将确定明亮的胸甲着色是否具有抗捕食功能。这个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.