入侵與原生淡水龜的數感認知比較

Abstract

烏龜能辨別數量嗎？這個問題不只是認知心理學的範疇，更與行為生態息息相關。例如雄性會選擇加入雌性個體比較多的群體；領域的佔有者也會依據入侵者的數量決定要逃跑還是奮力一搏，這些行為的決策都奠基於動物具有數量感知能力。在魚類、鳥類和哺乳類上都已有大量研究投入，唯獨爬行動物是否能辨別數量，研究仍非常罕見。在第一章我以臺灣原生淡水龜種斑龜為研究對象，共分為兩個實驗：實驗一為一系列比率由低到高的順序進行的五組測驗；實驗二則是包含共三十二種數量組合的混合測驗。訓練斑龜基於「大於」的抽象規則來辨別數量，而非認特定數量或圖形。研究結果顯示，斑龜能夠成功辨別本研究最難的數字組合：九比十，也發現其數感認知表現符合韋伯率，即兩數量間的比率越高則代表辨別難度越難因此表現變差。另外其表現隨著天數而顯著提升，顯示斑龜具有學習能力。第二章我用全球百大入侵種之一的紅耳龜進行與第一章一樣的實驗，發現當面對必須靈活運用抽象概念的測試時，入侵種的數感表現優於原生龜，顯示紅耳龜可能有較佳的行為彈性。本研究中烏龜所展現的優異數感能力接露爬行動物的認知能力很可能是被嚴重低估的，也暗示其生態行為決策機制可能並不簡單，本論文也是首度試圖透過數感能力連結認知能力與入侵生物學的研究。

Quantity discrimination, the ability to discriminate a magnitude of difference or discrete numerical information, plays a key role in animal behavior. While quantitative ability has been well documented in fishes, birds, mammals, and even invertebrates and in previously unstudied invertebrates and amphibians, it is still poorly understood in reptiles and has never been tested in an aquatic turtle despite the fact that evidence is accumulating that reptiles possess cognitive skills and learning ability. In Chapter 1, I addressed this deficiency in reptiles and investigated the quantitative ability of an Asian freshwater turtle, Mauremys sinensis, using red cubes on a white background in a trained quantity discrimination task. While spontaneous quantity discrimination methods are thought to be more ecologically relevant, training animals on a quantity discrimination task allows more comparability across taxa. I discovered that turtles could successfully discriminate quantities up to of 9 versus 10, and their quantitative performance followed Weber’s law. The gradual improvement of their success rate suggested that turtles possess learning ability. In Chapter 2, I conducted the same experimental design on the notorious invasive red-eared slider, Trachemys scripta elegans. My analyses showed that the invasive sliders showed better quantitative performance when switching to the tests which they had to use the abstract concept of “greater-than” and to abandon their previous choice. The sliders also had better quantitative performance in the initial phase when facing complicated testing pairs. These results revealed that the red-eared slider has higher flexibility than the native M. sinensis. My thesis reveals that the intelligence of reptiles has been long-term underestimated, and provides the first insight into the potentiality of quantitative ability to address the link between cognition and invasion biology.