眼紋的禦敵功能到底是什麼?

Vallin A, Dimitrova M, Kodandaramaiah U, Merilaita S. (2011) Deflective effect and the effect of prey detectability on anti-predator function of eyespots. Behav Ecol Sociobiol. 65:1629–1636. DOI 10.1007/s00265-011-1173-7[full text]

同心圓的眼紋一般被學者認為是具有禦敵的功能，並於早期實驗得知其具有威嚇天敵的作用，但近期研究發現，眼紋威嚇天敵的作用並非來自於形狀與眼睛相似，而是對比、顯眼性等因素，但眼紋於自然界中仍為十分常見的存在方式，因此作者試圖了解眼紋存在的理由。作者以藍山雀(Cyanistes caeruleus)作為捕食者，以三角型的紙片製成人工獵物(b × h: 30×15 mm2)，再控制獵物的眼紋的大小、數量(0、1、2)和背景差異(以27×21 cm紙板改變獵物背景色)，總共分成兩個實驗，去看不同獵物對捕食者反應的影響。結果顯示：(a) 小眼紋比大眼紋易受到攻擊 (b)獵物和背景的突出程度會比眼紋大小更具影響力 (c) 捕食者的迴避行為在成對眼紋時會比無眼紋好 (d) 威嚇作用只出現在隱避性背景的部分 (e) 眼紋大小和單一大眼紋及無眼紋間無顯著差異。所以總結實驗結果，作者認為影響眼紋功能的主要因子是眼紋和背景的差異度，但天敵的攻擊行為會偏好小型眼紋，表示對天敵為小型的雀形目物種的獵物而言，天敵會攻擊眼紋而避免攻擊獵物本身的重要部位。

眼紋真的可以嚇到天敵嗎？

Vallin A, Jakobsson S & Wiklund C.(2010) Constant eyespot display as a primary defense - survival of male and female emperor moths when attacked by blue tits. 43:9-17.

蝴蝶和蛾類在翅膀上常有大型且突出的眼紋(eyespots)，可以用來防止捕食者的攻擊，早期的研究主要著重在鱗翅目眼紋的突然暴露如何干擾捕食者的議題，在此則以探討鱗翅目眼紋長期暴露的潛在效益。作者以兩種本身有共域狀態的物種：天蠶蛾(Saturnia pavonia)作為獵物，藍山雀(Cyanistes caeruleus)作為捕食者於Tovetorp Zoological Research Station進行實驗，並計錄放置獵物後30分鐘內捕食者的行為，發現為有眼紋的蛾類比無眼紋者容易受到攻擊，而認為鳥並未受到眼紋的驚嚇，但也發現體型較大的雌性蛾類個體和體型較小的雌性個體相比是不容易受到攻擊的，所以獵物可能是以體型大小來驚嚇捕食者，因此作者認為天蠶蛾長時間暴露眼紋的行為會對捕食者造成吸引而非驚嚇。

[Article]The role of eyespots as anti-predator mechanisms, principally demonstrated in the Lepidoptera

Review Article The role of eyespots as anti-predator mechanisms, principally demonstrated in the Lepidoptera
Martin Stevens a1 a1 Ecology of Vision, School of Biological Sciences, University of Bristol, Woodland Road, Bristol, BS8 1UG. UK (E-mail: Martin.Stevens@bristol.ac.uk)

Abstract

Eyespots are found in a variety of animals, in particular lepidopterans. The role of eyespots as antipredator mechanisms has been discussed since the 19th Century, with two main hypotheses invoked to explain their occurrence. The first is that large, centrally located eyespots intimidate predators by resembling the eyes of the predators' own enemies; the second, though not necessarily conflicting, hypothesis is that small, peripherally located eyespots function as markers to deflect the attacks of predators to non-vital regions of the body. A third possibility is also proposed; that eyespots intimidate predators merely because they are novel or rarely encountered salient features. These hypotheses are reviewed, with special reference given to avian predators, since these are likely to be the principal visually hunting predators of the lepidopterans considered. Also highlighted is the necessity to consider the potential influence of sexual selection on lepidopteran wing patterns, and the genetics and development of eyespot formation.

Key Words: eyespots; receiver psychology; antipredator signals; Lepidoptera; deflection; startle displays; false-head; visual signals; colour patterns.