體型大小對打鬥行為的影響

The effects of body size on the contest behaviors of Rivulus marmoratus

黃智男(Chih-Nan Huang)

指導教授 ： 許鈺鸚

國立臺灣師範大學/理學院/生命科學研究所/碩士(2005年)

摘要

自從博弈理論被應用於動物間的打鬥行為後，已有越來越多理論生物學家藉由行為的成本與效益的觀點來預測個體在一場競賽中可能採取的打鬥行為，進而發展出許多不同的打鬥模式。依據個體是否會評估對手打鬥能力的假設條件，這些打鬥模式大致可以區分為兩大類：一類認為個體會先評估對手的打鬥能力，再採取相對應行為的「評估模式」；另一類則認為個體不會評估對手的打鬥能力，只依照自己打鬥能力高低來採取相對應行為的「不評估模式」。評估模式預測兩個競爭者打鬥時間的長短與此二競爭者的打鬥能力差異成反比，相對的不評估模式則預測打鬥時間與較弱一方的打鬥能力成正比。Taylor與Elwood在2003年發表一篇重要的研究，其中指出先前的許多研究資料支持個體會評估對手打鬥能力的「評估模式」，可能是因為這些研究資料中的個體間打鬥能力差異與打鬥能力較弱之個體的打鬥能力之間存在著顯著的負相關所造成，而其實這些研究中的個體根本就不會評估對手的打鬥能力，它們應為只依據本身打鬥能力大小而採取相對應行為的「不評估模式」。
　　我們無法直接知道一個個體的打鬥能力高低。而一個個體的體型大小是最常被用來衡量其打鬥能力的型態特徵之一。本研究主要經由控制配對個體的體長，進而檢視以下結果：（１）經由使用體長相近的小競爭個體，檢視大競爭對手的體長對四種打鬥行為（打鬥時間、打鬥強度、威嚇總次數與攻擊總次數）的影響，並以其所得結果來檢驗「評估模式」與「不評估模式」的預測。（２）其他打鬥行為（例如：打鬥輸贏）如何受到競爭者的體長大小影響。除了主要控制競爭者體長大小之外，我在研究中另外控制了可能影響個體打鬥行為的兩個因子：品系與實驗個體的前一次打鬥輸贏結果。
　　在此研究中我總共進行了82場打鬥，其中76場在一小時的觀察時間內有明確的輸贏結果，而其餘有6場在一小時的觀察時間終了時仍未能有明顯結果。以研究結果檢視競爭者的體長對四種打鬥行為的影響，四種中有三種打鬥行為（打鬥時間、打鬥強度與攻擊總次數）受競爭者體長影響的趨勢符合「評估模式」之預測，但是其中只有一個趨勢（打鬥強度）是顯著的。雖然大競爭對手的體長對這些不同打鬥行為的影響變異性很大，但是其主要的趨勢都支持「評估模式」的預測。所以，Rivulus marmoratus的大競爭對手的體長對打鬥行為的影響較符合「評估模式」的預測，而不符合「不評估模式」的預測。
　　除了上述四種打鬥行為外，其他像是打鬥過程（例如誰先起動、誰先發動攻擊等）的其他打鬥行為也受到互相競爭的個體長影響。雖然我於實驗中使用體長大小很相近的小競爭個體，其體長仍然對某些特定打鬥行為（例如：誰先發動攻擊）有顯著的影響。

關鍵字

動物行為 ； 打鬥 ； 體型 ； 體長 ； 評估

並列摘要

Different models of fighting strategy have been developed to predict how individuals should behave in contests based on different assumptions. These fighting models can be divided into two groups, the assessment models and the non-assessment models. In previous studies, supports for the predictions of the assessment models might result from the misleading associations between fighting ability (Resource Holding Potential) disparity and the fighting ability of the weaker opponent as criticized by Taylor & Elwood (2003).
Body size is frequently used as an index for fighting ability. By limiting the variability of the size of the smaller contestants, this study aimed to investigate (1) the effects of the size of the bigger contestants on 4 contest characteristics (contest duration, contest intensity, display frequency and attack frequency in the contests) in order to test predictions from the assessment and the non-assessment models, and (2) whether contest dynamics, contest outcome and other contest behaviors were influenced by the sizes of contestants.
In this study, I staged 82 contests. Seventy six of these contests resulted in obvious dominant/subordinate relationships within 1 hour. However, 6 of them did not resolve in an hour. The effect of size on three out of the 4 contest characteristics were consistent with the predictions from the assessment models (contest duration, contest intensity and attack frequency in the contests); however, only one of these trends was statistically significant (contest intensity). Although the importance of the effects of the size of the bigger contestant on different contest characteristics varied a lot, its significant effect on contest intensity was in support of the assessment models. The results of this study were more consistent with the predictions from the assessment models better than the predictions from the non-assessment models in Rivulus marmoratus.
The contest dynamics and other contest behaviors were also affected by the sizes of the contestants. Although this study attempted to minimize the variability of the size of the smaller contestants, the size of the smaller contestants still had significant influences on some contest behaviors, such as the probability of initiating attacks.

並列關鍵字

animal behavior ； contest behavior ； fighting ； body size ； assessment