過去的打鬥互動如何影響個體後續打鬥策略

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2013

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一場打鬥可被視為打鬥雙方獲得彼此打鬥能力資訊的過程。打鬥中任何階段,較弱個體都可能因獲得足夠資訊確認自身打鬥能力較差而撤退。在打鬥後,獲勝/落敗個體常會於後續打鬥中展現出攻擊性及獲勝機率上升/下降的現象(勝/敗者效應)。而勝/敗者效應被認為是個體因於先前打鬥中獲得自身打鬥能力較好/差的資訊以致在未來較願意/較不願意參與打鬥。然而,目前並不清楚勝/敗者效應是否僅於先前打鬥結束後發生,或者在打鬥結束前,雙方便可以由打鬥互動中獲得部份打鬥能力資訊並用以調整後續打鬥策略。打鬥雙方若可由打鬥互動中獲得部份打鬥能力資訊,較激烈互動應可提供較精確的打鬥能力資訊因而對後續打鬥決策產生較大影響力。本研究使用Kryptolebias marmoratus,一種紅樹林鳉魚,來檢測此假說。本研究將打鬥互動方式以激烈程度由低到高分為下列四級:目標個體可1.單向觀察訓練對手(單面鏡處理);2.隔著透明隔板與訓練對手相互展示(透明隔板處理);3.自由地與訓練對手互動至分出勝負(無隔板處理);4.自由地與訓練對手互動至分出勝負,並且勝者可繼續追趕、攻擊敗者五分鐘(額外互動處理)。本研究並使用兩種訓練對手處理:打鬥能力分別較目標個體好/差之標準勝/敗者;一共八種互動處理(四級激烈程度×兩種訓練對手)。在互動處理後,給予目標個體一個體型相近的控制對手進行打鬥測試。結果顯示,互動處理進行時,處理激烈程度若越高,目標個體或標準敗者在當下展現出認輸撤退行為的比例也會越高。打鬥測試時,目標個體若與標準勝者進行過無隔板或額外互動,其之後與體型相近的控制對手打鬥時獲勝機率會顯著下降,且打鬥之纏鬥機率及打鬥持續時間較經歷過單面鏡處理的組別低/短;目標個體與標準敗者進行過無隔板處理後,打鬥測試時其率先攻擊、獲勝機率顯著上升,且此組別打鬥纏鬥機率也較單面鏡處理後的組別高。這顯示出:1.個體於激烈程度越高的打鬥互動中所能獲得的打鬥能力資訊也越多且對打鬥當下的決策有較顯著的影響、2.紅樹林鳉魚個體唯有於允許肢體互動的打鬥後,其後續的打鬥行為才會有顯著的改變。
A contest can be viewed as a process for two contestants to assess each other’s fighting ability (FA). At any stage of a contest, the weaker opponent may decide that it has gathered enough information through fighting interactions to confirm its inferior FA, and retreat. Comparing to low intensity interactions (ex: aggressive displays), high intensity interactions (ex: physical interactions) demand higher energy/ability and may reveal more FA information. After a contest is resolved, the winner/loser may raise/lower the evaluation of its FA relative to the population, resulting in a higher/lower aggression and winning probability in future (winner /loser effects). It’s not known whether winner/loser effects form only after fights are resolved, although. One might expect that interactions with higher intensity to reveal more FA information and to have larger impact on contestants’ future contest decisions. I tested this hypothesis by allowing focal individuals of a mangrove killifish, Kryptolebias marmoratus, to have one of four different-intensity interactions (I. one way mirror partition, II. clear partition, III. no partition, and IV. no partition plus 5-minute post-retreat interaction) with either a much stronger/weaker trainer (standard winner/ loser respectively). After the interaction treatments, fights were staged between each focal individual and a size-matched opponent to test the effect of different training interactions. The results show that while in the training period, the retreat probabilities of focal individuals/standard losers were higher as the treatment intensity got higher. After interacting with a standard winner, focal individual in one of the more intense treatments (III and IV), (1) were less likely to win than their opponents; and (2) were less likely to escalate contests and retreated sooner than individuals in treatment I. However, after interacting with a standard loser, only individuals in treatment III were (1) significantly more likely to initiate attacks and to win than their opponents; and (2) were also more likely to escalate contests than those in treatment I. Overall, these results indicate that more intense contest interactions tend to reveal more FA information to focal individuals and focal individuals’ contest behaviors could only be significantly changed while they had a opportunity to fight physically in training period.

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動物打鬥, 勝/敗者效應, 紅樹林鳉魚, animal fight, winner/loser effect, Kryptolabias marmoratus

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