How do recent contest experience and differences in body size jointly influence contest decisions

• Main Authors: Yu-Ju Chen, 陳昱儒
• Other Authors: Yuying Hsu
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/84462065002809766697

碩士 === 國立臺灣師範大學 === 生命科學研究所 === 101 === Animals’ performance in contest is influenced by differences in the contestants’ intrinsic strengths. For example, individuals with a larger weapon or body size are more likely to win than their opponents. Animals’ aggressiveness and winning probabilities are also known to be increased / decreased by winning / losing a recent contest (winner / loser effect). In practice, many different factors may influence contest behaviors at the same time. I investigated how body-size difference and recent contest experience jointly influence contest decisions. Pairs of Kryptolebias marmoratus were divided into three size-difference treatments (Δ, in mm 0<Δ≤1, 1<Δ≤2, 2<Δ≤3) and four treatments with different combinations of recent contest experience: i. both fish no experience; ii. larger fish no experience / smaller fish winning experience; iii. larger fish losing experience / smaller fish no experience or; iv. larger fish losing experience / smaller fish winning experience), a total of 12 (3×4) treatments. The results showed that: (1) Although contest experience influenced an individual’s probability of winning in less intense (non-escalated) fights, body size had an important influence on the outcome of more intense (escalated) fights, whereas contest experience did not; (2) when both the contestants had no recent contest experience, the larger opponent was more likely to win; (3) when the size difference was small (≤1 mm), individuals with a winning contest experience were significantly more likely to win than opponents with a losing experience; (4) size difference and contest experience jointly influence individuals’ contest decisions, a size advantage 2-3 mm compensates for the disadvantage caused by losing experience in likelihood of winning contests. These results could indicate that contest experience modifies an individual’s willingness to fight but does not change its actual fighting ability. When contests are resolved without escalating into physical fights, individuals with better contest experience persist longer before retreating and have a higher chance of winning. But once contests do escalate into physical fights, actual fighting ability (positively correlated with body size) is more important in determining contest outcome than contest experience. Overall, this study shows that body size and contest experience jointly influence contest outcome, but the two factors come into play in contests of different intensities.