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Rival assessment among northern elephant seals: evidence of associative learning during male-male contests.

Casey C, Charrier I, Mathevon N, Reichmuth C - R Soc Open Sci (2015)

Bottom Line: We evaluated the acoustic displays of breeding male northern elephant seals (Mirounga angustirostris), and found that social knowledge gained through prior experience with signallers was sufficient to maintain structured dominance relationships.Using sound analysis and playback experiments with both natural and modified signals, we determined that males do not rely on encoded information about size or dominance status, but rather learn to recognize individual acoustic signatures produced by their rivals.Our findings demonstrate that social knowledge of rivals alone can regulate dominance relationships among competing males within large, spatially dynamic social groups, and illustrate the importance of combining descriptive and experimental methods when deciphering the biological relevance of animal signals.

View Article: PubMed Central - PubMed

Affiliation: Department of Ecology and Evolutionary Biology, and , University of California Santa Cruz , Santa Cruz, CA 95060, USA.

ABSTRACT
Specialized signals emitted by competing males often convey honest information about fighting ability. It is generally believed that receivers use these signals to directly assess their opponents. Here, we demonstrate an alternative communication strategy used by males in a breeding system where the costs of conflict are extreme. We evaluated the acoustic displays of breeding male northern elephant seals (Mirounga angustirostris), and found that social knowledge gained through prior experience with signallers was sufficient to maintain structured dominance relationships. Using sound analysis and playback experiments with both natural and modified signals, we determined that males do not rely on encoded information about size or dominance status, but rather learn to recognize individual acoustic signatures produced by their rivals. Further, we show that behavioural responses to competitors' calls are modulated by relative position in the hierarchy: the highest ranking (alpha) males defend their harems from all opponents, whereas mid-ranking (beta) males respond differentially to familiar challengers based on the outcome of previous competitive interactions. Our findings demonstrate that social knowledge of rivals alone can regulate dominance relationships among competing males within large, spatially dynamic social groups, and illustrate the importance of combining descriptive and experimental methods when deciphering the biological relevance of animal signals.

No MeSH data available.


Related in: MedlinePlus

The conditional strategies of beta males. Panels show the behavioural responses exhibited by beta males when challenged with playbacks of lower ranking males (subordinate) or higher ranking males (dominant). The behavioural responses are expressed by composite scores (PC1 scores) that integrate the assessment of several behavioural parameters (see text for details): lower PC scores indicate a stronger aggressive reaction (shorter latencies, calls produced during the playback and an approach to the loudspeaker), while positive scores indicate a retreat. The target males showed strong differential movements towards or away from the speaker when the calls of familiar subordinate or dominant individuals were presented (left panel, Wilcoxon test, n=10, z=2.547, p=0.011). Conversely, the playback of calls from stranger individuals hardly elicited a behavioural reaction (right panel, Wilcoxon test, n=10, z=1.069 p=0.285). The whiskers on the box plots show min-max.
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RSOS150228F6: The conditional strategies of beta males. Panels show the behavioural responses exhibited by beta males when challenged with playbacks of lower ranking males (subordinate) or higher ranking males (dominant). The behavioural responses are expressed by composite scores (PC1 scores) that integrate the assessment of several behavioural parameters (see text for details): lower PC scores indicate a stronger aggressive reaction (shorter latencies, calls produced during the playback and an approach to the loudspeaker), while positive scores indicate a retreat. The target males showed strong differential movements towards or away from the speaker when the calls of familiar subordinate or dominant individuals were presented (left panel, Wilcoxon test, n=10, z=2.547, p=0.011). Conversely, the playback of calls from stranger individuals hardly elicited a behavioural reaction (right panel, Wilcoxon test, n=10, z=1.069 p=0.285). The whiskers on the box plots show min-max.

Mentions: Beta males presented with calls from familiar dominant and subordinate rivals responded aggressively to the calls of their subordinate opponent by approaching the loudspeaker and vocalizing (i.e. negative PC scores), while they quickly moved away without calling (i.e. positive PC scores) upon hearing the calls of their dominant rival (Wilcoxon matched pairs test on PC1 scores, n=10, Z=2.1915, p=0.028; on PC2 scores: n=10, Z=1.68, p=0.09; figure 6; see the electronic supplementary material, video 2). The first two components of the PCA performed on behavioural measurements showed eigenvalues of more than 1, and explained 53% and 28% of the total variance, respectively. Distance moved, latency to vocalize and number of calls were correlated to PC1 (all positively except latency to vocalize), while latency to orient and latency to move were positively correlated to PC2. In a subsequent experiment, the same dominant–subordinate treatments were presented to 10 beta males of similar status from a distant colony. In this case, the focal males were unfamiliar with the callers. We observed no differential response to the calls of high-ranking and low-ranking strangers (Wilcoxon matched pairs test on PC1 scores, n=10, Z=0.652, p=0.515; on PC2 scores: n=10, Z=0.059, p=0.952; figure 6).Figure 6.


Rival assessment among northern elephant seals: evidence of associative learning during male-male contests.

Casey C, Charrier I, Mathevon N, Reichmuth C - R Soc Open Sci (2015)

The conditional strategies of beta males. Panels show the behavioural responses exhibited by beta males when challenged with playbacks of lower ranking males (subordinate) or higher ranking males (dominant). The behavioural responses are expressed by composite scores (PC1 scores) that integrate the assessment of several behavioural parameters (see text for details): lower PC scores indicate a stronger aggressive reaction (shorter latencies, calls produced during the playback and an approach to the loudspeaker), while positive scores indicate a retreat. The target males showed strong differential movements towards or away from the speaker when the calls of familiar subordinate or dominant individuals were presented (left panel, Wilcoxon test, n=10, z=2.547, p=0.011). Conversely, the playback of calls from stranger individuals hardly elicited a behavioural reaction (right panel, Wilcoxon test, n=10, z=1.069 p=0.285). The whiskers on the box plots show min-max.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4555858&req=5

RSOS150228F6: The conditional strategies of beta males. Panels show the behavioural responses exhibited by beta males when challenged with playbacks of lower ranking males (subordinate) or higher ranking males (dominant). The behavioural responses are expressed by composite scores (PC1 scores) that integrate the assessment of several behavioural parameters (see text for details): lower PC scores indicate a stronger aggressive reaction (shorter latencies, calls produced during the playback and an approach to the loudspeaker), while positive scores indicate a retreat. The target males showed strong differential movements towards or away from the speaker when the calls of familiar subordinate or dominant individuals were presented (left panel, Wilcoxon test, n=10, z=2.547, p=0.011). Conversely, the playback of calls from stranger individuals hardly elicited a behavioural reaction (right panel, Wilcoxon test, n=10, z=1.069 p=0.285). The whiskers on the box plots show min-max.
Mentions: Beta males presented with calls from familiar dominant and subordinate rivals responded aggressively to the calls of their subordinate opponent by approaching the loudspeaker and vocalizing (i.e. negative PC scores), while they quickly moved away without calling (i.e. positive PC scores) upon hearing the calls of their dominant rival (Wilcoxon matched pairs test on PC1 scores, n=10, Z=2.1915, p=0.028; on PC2 scores: n=10, Z=1.68, p=0.09; figure 6; see the electronic supplementary material, video 2). The first two components of the PCA performed on behavioural measurements showed eigenvalues of more than 1, and explained 53% and 28% of the total variance, respectively. Distance moved, latency to vocalize and number of calls were correlated to PC1 (all positively except latency to vocalize), while latency to orient and latency to move were positively correlated to PC2. In a subsequent experiment, the same dominant–subordinate treatments were presented to 10 beta males of similar status from a distant colony. In this case, the focal males were unfamiliar with the callers. We observed no differential response to the calls of high-ranking and low-ranking strangers (Wilcoxon matched pairs test on PC1 scores, n=10, Z=0.652, p=0.515; on PC2 scores: n=10, Z=0.059, p=0.952; figure 6).Figure 6.

Bottom Line: We evaluated the acoustic displays of breeding male northern elephant seals (Mirounga angustirostris), and found that social knowledge gained through prior experience with signallers was sufficient to maintain structured dominance relationships.Using sound analysis and playback experiments with both natural and modified signals, we determined that males do not rely on encoded information about size or dominance status, but rather learn to recognize individual acoustic signatures produced by their rivals.Our findings demonstrate that social knowledge of rivals alone can regulate dominance relationships among competing males within large, spatially dynamic social groups, and illustrate the importance of combining descriptive and experimental methods when deciphering the biological relevance of animal signals.

View Article: PubMed Central - PubMed

Affiliation: Department of Ecology and Evolutionary Biology, and , University of California Santa Cruz , Santa Cruz, CA 95060, USA.

ABSTRACT
Specialized signals emitted by competing males often convey honest information about fighting ability. It is generally believed that receivers use these signals to directly assess their opponents. Here, we demonstrate an alternative communication strategy used by males in a breeding system where the costs of conflict are extreme. We evaluated the acoustic displays of breeding male northern elephant seals (Mirounga angustirostris), and found that social knowledge gained through prior experience with signallers was sufficient to maintain structured dominance relationships. Using sound analysis and playback experiments with both natural and modified signals, we determined that males do not rely on encoded information about size or dominance status, but rather learn to recognize individual acoustic signatures produced by their rivals. Further, we show that behavioural responses to competitors' calls are modulated by relative position in the hierarchy: the highest ranking (alpha) males defend their harems from all opponents, whereas mid-ranking (beta) males respond differentially to familiar challengers based on the outcome of previous competitive interactions. Our findings demonstrate that social knowledge of rivals alone can regulate dominance relationships among competing males within large, spatially dynamic social groups, and illustrate the importance of combining descriptive and experimental methods when deciphering the biological relevance of animal signals.

No MeSH data available.


Related in: MedlinePlus