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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

(a) Locations of the primary (Año Nuevo) and remote (San Simeon) study sites. (b) Example of male–male physical conflict following exchange of displays. (c) The social network of northern elephant seal males as it appeared at the Año Nuevo study site during the 2010–2011 reproductive season. Red dots=‘alpha’ males that controlled female harems over the season; blue dots=‘beta’ males that reliably held harem flanking positions with opportunistic access to females; green dots=‘peripheral’ males that typically lacked access to harems (the ‘peripheral’ males shown on the upper layer of the network were never observed interacting with alphas). Each arrow represents a directed interaction, drawn from a winner to a loser. The thickness of the arrows is proportional to the number of observed competitive events between two males (mean±s.d.=1.95±2.02 events; range 1–19; 1170 competitive events; see Methods for details on data collection). Each alpha male interacted with 37.6±3.7 individuals (range 33–43). The number of interactants for beta males was 26.1±10.5 (range 10–39). More than 97% of relationships between males were fully asymmetric (i.e. the interactions within a given dyad of males were always won by the same individual). The dyad is thus characterized by a well-established ‘dominant–subordinate’ relationship, illustrating the stability of the hierarchy between males along the reproductive season. (d) Aerial schematic of a harem. Red, blue, and green dots represent ‘alpha’, ‘beta’ and ‘peripheral’ males respectively; pink dots represent females.
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RSOS150228F1: (a) Locations of the primary (Año Nuevo) and remote (San Simeon) study sites. (b) Example of male–male physical conflict following exchange of displays. (c) The social network of northern elephant seal males as it appeared at the Año Nuevo study site during the 2010–2011 reproductive season. Red dots=‘alpha’ males that controlled female harems over the season; blue dots=‘beta’ males that reliably held harem flanking positions with opportunistic access to females; green dots=‘peripheral’ males that typically lacked access to harems (the ‘peripheral’ males shown on the upper layer of the network were never observed interacting with alphas). Each arrow represents a directed interaction, drawn from a winner to a loser. The thickness of the arrows is proportional to the number of observed competitive events between two males (mean±s.d.=1.95±2.02 events; range 1–19; 1170 competitive events; see Methods for details on data collection). Each alpha male interacted with 37.6±3.7 individuals (range 33–43). The number of interactants for beta males was 26.1±10.5 (range 10–39). More than 97% of relationships between males were fully asymmetric (i.e. the interactions within a given dyad of males were always won by the same individual). The dyad is thus characterized by a well-established ‘dominant–subordinate’ relationship, illustrating the stability of the hierarchy between males along the reproductive season. (d) Aerial schematic of a harem. Red, blue, and green dots represent ‘alpha’, ‘beta’ and ‘peripheral’ males respectively; pink dots represent females.

Mentions: We worked at Año Nuevo State Park (37.1086 N, −122.338 W) from December through to February for four consecutive years from 2009 to 2013, and 300 km south at San Simeon State Park (35.6512 N, −121.2196 W) during the 2011–2012 breeding season (figure 1a). At Año Nuevo, we dye-marked 30–51 adult males (aged 8–14 years) annually upon their first sighting in our study area—a 1 km long section of sandy beach used by approximately 300 adult females. A subset of adult males also had flipper tags for inter-annual identification. We took calibrated photographs of the males and recorded their location each observation day to determine proximity to female harems as well as to assess site fidelity, movement patterns and rival familiarity. Fewer than 20 adult males were reliably re-sighted at the Año Nuevo study area during each breeding season. At the San Simeon site, we marked and photographed 15 adult males.Figure 1.


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)

(a) Locations of the primary (Año Nuevo) and remote (San Simeon) study sites. (b) Example of male–male physical conflict following exchange of displays. (c) The social network of northern elephant seal males as it appeared at the Año Nuevo study site during the 2010–2011 reproductive season. Red dots=‘alpha’ males that controlled female harems over the season; blue dots=‘beta’ males that reliably held harem flanking positions with opportunistic access to females; green dots=‘peripheral’ males that typically lacked access to harems (the ‘peripheral’ males shown on the upper layer of the network were never observed interacting with alphas). Each arrow represents a directed interaction, drawn from a winner to a loser. The thickness of the arrows is proportional to the number of observed competitive events between two males (mean±s.d.=1.95±2.02 events; range 1–19; 1170 competitive events; see Methods for details on data collection). Each alpha male interacted with 37.6±3.7 individuals (range 33–43). The number of interactants for beta males was 26.1±10.5 (range 10–39). More than 97% of relationships between males were fully asymmetric (i.e. the interactions within a given dyad of males were always won by the same individual). The dyad is thus characterized by a well-established ‘dominant–subordinate’ relationship, illustrating the stability of the hierarchy between males along the reproductive season. (d) Aerial schematic of a harem. Red, blue, and green dots represent ‘alpha’, ‘beta’ and ‘peripheral’ males respectively; pink dots represent females.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4555858&req=5

RSOS150228F1: (a) Locations of the primary (Año Nuevo) and remote (San Simeon) study sites. (b) Example of male–male physical conflict following exchange of displays. (c) The social network of northern elephant seal males as it appeared at the Año Nuevo study site during the 2010–2011 reproductive season. Red dots=‘alpha’ males that controlled female harems over the season; blue dots=‘beta’ males that reliably held harem flanking positions with opportunistic access to females; green dots=‘peripheral’ males that typically lacked access to harems (the ‘peripheral’ males shown on the upper layer of the network were never observed interacting with alphas). Each arrow represents a directed interaction, drawn from a winner to a loser. The thickness of the arrows is proportional to the number of observed competitive events between two males (mean±s.d.=1.95±2.02 events; range 1–19; 1170 competitive events; see Methods for details on data collection). Each alpha male interacted with 37.6±3.7 individuals (range 33–43). The number of interactants for beta males was 26.1±10.5 (range 10–39). More than 97% of relationships between males were fully asymmetric (i.e. the interactions within a given dyad of males were always won by the same individual). The dyad is thus characterized by a well-established ‘dominant–subordinate’ relationship, illustrating the stability of the hierarchy between males along the reproductive season. (d) Aerial schematic of a harem. Red, blue, and green dots represent ‘alpha’, ‘beta’ and ‘peripheral’ males respectively; pink dots represent females.
Mentions: We worked at Año Nuevo State Park (37.1086 N, −122.338 W) from December through to February for four consecutive years from 2009 to 2013, and 300 km south at San Simeon State Park (35.6512 N, −121.2196 W) during the 2011–2012 breeding season (figure 1a). At Año Nuevo, we dye-marked 30–51 adult males (aged 8–14 years) annually upon their first sighting in our study area—a 1 km long section of sandy beach used by approximately 300 adult females. A subset of adult males also had flipper tags for inter-annual identification. We took calibrated photographs of the males and recorded their location each observation day to determine proximity to female harems as well as to assess site fidelity, movement patterns and rival familiarity. Fewer than 20 adult males were reliably re-sighted at the Año Nuevo study area during each breeding season. At the San Simeon site, we marked and photographed 15 adult males.Figure 1.

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