Non-breeding territoriality and the effect of territory size on aggression in the weakly electric fish, Gymnotus omarorum
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Agonistic behavior involves the displays that arise when conspecifics compete for valuable resources such as territory. After conflict resolution, dominants obtain priority access to the resource while subordinates lose it. We aimed to evaluate how agonistic encounters mediate the acquisition of different sized territories in the weakly electric fish, Gymnotus omarorum, a species that displays a well-documented non-breeding agonistic behavior very unusual among teleosts. When tested in intrasexual and intersexual dyads in small arenas, a sex-independent dominant-subordinate status emerged after highly aggressive contests in which subordinates signaled submission by retreating and emitting submissive electric signals. We staged dyadic agonistic encounters in a large arena, in which the initial interindividual distance resembled the one observed in nature. We observed the emergence of a dominant-subordinate status after longer but milder contests with rare electric signaling of submission. We found the persistence of dominance over time with no outcome reversion. We observed how dominants exclude subordinates from their conquered resource during all the recording time. Although the territorial behavior of Gymnotus has been put forth since pioneer reports, this is the first study to show how agonistic behavior depends on the territory size in this genus. Agonistic encounters of G. omarorum in the small arena resemble the characteristics of violent-like behaviors. The ease of shifting from mild to high levels of aggression due to confinement, together with the use of electrical signaling of submission, makes this species an excellent model to explore new perspectives in territoriality assessment.
KeywordsTerritoriality Agonistic behavior Electric fish Violence
We specially thank Laura Quintana and Lucía Zubizarreta for their generous comments and suggestions to our manuscript. We are very grateful to Adriana Migliaro, Carlos Passos, Laura Quintana, Federico Reyes, and Lucía Zubizarreta for their useful discussions during the BERTA Workshop, Cerro del Toro, Piriápolis, Uruguay.
This work was supported by National Agency for Research and 50 Innovation (ANII), projects FCE 569 and FCE 4272.
Compliance with ethical standards
Electric fish collection for experimental purposes was authorized by DINARA (National Direction of Aquatic Resources) and MGAP (Ministry of Agriculture and Fisheries), resolution No. 065/2004. All experimental procedures complied with ASAP/ABS Guidelines for the Use of Animals in Research and were approved by our institutional ethical committee (Comisión Bioética, Instituto Clemente Estable, MEC, 007/05/2012).
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