Frequency Matters

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Science  26 Nov 2010:
Vol. 330, Issue 6008, pp. 1156
DOI: 10.1126/science.330.6008.1156-a

Aggressive conflict is dangerous. Thus many animals have evolved signals to advertise their ability to defend resources, such as antlers in elk or bird song. For many aquatic species, however, signaling one's prowess is not so straightforward. Murky environments hinder the ability of receivers to discern visual cues, making proactive signaling more difficult. Amazonian knifefish use an electric sense to navigate and forage in muddy tropical waters. Individuals produce distinct electric signals, which have been implicated in courtship and aggressive displays. Through a series of experiments conducted within a natural population of Amazonian knifefish (Sternarchorynchus sp.) in Peru, Fugère et al. demonstrate that larger males produce higher-frequency signals and that fish that emit higher-frequency signals outcompete those with lower frequencies in direct competition. Furthermore, fish only respond aggressively towards an artificial electric signal played at a frequency lower than their own. Thus, the frequency of an animal's electric discharge accurately signals its resource-holding potential, and competitors heed the electrical warning.

Biol. Lett. 10.1098/rsbl.2010.0804 (2010).

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