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Two male parrotfish charge one another four times in a ritual head-butting bout. The subordinate male retired elsewhere after the fourth contact. Seen here in slow-motion; then in real time.

Credit: PLoS ONE, doi:10.1371/journal.pone.0038120 Roldan C. Muñoz, Brian J. Zgliczynski, Joseph L. Laughlin & Bradford Z. Teer

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