(2003) Animal signals. Oxford University Press; Searcy, W.A. & Nowicki, S. (2010). The Evolution of Animal Communication. Princeton University Press; Zahavi, A. & Zahavi, A. (1999). The Handicap Principle. Oxford University Press. * An elite group of killers: Beckerman, S., Erickson, P., Yost, J., Regalado, J., Jaram