Discrimination of the mate's call was studied in the king penguin Apenodytes patagonicus by considering two single parameters, syllable duration and pitch, both predicted by the acoustic analysis to be potentially involved in the identification process. The within-individual variation for syllable durations (average coefficient of variation: 4.3%) was 2.9 times smaller than the variation between individuals. The recognition was however not significantly altered by an alteration of the syllable duration of 20%. The mean within-individual variation for pitch (averaging coefficient of variation: 1.6%) was 4.3 times smaller than the variation between individuals. An alteration of the pitch as much as 10% was however necessary to hamper the recognition. Role of the two parameters in the discrimination of the mate's call are discussed in view of the knowledge about the auditory duration and pitch discrimination in birds, as well as their potential integration in the decision rules.