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Effect of control (adult contact calls) versus experimental (exp; pup-begging calls) playbacks on (a) proportion of food brought to speaker, and levels of (b) prolactin, (c) testosterone and (d) cortisol. Graphs show (a) mean±1 s.d. and (b–d) medians±inter-quartile ranges. Circulating levels of prolactin and cortisol were significantly correlated with one another during the experimental session (Spearman rank correlation, Rs=0.833, p=0.005).
