Repeatability and consistency of female preference behaviours in a northern swordtail, Xiphophorus nigrensis

Informative and reliable measures of mate choice are essential for accurately identifying female preference patterns across species. Here we identify female receptivity behaviours in mate choice experiments in a species of northern swordtails, Xiphophorus nigrensis, and quantify repeatability and consistency of different female preference indexes (association time and receptivity behaviour). We first identified receptivity behaviour by examining female behaviours towards males in both viewing-only (barrier) and free-ranging (barrier-free) trials. Receptivity behaviours were identified as behaviours that females displayed in the barrier-free environment preceding putative copulation events. Female glide response was significantly correlated with association time in the barrier trials, and was also the most frequently displayed female behaviour in both barrier and barrier-free trials. A second experiment examined the consistency and repeatability of these preference indexes in X. nigrensis females for large versus small males on three different days. Repeatability (intraclass correlation, r) and individual consistency (coefficient of variation) for each preference index (association time and glides) were compared across 15 females. Females showing the strongest preference for males also displayed the greatest consistency in behavioural responses across trials. Repeatability estimates were much higher for association time (r = 0.322) than they were for glides (r = −0.088). Overall, our results indicate that while both glides and association time identify preferences across females, association time represents a more consistent and repeatable estimate of preference.