Sexual Competition, Coercive Mating and Mate Assessment ... - CPRG

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972 A. Bisazza, S. Manfredi & A. PilastroTable 2: Standard length (mean ‹ SD), number of male copulatory attempts, and attacksby the female in relation to the female's reproductive condition. For behavioural data, medianand interquartile range are givenExperiment n Female SL (mm)No. ofcopulatoryattemptsNo. ofattackstowardsmaleMale-deprived 10 Male-deprived 44.0 ‹ 5.1 52 (46.5±70.3) 2 (0±3.75)Gravid 44.5 ‹ 4.5 52.5 (47.5±66.5) 4.5 (1.75±6.0)Virgin 10 Virgin 41.7 ‹ 2.8 59 (51±64) 4 (1±15.5)Gravid 40.5 ‹ 7.1 43.5 (35±88.8) 16.5 (2.5±34)Post-partum 6 Post-partum a 49.2 ‹ 7.7 27 (21.5±33.5) 6.5 (0±9.75)Gravid 49.6 ‹ 7.4 56 (43.8±58.5) 1.75 (0.38±6.13)a Average of the ®rst 2 d after parturition. SL, standard length.The proportion of male mating attempts towards gravid females was notlower than that towards virgin and deprived females even when the latter werepooled (z ˆ 0.12, p ˆ0.91, n ˆ 20, Wilcoxon signed-ranks test). Males did notshow any mate preference even if only the ®rst 30 or 10 min of observation wereconsidered (z ˆ 0.36, p ˆ0.52; z ˆ 0.02, p ˆ0.99, respectively, Wilcoxon signedrankstest). When data of virgin and deprived females were pooled, non-gravidfemales were signi®cantly less aggressive than gravid females (z ˆ 1.92, p ˆ0.05, nˆ 20, Wilcoxon signed-ranks test). The proportion of attacks performed by thetwo types of females was not signi®cantly correlated with the proportion of malemating attempts received (r ˆ 0.18, n ˆ 20, ns).Post-partum femalesThe results of this experiment showed that females close to parturition werepreferred over normal gravid females, whereas the latter were preferred to thosefemales that had recently delivered young. Two days after parturition any preferencedisappeared and male mating attempts towards postpartum females becameagain close to 50% (Fig. 5). The frequency of male mating attempts towards postpartumfemales di€ered signi®cantly between days (w 2 ˆ 22.4, df ˆ 8, p
Sexual Selection and Size Dimorphism in the One-Sided Livebearer973Fig. 5: Males choosing between gravid and postpartum females: Proportion of the copulatory attempts(% with SD bars) made by males towards the postpartum female in relation to the gravid female,against the female's reproductive cycle (0 ˆ d of parturition; n ˆ 6). Hatched bars indicate a proportionsigni®cantly di€erent from 50% (p
Page 1 and 2: Ethology 106, 961Ð978 (2000)# 2000
Page 3: Sexual Selection and Size Dimorphis
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Sexual Competition, Coercive Mating and Mate Assessment ... - CPRG

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