MATRIZ POSITIVISTA
VII. HACIA LA CONSTRUCCIÓN DE NUEVOS HORIZONTES EPISTEMOLÓGICOS
Females showed a mating preference for larger males (Table 2.3.1); they spent a greater amount of total amount of time (Fig. 2.3.1), and a greater mean duration per visit (Fig. 2.3.2) with larger males. When analysing the data using the mean values from the four females assigned to each male pair, females spent a significantly greater total amount of time with larger males (Wilcoxon Signed Ranks, Z = 2.101, p = 0.036, n = 15) and tended to stay longer per visit (greater mean duration) with larger males (Wilcoxon Signed Ranks, Z = 1.931, p = 0.053, n = 15). There was no significant difference in the number of visits, duration proportion or relative proportion of time between different sized males (P = 0.1 to 0.32).
Using linear mixed models, male mass correlated positively with female preference behaviour (Table 2.3.2). Females spent more time overall (Fig. 2.3.3), more time per visit (Fig. 2.3.4), and a greater overall proportion of her time (Fig. 2.3.5) with the larger of the two males. Females also spent a greater relative proportion of time with the larger of the two males. Using female mass and male mass as fixed factors and female identity as a random factor, the total duration (F = 14.216, df = 1,117, p < 0.001), mean duration (F = 6.141, df = 1,117, p = 0.015), duration proportion (F = 8.451, df = 1,117, p = 0.004) and relative proportion (F = 11.879, df = 1,117, p = 0.001) of time was greater with larger males. There was, however, still no significant difference between the number of times a female visited each male’s preference zone.
The level of female preference did not differ significantly across the male pairs (Table 2.3.3). Using linear mixed models with male pairs as the fixed factor and female identity nested within male pair as a random factor, there was no difference in the number of visits (F = 0.599, df = 1,45, p = 0.851), the total duration (F = 0.168, df = 105, p = 1.000) or the mean duration of visits to males (F = 0.892, df = 1,105, p = 0.569) across male pairs.
Mean female mass did not differ significantly across the male pairs (F = 1.655, df = 1,14, p = 0.101), however, females were assigned to pairs that differed significantly in the size of the test males (Table 2.3.4), which raises some concerns about females choice being hindered by extremes in male size forcing a sub-optimal choice. The difference between the mass of the female and the larger male (F = 2.579, df = 1,14, p = 0.008), and also between the mass of the female and the smaller male (F = 3.328, df = 1, 14, p = 0.001) differed significantly among male pairs.
Interestingly, there was some evidence for a female preference being condition-dependent (Fig. 2.3.6). I calculated the spearman rank correlation between female size and the relative proportion of time
spent with the preferred male for all 15 pairs. The mean correlation was significantly greater than zero (mean rs = 0.307, n = 15, p = 0.024; one-sample t-test) showing that larger females exhibited a stronger preference for the preferred male than smaller females. Using the same approach, there was also evidence of size assortative mating (Fig. 2.3.7). Larger females had a tendency to spend relatively more time with larger males compared to the time they spent with smaller males (mean rs = 0.253, n = 15, p = 0.072; one-sample t-test).
Table 2.3.1 Wilcoxon Signed Ranks test comparing the mean values across the four females assigned to each pair for the large and small male (n = 15 male pairs).
Response Variable Mean ± SD Z P-value
Mean of Number of Visits
Large - 9.27 ± 2.95
Sm all-8 .4 3 ±3.23 -0.995 0.320
Mean of Total Duration (sec)*
Large - 556.39 ± 224.27
Sm all-29 6.4 5 ± 194.38 -2.101 0.036
Mean of Mean Duration (sec)*
Large - 144.89 ± 138.10
Small - 54.04 ± 52.43 -1.931 0.053
Mean of Duration Proportion
Large - 0.44 ±0.19
Sm all-0 .2 7 ±0.19 -1.647 0.100
Mean of Relative Proportion
Large-6 1 .1 5 ±23.01
Sm all-3 8 .8 5 ±23.01 -1.647 0.100
Table 2.3.2 Linear mixed models with female mass and male mass as fixed factors and female identity as a random factor). Variables marked * are significant at the 0.05 level.
Response Variable Dependent Variable df F Sig.
Number of Visits Male Size 1,58 0.773 0.206
Female Mass 1,58 1.634 0.386
Total Duration Male Size* 1,117 14.216 0.000*
Female Mass 1,117 2.215 0.148
Mean Duration Male Size* 1,117 6.141 0.015*
Female Mass 1,117 0.089 0.766
Duration Proportion Male Size* 1,117 8.451 0.004*
Female Mass 1,117 2.032 0.157
Relative Proportion Male Size* 1,117 11.879 0.001*
Female Mass 1,117 0.000 1.000
Table 2.3.3 Linear mixed models with male pair as a fixed factor and female identity nested within male pair identity as a random factor.
Response Variable df F Sig.
Number of Visits 14,45 0.599 0.851
Total Duration 14,105 0.168 1.000
Mean Duration 14,105 0.892 0.569
Table 2.3.4 One way ANOVA on female mass, the difference between female mass and the mass of the larger male (Larger Male Difference), and the difference between female mass and the mass of the smaller male (Smaller Male Difference) across pairs.
Response Variable df F Sig.
Female Mass 14, 59 1.655 0.101
Larger Male Difference 14, 59 2.579 0.008 Smaller Male Difference 14, 59 3.328 0.001
3.0 ~ 2.5 - 2.0 ” (J 4> 3 cr 4) S_ fa 1.5 - 1.0 - 0.5 - 00 --- -1000 -800 -600 -400 -200 0 200 400 600
Difference in Mean Total Duration
I
800 11000
Figure 2.3.1 The means of the difference in total duration (average across four females per male)
between the larger and smaller male in a pair (Wilcoxon Signed Ranks, Z = -2.101, p = 0.036; n = 15 male pairs). Positive values indicate that females spent more time with the larger male.
0.5 -
Difference in Mean Duration
Figure 2.3.2 The means of the difference in mean duration (average across four females per male) between the larger and smaller male in a pair (Wilcoxon Signed Ranks, Z = -1.931, p = 0.053; n = 15 male pairs). Positive values indicate that females spent more time with the larger male.
600 -
Large Male
Small Male
Figure 2.3.3 Mean ± SE of the total duration of time females spent with large and small males (F = 14.216, df = 1, 117, p < 0.001).
0.50-
Large mile
Small male
Figure 2.3.4 Mean ± SE for the duration proportion (proportion of total observation time) females spent with large and small males (F = 8.451, df = 117, p = 0.004).
Figure 2.3.5 Mean ± SE for the proportion of time females spent with large and small males relative to the amount of time spent with the other male (F = 11.879, df = 1,117, p = 0.001).
-1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0
S pearm ini’ s correlation
Figure 2.3.6 Histogram of Spearman’s rank correlations between female size and time spent with the preferred male in a pair (n = 4 per correlation) showing that larger females spent relatively more time with preferred males (one-sample t-test, t = 2.52, p = 0.024, n = 15 male pairs).
5- 4“ u 3 3
ss
< u pN 2- 1 - H 1* ' t f « - - 4 . > . ' , ; •. I I I ■1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4Sp eann an*s con- elati on
0.6 0.8 1.0
Figure 2.3.7 Histogram of Spearman’s rank correlations between female size and time spent with the larger male in a pair (n = 4 per correlation) showing that larger females tended to spend more time with larger males (one-sample t-test, t = 1.95, p = 0.072, n = 15 male pairs).