Figure 4.
Survival curve of experiment state in each substrate. (a–c) Points correspond to the experimental values and dashed lines to their nonlinear fitting of the survival curve. (a) Survival curve of still digging experiments (in state 1, 2 or 3). The equation (3.4) fits well the experimental survival in both substrates (granular: ηS = 0.313, cS = 15.46 cm2, n = 24, F1,22 = 1057.3, p < 0.001, r2 = 0.980; cohesive: ηS = 0.239, cS = 14.61 cm2, n = 25, F1,23 = 753.62, p < 0.001, r2 = 0.970). (b) Survival curve of still rounded nests (in first stage, state 1). The equation (3.5) fits well the experimental distributions (granular: η2 = 0.237, c2 = 12.74 cm2, n = 24, F1,22 = 1081.5, p < 0.0001, r2 = 0.980; cohesive: η2 = 0.639, c2 = 5.97 cm2, n = 25, F1,23 = 1745, p < 0.0001, r2 = 0.987). (c) Survival curve of experiments still in second stage (state 2). The experimental distributions could not be fitted by equation (3.5). The c3 and η3 parameters have been determined by using Monte–Carlo simulations (electronic supplementary material). Black filled circles, granular; grey filled circles, cohesive.