O. montana blocks earlier and survives longer after becoming blocked than X. cheopis.

Histograms of the temporal incidence of complete blockage in O. montana and X. cheopis (A, B) and their life span after becoming blocked (C). Dashed lines indicate the mean; curve fitting used a Gaussian model of the frequency distribution data. Blocked O. montana survived significantly longer than blocked X. cheopis; P < 0.0001 by log-rank (Mantel-Cox) test.