Sexual selection for extreme physical performance in a polygynous bird is associated with exceptional sex differences in oxygen carrying capacity

We examined the oxygen carrying capacity of pectoral sandpipers, measured as the volume percentage of red blood cells in blood (haematocrit, Hct). We found a remarkable sex difference in Hct levels, with males having much higher values (58.9 ± 3.8 s.d.) than females (49.8 ± 5.3 s.d.). While Hct values of male pectoral sandpipers are notable for being among the highest recorded in birds, the sex difference we report is unprecedented and more than double that of any previously described. We also show that Hct values declined after arrival to the breeding grounds in females, but not in males, suggesting that males maintain an aerobic capacity during the mating period equivalent to that sustained during trans-hemispheric migration. We conclude that sexual selection for extreme physical performance in male pectoral sandpipers has led to exceptional sex differences in oxygen carrying capacity.PMID:37991194 | DOI:10.1098/rsbl.2023.0391

Source: Biology Letters - November 22, 2023 Category: Biology Authors: Peter Santema Luke Eberhart-Hertel Mihai Valcu Bart Kempenaers Source Type: research