“…However, the interaction does not indicate whether these differences are significant or not, so it is possible that the interaction was a product of our sample size. The sex differences observed in howler monkeys are consistent with previous reports in platyrrhine species, including other howler monkey species, 21,22,67 capuchin monkeys, 16,63,64,68,69 owl monkeys, 23 squirrel monkeys, 24 black‐tufted marmoset, 25,26 spider monkeys, 27 and humans 70 . These sex differences have been associated with the stimulatory effect of testosterone on erythropoiesis, and the inhibitory effect of estrogen 16,37,70,71 but also related to genetic differences, such as the difference between males and females in erythropoietin gene and its receptor 72…”