High rates of pregnancy loss by subordinates leads to high reproductive skew in wild golden lion tamarins (Leontopithecus rosalia)

► All female golden lion tamarins became pregnant by 3.9 yrs of age. ► Two females became pregnant in 83% of groups with multiple adult females. ► Pregnancies by dominant females were 40 times more likely to succeed. ► 5 of 7 subordinate pregnancies reached full-term but infants were never observed. ► Subordinate reproduction was limited via behavioral, not hormonal mechanisms.