 Studies suggest that slow lorises are polygynandrous . Infants are either parked on branches while their parents find food or else are carried by one of the parents . Due to their long gestations ( about six months ) , small litter sizes , low birth weights , long weaning times ( three to six months ) , and long gaps between births , slow loris populations have one of the slowest growth rates among mammals of similar size . Pygmy slow lorises are likely to give birth to twins — from 50 % to 100 % of births , depending on the study ; in contrast , this phenomenon is rare ( 3 % occurrence ) in Bengal slow lorises . A seven @-@ year study of captive @-@ bred pygmy slow lorises showed a skewed sex distribution , with 1 @.@ 68 males born for every 1 female . 
