 Traditionally , the slow lorises were thought to consist of very few species and were considered to be common across Southeast Asia . These assumptions were due to their nocturnal behavior and their high frequency of occurrence in animal markets throughout the region . Furthermore , researchers from the 20th century and earlier perpetuated the notion that slow lorises were common by reporting them as either present or absent rather than noting low population densities in their field research . As a result , slow lorises were seldom studied , resulting in the initial " Lower Risk / least concern " ( LR / lc ) conservation status assessment on the IUCN Red List ( version 2 @.@ 3 ) in 2000 . Even in the mid @-@ 2000s , population estimates were based only on small surveys . 
