Erratum to: Seasonal Variation in the Activity and Dietary Budgets of Cat Ba Langurs (Trachypithecus poliocephalus) (International Journal of Primatology, (2016), 37, 4-5, (586-604), 10.1007/s10764-016-9923-z)

Primate activity budgets are dictated by food availability and distribution, thus primates living in seasonal environments must adapt their behaviors to accommodate fluctuations in resources. Cat Ba langurs (Trachypithecus poliocephalus), a Critically Endangered Asian colobine and a member of the limestone langur group (francoisi superspecies group within genus Trachypithecus), live only in fragmented and disturbed habitats on Cat Ba Island, northeastern Vietnam. This study aimed to assess the behaviors and diet of Cat Ba langurs by group, age, sex and season.We predicted theywould have high proportions of inactivity and foraging, low proportions of social behaviors, with seasonal variation that reflects an energy maximising strategy.We conducted behavioral observations through scan sampling over an 11 month period and found that Cat Ba langurs spent a significant portion of their day inactive (55 ± 1.3%) followed by foraging (19 ± 1.1%), locomoting (12 ± 0.9%), engaging in social behavior (12 ± 0.7%), and engaging in ‘other’ behaviors (2 ± 0.2%). Their diet was made up primarily of leaves (84 ± 2.8%) followed by fruit (8 ± 2.8%), flowers (5 ± 1.7%), and stems (3 ± 1.2%). Activity budget differed between groups, which is likely due to differences in demographics and home range between groups. Seasonally, the animals ate more leaves and spent more time foraging in the dry season than the wet season, suggesting that they are energy maximisers. Cat Ba langurs have similar activity and dietary budgets to other limestone langurs, and respond to a presumed seasonal fluctuation in food availability similarly.