Home range size and sleeping site use by the Critically Endangered Cat Ba langurs (Trachypithecus poliocephalus)

Abstract

Home range size and habitat utilisation are affected by access to key resources including food, water and sleeping sites, all of which change seasonally. Limestone langurs (a group within the Trachypithecus genus) live on limestone karst hills with shrubby, stunted, and discontinuous vegetation. This study assesses home range size and sleeping site use in two groups of Critically Endangered Cat Ba langurs (Trachypithecus poliocephalus). Over 180 days of observations, we found that the larger group (n=10-13) had a home range size of 50ha, while the smaller group (n=7) ranged within a 22ha area. There was also a small 5 ha area of home range overlap, which represents 10% of the larger group and 24% of the smaller group’s home range; although this area was not used at the same time. Home range sizes increased in the wet season, which may for fruit, which is eaten more at this time of year. Most sleeping sites were ledges (61%) followed by caves (17%), however the caves that were used seemed to be preferentially chosen. Sleeping sites did not vary seasonally. The lack of reuse on consecutive nights indicates they may be chosen to provide safety from predators (primarily study of this highly threatened species to assess patterns of home range use and sleeping sites. This is key to conservation management plan-ning as it can provide a measure of habitat use, which has implications long term viability.