Mammals of Chitwan National Park and its surroundings: An account from Camera Trap Survey
ABOUT SURVEY
This book is based on information obtained from camera trapping surveys during the national tiger and prey base survey in 2022. The detailed method followed for the field survey is described in the tiger and prey base monitoring protocol (DNPWC, 2017).
A total of 505 camera-trap grid cells was set with a spacing of 2 km in Chitwan National Park and adjoining forests. Due to limited availability of camera-traps and logistical challenges, the survey area was divided into 3 blocks that were surveyed successively. Prior to camera deployment, intensive sign surveys were conducted to identify potential survey sites to increase the probability of photographing tigers/leopards and maximize camera safety. Motion sensor cameras (Cuddeback C1, Panthera V4, and Stealth camSTC-DS4K) were installed at 45 cm above ground, perpendicular to, and 5-7 meter on either side of game trails, forest roads, and riverbeds without using any bait or lure. Camera traps were mounted on trees or on wooden poles and checked at least twice in a week. These motion sensor cameras were set to take three pictures per trigger with no delay between the triggers to ensure complete capture of animals. Photos obtained in camera traps were systematically sorted according to species for further analysis.
Number of locations where the species was captured, number of independent detections (60 min interval) and the detection rate (per 100 trap days) for each species were calculated from the camera trap photographs. For this calculation we only used the camera trap records of the species within CNP and its surrounding during 2022 survey. The Detection rate for species photographed in 2018 and 2022 survey was calculated using the following formula.
Detection rate (per 100 trap nights) = Number of independent detections of a species (x) 100 [divided by] Total effort (trap days) of the entire survey
The survey focused on capturing tigers/leopards through camera traps, the method adopted may not be adequate to represent the actual status of all terrestrial mammals present in the park. Particularly small mammals, primates, and species with specialized habitats and behaviour may be underrepresented. Arc GIS 10.8 was used to produce the distribution maps and frequency of species occurrence. Species occupancy was estimated only for 2022 survey using the Bayesian occupancy framework in the Camera Trap Management and Analysis Package(ZSL-CTAP). Some species photographed in camera traps between 2010 and 2021 but not captured in 2022 have also been included.
RESULTS
The total 86 mammalian species is known to occur in CNP, this survey recorded 36 medium-to-large sized species from camera trap surveys in 2018 and 2022. Among these recorded mammals 15 are listed as globally threatened and 20 nationally threatened species. However, the 2022 camera trap survey captured 32 mammals in a total effort of 8529 days in 505 camera trap locations. Honey badger, Chinese pangolin, Clouded leopard and Four horned antelope were detected in 2018 but not in 2022 survey.
