Validating Dynamic Body Acceleration metrics as a measure of energy expenditure in a Neotropical primate

Quantifying energy expenditure in free-living primates is fundamentally important yet challenging. Acceleration-based metrics such as Dynamic Body Acceleration (DBA), obtained from accelerometers, are potential proxies for energy expenditure, yet have not been previously validated in primates. Here, we validated DBA in black lion tamarins ( Leontopithecus chrysopygus ) by comparison to doubly labelled water (DLW) in 10 captive tamarins housed at the Rio de Janeiro Primate Centre. Individuals were equipped over 48 hours with a backpack with a tri-axial accelerometer and received an intra-peritoneal DLW injection at the beginning of the experiment, with blood samples taken 1 and 48h later. Daily Energy Expenditure by DLW was 326 (SD=66) kJ/day, close to expected values for primates of their size. The accelerometers recorded at 40 Hz, collecting >6.9 million records per axis for each individual. Individual DBA metrics were calculated and regressed against DLW daily energy measures. From this regression, we found a consistent and significant linear relationship (R2 = 0.46) between DLW and DBA, which could be improved by the incorporation of activity and resting time information (R2 = 0.52). Our results provide the first estimates of total daily energy expenditure for black lion tamarins and a validation of the method for estimating energy expenditure through accelerometers. Given the similar levels of total energy expenditure of captive and wild primates, this method can now be used in the field to estimate the energy cost of black lion tamarin movements in its natural environment. 1 Summary statement Dynamic body acceleration was validated against doubly labelled water in black lion tamarins, showing it is a useful tool for measuring free-living energy demands. ### Competing Interest Statement The authors have declared no competing interest. * AIC : Akaike Information Criterion BLT : black lion tamarin BM : body mass DBA : Dynamic Body Acceleration DD : Daily Diary (device) DDMT : Daily Diary Multiple Trace Graphing Tool (software) DEE : Daily Energy Expenditure DLW : Doubly Labelled Water EE : Energy Expenditure ODBA : Overall Dynamic Body Acceleration RMR : Resting Metabolic Rate sODBA : smoothed Overall Dynamic Body Acceleration sVeDBA : smoothed Vectorial Dynamic Body Acceleration TEE : Total Energy Expenditure VeDBA : Vectorial Dynamic Body Acceleration