Data Sampling Options for Animal-Borne Video Cameras: Considerations Based on Deployments with Antarctic Fur Seals

Although the use of animal-borne video cameras has brought great insight into the lives of animals, there are still several limitations in using them to record observational data. The ethical demand for reduced camera size limits battery capacity, which thus restricts recording duration. In addition to design considerations, there are several sampling options available for extending sampling duration following tag deployment. These options include the use of duty cycling (for sampling at preset times), a depth trigger and varying the sampling interval between images. We investigate the consequences of these options based on foraging data collected from Antarctic fur seals using the Venus camera system (Wild Insight Ltd). We show the effect of differing sampling protocols on the resulting data. By sub-sampling our dataset, we show how changes in sampling protocol affect the number of prey images collected and the measurement of simple foraging variables such as the time spent feeding. In addition, we ran simulations based on altering the foraging parameters: prey-encounter rate (waiting time) and handling time (feeding event duration), to more broadly investigate how changes in sampling frequency would impact data collection for species with varying foraging characteristics. We show that, irrespective of sampling frequency, the proportion of prey images recorded remains constant, suggesting that coverage of a foraging trip could be extended for investigation of time-invariant processes by using an increased sampling interval. Measurement of rates or durations of behavioral events (such as prey-encounter rate or handling time), however, requires higher sampling rates to increase the precision of parameter values.