USING LABORATORY ROBOTICS, HIGH-THROUGHPUT SEQUENCING AND SAMPLING WITH VOLUNTEERS FOR QUICK AND COST-EFFECTIVE LARGE-SCALE GENETIC ESTIMATES OF BROWN BEAR POPULATION SIZE – TRANSBOUNDARY CASE STUDY IN SLOVENIA

Population size estimate is often very high on management and conservation agendas for many wildlife populations. The best currently available tool to obtain this parameter is noninvasive genetic sampling paired with mark-recapture modelling, which is now routinely done in many populations. However, in large populations where a lot of samples must be obtained if any meaningful estimate is to be had, the analyses can be very expensive and time consuming, often delaying results that are critical for management. We used laboratory robotics and recently developed genotyping methods that utilize high-throughput sequencing (HTS) to speedup the analyses and decrease costs. In anintensive three-month transboundary effort in autumn of 2015, in collaboration with ~2500 volunteers, we collected 4687 samples over the entire bear range in Slovenia and Croatia. After ironing out specifics related to automation of DNA extraction and processing of big data, the analysis was completed in roughly nine months. Increased throughput and lower costs allowed us to analyze 4370 of the collected samples, 45.7% more than we budgeted for. The population size in both countries at the end of 2015, after yearly mortality and before reproduction, was 1392 bears (1247-1583 95% CI), and sex ratio 58.9% F : 41.1% M. Since noninvasive genetics is increasingly becoming the go-to method for estimating the size of bear populations, there is a need for this to become fast and cost-effective. In this first large-scale study using HTS we showed that genotyping using this approach provides a big step in that direction, and we managed to do it with transboundary cooperation of two countries. In addition, the benefit of obtaining genotypes at the DNA sequence level makes the data completely future- proof and transferable between laboratories. Considering the rapid advances in DNA sequencing technology we feel that this is how such studies will be done in the future, for a fraction of the current costs.