Final report for the NOAA ORTA Bridging Program Project: an Extension of 2020-05 monitoring body condition of seals in Alaska using small UAS

The recent and rapid environmental changes in the Subarctic and Arctic due to a warming climate have increased concern about the health, ecology, and abundance of pinniped populations in the region. Ice-associated seals (bearded (Erignathus barbatus), ringed (Pusa hispida), spotted (Phoca largha), and ribbon (Histriophoca fasciata)) are key components of subarctic and arctic ecosystems in Alaska, and long-term monitoring has indicated that the body condition of some of these populations has declined in recent decades. Traditional methods of capturing and measuring individuals to assess body condition of these populations are challenging and constrained by small sample sizes; therefore, our goal was to develop a method to expand the numbers of individuals that can be monitored. We used an uncrewed aerial system (UAS) to collect imagery of bearded, ringed, and spotted seals at captive care facilities, and used photogrammetry of the UAS images to develop a model to estimate body mass to use as an indicator of body condition. We collected measurements from the UAS images, which were taken with the UAS directly over the seals with the camera at nadir.