Satellites Over Seals (SOS) is a crowd-sourced, remote sensing approach to identify presence/absence patterns of the Weddell seal (Leptonychotes weddellii), and has recently been adapted for crabeater seals (Lobodon carcinophagus) in the Weddell Sea region. Satellites Over Seals provides an efficient method to screen large numbers of images (and hence area) for undertaking census counts of Weddell and crabeater seals.
Using high-resolution satellite imagery (VHR; 0.3–0.6 m resolution) and the online platform, Tomnod, to host VHR for the public (i.e. “the crowd,”) to search, we collected presence/absence data for Weddell seals on images from November 2010 and 2011. In a second campaign, we selected images of the pack ice acquired during October 2018 in the Weddell Sea to identify presence/absence of crabeater seals.
In both campaigns, our goal was to identify probable presence/absence to learn where closer inspection — and abundance estimation — should be concentrated. More than 325 000 citizen scientists searched 852 VHR images, composed of a series of tiles called “maps”, across both campaigns. The circum-Antarctic search for Weddell seals covered 268 611 km2 of fast ice continent-wide and the crabeater seal campaign covered about 18 000 km2 of pack ice. Using consensus-based algorithms on images identified by the crowd to have seals present, we identified Weddell seal presence on only 0.55% of maps (total n=1 116 058) within the available fast ice during 2010 and 2011.
Preliminary data on crabeater seal presence in the Weddell Sea region suggested presence on 3.3% of maps. Comparison with images searched by experts showed that the rate of false negative detections for Weddell seals was low (1.7%), although false positives were high (67%). The crabeater seal detections (3.3% of maps with seal presence) reported here were conducted by experts, and on a subset of available images (of area totalling 738 km2).
We assess image resolution, quality, training and outreach for future campaigns, and effectiveness of implementation toward encouraging remote sensing and citizen science as solutions to learn about Southern Ocean predators.