Fig 1.
The complete workflow to compile individual images from a July 5, 2019 drone flight into an orthomosaic for citizen science and expert counts (18,366 animals).
Fig 2.
(A) A screenshot from the "classify" tab of the citizen science website (sealcount.com) with additional drone photographs of (B) elephant seals and (C) sea lions for illustrative purposes. Users are asked to select "seal" or "sea lion" and click once on each animal’s head to count it. All volunteers have access to a tutorial and field guide with detailed instructions for animal identification.
Fig 3.
Comparison of percent error for (left) six algorithms for all photographs and (right) based on the number of citizen scientists that counted each photograph (number of photographs provided in parentheses).
Algorithms using the Median consistently outperformed those using the Mean, especially for elephant seals. Because scientists tended to underestimate sea lion abundance, the most accurate counts were obtained using many repeated counts and removing the lowest two values before calculating the Median.
Fig 4.
Comparison of raw citizen scientist counts against expert counts for three algorithms.
Citizen scientists tended to underestimate the actual number of pinnipeds present on Año Nuevo Island, as evidenced by the slopes <1 for all algorithms and species except for Median[3:Max] with elephant seals (bottom left). Colored lines represent a linear model for each algorithm and species combination, whereas black lines represent 1:1 relationship between citizen scientist count and expert count.
Fig 5.
Counts for each drone flight date by an expert as compared to the three Median algorithms for summarizing citizen science counts.
Sea lions were not counted during the two winter flights due to extremely low abundance. An asterisk denotes the citizen science algorithm (Median) that best matches the expert counts across all flights.
Fig 6.
The total number of elephant seals counted by experts (black points) as compared to citizen science counts using the Median[3:Max] algorithm (pink points).