DOI: 10.5061/dryad.2547d7wvn
title: Three-dimensional time-resolved flash occurrences of swarming Photinus carolinus fireflies in their natural habitat

description: Photinus carolinus fireflies are famous for their synchronous
 display. Individual males emit flash trains consisting generally of 5 to 7
 flashes every 0.5s (approximately). Swarming males adjust the timing of
 their phrases on each other's tempo, thus collectively producing
 periodic bursts of synchronized flashes. P. carolinus populations are
 found primarily scattered along the Appalachian chain of the Eastern
 United States, notably in the Smoky Mountains. There, while observed by
 local residents since at least the 1960s, this spectacular phenomenon
 started being investigated with modern data collection techniques in the
 1990s. Starting in 2019, we have used high-resolution stereoscopic
 videography to capture the collective display of Photinus carolinus
 fireflies in their natural habitat, namely the Elkmont, Tennessee area of
 Great Smoky Mountains National Park. In this dataset, we provide the
 three-dimensional (3D), time-resolved coordinates of flash occurrences for
 several swarming events. The 3D data correspond to: 1) recordings made
 every night between June 3 and June 13, 2020 (except June 4 and June 6),
 at the exact same location in a small forest clearing; 2) recordings made
 using 360-degree cameras on June 9, 10 and 13, 2020 at two nearby sites.
 In addition, we are providing a complete set of the original movies for
 June 11, 2020. The dataset provided was the basis to the findings
 presented in: Sarfati et al., Self-organization in natural swarms of
 Photinus carolinus fireflies, Science Advances, abg9259
 (2021). We hope that it will foster further discoveries.
description: Recordings from June 3 to June 13, 2020:<br>Two Sony α7R4
 cameras were placed about 4m apart in a small forest clearing. The same
 area with the same field of view was recorded on each night, starting at
 9:15pm EST. The raw movies are available for June 11 (the cameras
 automatically create a second movie after 100min of recording). Camera
 settings: 60 frames per second (fps); exposure time 1/60s; maximum
 aperture (f/1.8); maximum ISO (32,000); and focus to infinity. Spatial
 calibration was performed using several pictures of a checkerboard (25 mm
 square side length) and the MATLAB stereo calibration toolbox. Flash
 positions in each frame were extracted by pixel intensity thresholding. 3D
 coordinates of recorded flashes were triangulated based on camera pose
 using MATLAB's triangulate function. About 60% of the flashes
 recorded in each camera could be triangulated. Outlier points (about 1%),
 for example those falling out of physical range, were removed in
 postprocessing. Recordings using 360-degree
 cameras:<br>Two GoPro Fusion 360-degree cameras recording at 30 fps
 were placed on the ground at a set distance (0.9 or 1.8 m) facing the same
 direction. The cameras were started at around 9:30 p.m. EST (Eastern
 Standard Time) each night at two different locations. They recorded for
 about 100 min. 
description: .MP4 files can be opened with any standard video
 player<br>.csv files can be opened with any standard CSV
 reader<br>.mat structure files should be opened with
 MATLAB