September 1, 2020 — The following was released by NOAA Fisheries:
In early June 2011, NOAA Fisheries researchers and colleagues placed satellite tags on 26 loggerhead sea turtles in the Mid-Atlantic Bight. The tagging was part of ongoing studies of loggerhead movements and behavior. The Mid-Atlantic Bight, off the U.S. East Coast, is the coastal region from Cape Hatteras, North Carolina to southern Massachusetts. A little more than 2 months later, on August 28, Hurricane Irene passed through the area, putting 18 of the tagged turtles in its direct path. The researchers were able to track changes in the turtles’ behavior coinciding with the hurricane, and found that they reacted in various ways.
“Hurricanes are some of the most intense weather events loggerheads in the mid-Atlantic experience, and we thought it was worth investigating how turtles in our dataset may be influenced by these dramatic environmental changes,” said Leah Crowe, a contract field biologist at the NOAA Northeast Fisheries Science Center’s laboratory in Woods Hole, Massachusetts, and lead author of the study published recently in Movement Ecology. “It was a perfect storm situation in terms of location, timing, and oceanographic conditions. We found that the turtles responded to the changes in their habitat in different ways.”
Satellite tags attached to a turtle’s carapace, or shell, transmitted the turtles’ location and dive behavior. They also recorded sea-surface temperatures and temperature-depth profiles for approximately 13 months. This enabled the researchers to investigate the movements of 18 juvenile and adult-sized loggerhead turtles and associated oceanographic conditions as the hurricane moved through the region.
Most of the turtles moved northward during the hurricane, aligning themselves with the surface currents — perhaps to conserve energy. Researchers observed longer dive durations after the hurricane for turtles that stayed in their pre-storm foraging areas. Some dives lasted an hour or more, compared with less than 30 minutes for a typical dive before the storm.
The turtles that left their foraging areas after the hurricane passed moved south earlier than would be expected, based on their normal seasonal movements. This change was also more than a month earlier than the typical seasonal cooling in the water column, which is also when the foraging season for loggerhead turtles ends in the Mid-Atlantic Bight.
“Loggerheads experience environmental changes in the entire water column from the surface to the bottom, including during extreme weather events,” said Crowe. “This study was an opportunistic look at turtle behavior during a hurricane. Their behavior makes loggerheads good observers of oceanographic conditions where they forage.”