LIGHTSCAPES OF FEAR
Behavioral Rest at Sea
This interactive map displays the tracks, trip duration, and dive metadata for 8 of the 71 female northern elephant seals we incorporated in a recent study investigating the risk-reward tradeoffs of behavioral rest at sea.
Data from time-depth recorder and satellite instruments were processed in MATLAB and converted into KML files. Individual KML files were imported into a single KMZ zipped file to be imported into Google Maps' "My Maps" tool, which allows users to quickly and flexibly build interactive map interfaces. Metadata was exported from MATLAB into a CSV which was then paired to the data layer containing each respective animal's track. This interactive data visualization was created to accompany our latest publication in Science Advances "Lightscapes of Fear: How mesopredators balance starvation and predation in the open ocean".
Map, infographics, and cover art by Jessica Kendall-Bar. Data analysis by Roxanne Beltran.
Illustrations by Danielle Dube, Art-Science Residency with the Norris Center for Natural History.
PICK A SEAL
Click on a female northern elephant seal's track in the interactive map below to learn more about her journey into the North Pacific. You'll learn her TOPPID (a unique animal ID given to any migrating top predator as part of the TOPP program), trip duration, departure date, arrival date, number of rest dives, and total number of dives.
FOLLOW HER JOURNEY
While at sea, elephant seals perform a number of distinct dive types: transit dives (U-shaped dives where they continuously swim), benthic dives (dives where they travel along the bottom), foraging dives (where they capture prey in the water column), and drift dives. Drift dives are dives where they swim down to 200-300 meters, turn upside down, and drift for several minutes before they swim back to the surface. We think that these animals could potentially be sleeping during these restful drift dives, so we wanted to look at their resting behavior across the foraging trip.
As the seal gains more and more body fat, her body composition starts to shift and she becomes less dense. One day, once she's gained enough fat to become positively buoyant, she starts to float up to the surface instead of sink down to the safety of darkness. You can imagine how alarming this must be for a sleepy elephant seal trying to avoid visual predators which hang out near the surface (like white sharks and killer whales).
So, she decides to switch her strategy. She shifts her sleep schedule earlier so that she can sleep in the safety of darkness, sacrificing some valuable hours of nighttime foraging which she no longer desperately needs given her growing fat stores. She also begins her drift dives deeper so that she ends up at about the same depth as if she were negatively buoyant. By tracking her buoyancy over time, we are able to track her risk-taking behavior over several months out at sea.