This fall and winter, from the end of October to the end of January, a total of 480 cold-stunned sea turtles stranded on bayside Cape Cod beaches. Three hundred and ninety-four of those sea turtles were Kemp’s ridleys, the most endangered sea turtle species in the world. In addition, 55 loggerheads and 30 green sea turtles (and 1 possible loggerhead-Kemp’s ridley hybrid) washed up and were found by beach walkers, trained volunteers and Mass Audubon staff.
Two years ago, the 2014 cold-stun season really caught peoples’ attention with a record-breaking 1,241 stranded sea turtles that winter. Then, the second largest number of sea turtles stranded during the 2015 season, with 613 turtles found on bayside Cape Cod beaches. That makes this year the third largest cold-stunned sea turtle stranding season on record.
The line graph below shows the total number of stranded sea turtles each day for the past three stranding seasons, allowing us to compare when the most sea turtles washed up each year. As you can see, there was a major spike that lasted several days in 2014, with up to 200 sea turtles stranding on a single day in November. In 2015, there was another noticeable spike with 100 turtles stranded on December 20th. Luckily for our volunteers and staff in 2016, the largest number of turtles we retrieved in one day was 57 on December 10th during a relatively busy period.
Sea turtles are generally elusive creatures and their location at any given moment in time can be difficult to predict. However, we know that the water temperature in Cape Cod Bay, as well as the wind’s speed and direction, help dictate when and where sea turtles will strand each winter.
Every year as winter approaches and the bay’s temperature gradually drops close to 50°F, sea turtles still in the bay from summertime feeding become too cold to swim and their normal bodily functions begin to slow down. This allows cold-stunned sea turtles to be pushed around by the bay’s currents and waves. Since waves are controlled by the wind, sea turtles are most likely to wash up on beaches when it is very windy, and we can roughly predict where they will strand based on which way those strong winds are blowing.
As the bar graph below shows, the Cape Cod town with the greatest number of stranded cold-stunned sea turtles to wash up onto its beaches during the 2016 season was Brewster with 179. This is more than double what any other town received this season. As previously mentioned, looking at historical wind data might help us better understand the year’s dispersal of sea turtles. For example, 33 of the 57 turtles that stranded on December 10th were pushed ashore in Brewster, when there had been strong northwest winds with gusts over 30 mph for two days prior.
When added to all of our previous seasons’ data, this year’s spike makes Brewster the Cape Cod town with the most cold-stunned sea turtle strandings on record: a total of 827 turtles since 1999. After Brewster, Eastham and Wellfleet tie for second place. They have each had a total of 807 cold-stunned sea turtles strand on their beaches in the last 17 years. Truro comes in third with 701 cold-stun strandings since 1999. Of course, these numbers are partially dependent on the length of coastline attributed to each bayside town. Orleans, for example, receives a good number of stranded cold-stunned sea turtles each year, despite having a relatively short coastline with only two bayside beaches.
Now that spring is around the corner, the focus has shifted from rescuing sea turtles to getting them rehabilitated and released. Thanks to around-the-clock help from hundreds of dedicated individuals, most of the stranded sea turtles found alive (330 turtles, or approximately 70% of those stranded in 2016) survived long enough to get a second chance.
Every living, stranded sea turtle got treated by our friends at the New England Aquarium in their off-site rehab facility. Then, as turtles have become healthy enough to be transported, they’ve been periodically sent to other aquariums and rehab facilities farther south along the east coast. These lucky sea turtles, which once found themselves near death in the frigid waters of Cape Cod Bay and have been through so much since then, will soon find themselves released into the subtropical waters they’ve surely been missing.
This post was contributed by turtle field researcher Olivia Bourque who’s starting to focus on diamondback terrapin nesting season in a few months!