12 years after an oil spill covered almost 35 miles of the Kalamazoo River, new research from the University of Toledo shows that turtles that were rehabilitated after the disaster had a high chance of living for a long time.
After an Enbridge pipeline broke near Marshall, Michigan, in July 2010, 843,000 gallons of oil spilled into a river’s tributary creek. This was the largest inland oil spill in U.S. history. Turtles were the animals most often found with oil on them.
Nearly 8% of the northern map turtles that were recovered from the spill perished right away.
Josh Otten, a biologist who received his Ph.D. in biology from the University of Toledo in May, was one of the first environmental responders on the scene and is the lead author of a recent study that was published in the journal Environmental Pollution.
As a doctoral student in the lab of Dr. Jeanine Refsnider, associate professor in the UToledo Department of Environmental Sciences, Otten assisted in organizing efforts to rescue, rehab, and release thousands of injured turtles in 2010 and 2011. Eight to eleven years after the oil spill, she went back to see how the turtle population was doing.
In the 14 months after the spill, he found that the rehabilitation process made it much more likely that northern map turtles would live each month. This showed how important and effective oil removal from turtles is.
Additionally, the success is sustained over time. Eleven years after the spill, there was almost no difference between the turtles who were affected by the spill and those who were not.
In order to increase turtles’ chances of surviving after a significant oil spill disaster, Otten said that it is crucial to invest time, money, and effort in their rehabilitation process. “Eight to eleven years after the oil spill, the northern river turtle population in the Kalamazoo River appears to be healthy and stable.”
He claimed that between 2018 and 2021, a sizable number of adults, juveniles, and hatchlings were captured and recaptured, indicating population growth. Additionally, there are high monthly survival rates during this time.
Following a natural disaster like an oil spill, saving and rehabilitating individual animals is a fairly common practice. “It frequently serves as a means for volunteers and other locals to feel as though they are contributing to the solution,” said Refsnider. However, efforts to rehabilitate animals can be very costly and time-consuming, and very few studies examine whether they are actually effective in raising survival rates for those who have undergone rehabilitation. This is one of the few studies to have directly measured the survival rates of animals following cleaning and rehabilitation as a result of a significant oil spill. ”
To understand how the turtle population is doing today and to identify specific turtles that have been saved and rehabbed during oil spill cleanup operations in 2010, Otten’s Ph.D. research involved extensive recapture, radio-telemetry, and nest-monitoring efforts.
“The scale of Josh’s study is really unprecedented — he handled several thousand turtles on nearly 50 kilometers of river over the course of this study and amassed an enormous dataset of capture histories and locations for turtles over a 10-year period,” said Refsnider.
The U.S. Fish and Wildlife Service helped fund the turtle population study, which focused on northern map turtles and estimated the monthly survival rates of turtles exposed to the freshwater spill for up to 14 months after the spill and again for 8–11 years after the environmental disaster.
2,100 northern map turtles affected by the spill were caught in 2010 and 2011, cleaned up, given rehabilitation, marked, and then released into the Kalamazoo River.
63% of them were only ever taken once.
Otten said, “The likelihood that I would recapture them is quite low. “Northern map turtles can be challenging to capture to begin with.” “You must also take into account additional factors like emigration, translocation, and natural mortality. There are undoubtedly a good number more that have evaded capture during the four years I conducted my survey. The recapture rates are quite good in terms of long-term turtle survey projects and detectability.
Unlike mammals and birds, which typically die after a few weeks, northern sea turtles, which can live up to 60 years, can survive after being oiled for months.
According to the study, turtles may have a delayed reaction to an oil spill because they typically die nearly 60 days after being captured during the rehabilitation process while under the care of veterinarians.
Otten says that this shows how important it is to keep helping animals after a spill, especially if turtles are involved.
Following the Kalamazoo River oil spill, the researchers discovered that northern map turtles that had undergone any form of rehabilitation had a significantly higher monthly survival rate than those that had not. They also found that the turtles that spent the most time in rehabilitation from September 2010 to May 2011 while people worked to clean up the river had the highest monthly survival rate in the 14 months after the spill.
Regarding how oil in general affects the environment, Otten said, “There are so many unknowns.” “We don’t know if there may have been a change in the availability of food, whether oil pooling in turtles’ wintering grounds affected their ability to survive, or even how cleanup activities like boat traffic and eroding shorelines may have affected turtles. Due to these factors, it is crucial to carry out research like this years after a disaster to spot trends and advise researchers, cleanup teams, and government organizations on how to best use their time and resources.
