Are we there yet?: stress levels of two sea turtle species during transportation to release sites

Driving in bumper-to-bumper rush hour traffic and bolting through crowded airports to catch a flight are just a couple of the stressful ways that we humans get around. And the longer the journey, the more stressed out we tend to get. Despite the aforementioned tensions, our efficient transportation systems are very important for health-related travel, like moving patients to and from medical facilities. Sometimes, these passengers are wild megafauna. How stressed do these animals get during ground transportation, especially if they are marine and “totally out of their element”? Does the length of the road trip matter?

Cape Cod, MA is known for its scenic views of the Atlantic Ocean, rustic beach architecture, and, unfortunately, a rising number of sea turtle strandings that exceed an average of 100 animals every autumn. Most of these turtles are hypothermic, or “cold-stunned”, and luckily have good recovery rates in rehabilitation. By the following spring they are ready to rejoin the Deep Blue; however, since the northeastern coasts are still cold at that time of year, they are transported south along the eastern seaboard for release in warmer waters.

Kemp’s ridley release. Photo credit: New England Aquarium.

Dr. Kathleen Hunt from the Smithsonian-Mason School of Conservation participated in a multi-institution collaboration to examine just how stressed juvenile Kemp’s ridley and loggerhead sea turtles (Lepidochelys kempii and Caretta caretta, respectively) get during ground transportation. Specifically, they investigated the potential impacts of travel duration and interspecific differences in stress sensitivity. Once the turtles had been rehabilitated for several months, and were deemed physiologically stable, they were secured in padded crates and driven to various locations for release. Hunt and coauthors sampled blood before and after the trips, which ranged from around 6-24 hours, to measure stress identifiers such as corticosterone, glucose, white blood count, and H/L ratios (heterophils/lymphocytes). They found that both species became more stressed with increasing travel duration, although the loggerheads were comparatively more sensitive at any given drive time. Data suggest that stress is tied to the noise, vibration, and general discomfort associated with travel rather than human handling throughout the process.

The authors propose that despite the spike in stress levels during travel, the current sea turtle transportation protocol is safe from a clinical perspective, although streamlining logistics and time reduction are key considerations. This study highlights the variable interspecific responses and sensitivity to stimuli that can occur within a taxa, and the important applications for animal rehabilitation efforts. Because unlike us, sea turtles, or any other fauna for that matter, can’t nag with “are we there yet?”

Danielle Ingle is a functional morphologist, biomechanist, and PhD candidate at Florida Atlantic University. Her research interests include the form and function of aquatic mammal and shark vertebrae as well as skeletal deformities in sea turtles.

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