Marine biologists set out to track the long-distance travels of a little-studied color variant of the green sea turtle, and found the animals barely left home. In a study published June 29 in Frontiers in Amphibian and Reptile Science, none of nine satellite-tagged "yellow morph" green turtles left the Galápagos Marine Reserve during years of tracking.
The team, led by Dr. John W. Rowe of Alma College with Dr. Juan Pablo Muñoz Pérez of Universidad San Francisco de Quito, tagged seven male and two female yellow-morph turtles captured in 2015 and followed them for up to 418 days apiece. On average, each turtle's home range covered about 1,498 square kilometers — a strikingly small area for a species whose more common dark-shelled counterparts are known to swim thousands of kilometers to nesting beaches as far away as the western Pacific. Five of the tagged turtles stayed close to their capture sites; the other four moved between islands within the reserve, mostly during the cooler months from April to October.
Green sea turtles are renowned open-ocean navigators, which made the yellow morph's homebody behavior stand out. The variant — found among green turtles in the eastern Pacific and best known from the Galápagos — remains poorly understood; scientists still don't know whether it represents a genetically distinct lineage, a life stage, or simply a diet-driven trait, as outlets including SciTechDaily and BBC Wildlife's Discover Wildlife noted in covering the findings.
An Open Question
"None of our satellite-tagged turtles even left the Galápagos Marine Reserve over the three years."
Dr. John W. Rowe, Alma College
The researchers are careful about how far the finding can be pushed. With only nine turtles tracked for a portion of their long lifespans, the study cannot rule out rare or seasonal transoceanic trips that simply went undetected during the tracking window, and it can't say whether yellow-morph turtles never migrate or simply migrate less often than their darker relatives.
The team is now calling for genetic work to determine whether the yellow morph is a distinct lineage, along with expanded tagging efforts to build a larger sample. The answer could matter for how the reserve is managed: if yellow-morph turtles genuinely spend most of their lives within its boundaries, they may be more exposed to local threats — and more responsive to local protections — than the population's more mobile members.
