Something unexpected is happening to sea turtles, and scientists can’t fully explain it

Sea turtle nesting study: On the beaches of Cabo Verde, more loggerhead sea turtle tracks in the sand might seem like good news. Over 17 years, researchers recorded 178,566 nests on Sal Island, one of the world's most important nesting sites for loggerheads. While the growing number of nests and earlier arrivals suggested that the population was doing well, when scientists looked more closely at individual turtles, they found a more complicated story.

By tagging 14,162 female turtles and following them over time, researchers discovered that females are now returning to breed less often and are producing fewer eggs when they do nest, as per a report.

Sea turtles are arriving earlier, but laying fewer eggs

The study found that warmer sea temperatures are causing loggerhead turtles to begin nesting earlier in the season, as per an Eco News report. In warmer years, turtles started, peaked, and finished nesting sooner than usual.


This shift shows that the turtles can adjust their behavior in response to changing conditions. However, researchers say that this flexibility may not be enough to offset other challenges.

While turtles are arriving earlier, females are nesting less frequently and laying fewer eggs overall.

Over the course of the study, the interval between breeding seasons roughly doubled, increasing from about two years to around four years. This means that although females still return to the beaches, they are contributing to the next generation less often.

The real problem may be happening far from the beach

Scientists believe the answer may lie far from the nesting beaches.

Loggerhead turtles are known as "capital breeders," meaning they rely on energy stored while feeding at sea to support migration and reproduction, as per the Eco News report. Females use these energy reserves to travel, dig nests, and lay eggs.

To understand what was happening, researchers examined chlorophyll levels in feeding areas off West Africa. Higher chlorophyll levels usually indicate a richer and more productive food web.

The findings suggest that poorer feeding conditions at sea may be reducing the energy available for reproduction. As a result, turtles may need longer recovery periods before breeding again.

Researchers also found declines in both clutch frequency and clutch size, meaning females are producing fewer nests per season and fewer eggs in each nest, as per the Eco News report.

More nests do not always mean a healthier population

The study highlights an important lesson for conservation. Counting nests on beaches can provide valuable information, but it does not always reveal the full health of a population. A beach may appear busy while individual females are slowly reproducing less over time.

Researchers say this means conservation efforts cannot focus only on nesting beaches, as per the Eco News report. Protecting feeding grounds in the ocean is equally important because those areas provide the energy turtles need to reproduce.

Scientists say there are still unanswered questions

The research does not suggest that loggerhead turtles have stopped adapting. Their earlier nesting behavior demonstrates that they can respond to environmental change.

However, scientists say there are limits to that flexibility. If warming seas and reduced food availability continue to affect reproductive energy, even large nesting populations could become more vulnerable over time.

For now, researchers say the unexpected combination of earlier nesting and lower reproductive output shows that understanding sea turtle populations requires looking both at what happens on the beach and what happens far out at sea, as per the Eco News report.

FAQs

Why are scientists concerned about these sea turtles?
Scientists found that female loggerhead turtles are returning to nest less often and laying fewer eggs.

Why are turtles producing fewer eggs?
Scientists believe poorer feeding conditions at sea may be reducing the energy females need for reproduction.