Sea Turtles

Pixabay / Public Domain
Pixabay / Public Domain

Why marine creatures swim in circles

Thanks for advancements in tracking technologies, scientists have discovered an intriguing behavioural trait amongst some marine species: They sometimes swim in circles.

When studying the navigational abilities of sea turtles, Tomoko Narazaki, a marine researcher at the University of Tokyo, observed that the turtles in her study would swim in circles so constantly “just like a machine.”

Sea turtles to spend more time house-hunting in the future

In the future, sea turtles in the US will find it harder to find suitable nesting habitat, due to climate change, rising sea levels and coastal development.

A team led by Florida State University came to this conclusion after their research which modelled the suitability of coastal habitats in the eastern United States by 2050 for sea turtle nesting, after considering predicted sea-level rise and future climates.

Their findings were recently published in the Regional Environmental Change journal.

Baby loggerhead

Do young loggerhead turtles swim or drift?

Despite good swimming abilities, juvenile loggerhead turtles are thought to drift passively for a significant portion of their existence on the high seas

However, a study by researchers from National Oceanic and Atmospheric Administration has found that turtles were swimming against the prevailing current in a statistically significant pattern at a rate of 30 cm/sec, which indicates an ability to detect the current flow and orient themselves to swim into the current flow direction.

This study provides (...) compelling evidence that these turtles are able to resist such transport using some mechanism not yet fully understood.

—Dr. Donald Kobayashi, National Oceanic and Atmospheric Administration

Turtles and plastic bags
Plastics floating in the ocean build a coating of algae and microorganisms that smells edible to turtles.

Why do sea turtles eat plastic? Perhaps because it smells good

To understand sea turtle behavior around ocean plastics, the research team compared how sea turtles in a lab setting reacted to smelling odors of turtle food, ocean-soaked plastic, clean plastic and water.

The turtles ignored the scents of clean plastic and water, but responded to the odors of food and ocean-soaked plastics by showing foraging behavior. This included poking their noses out of the water repeatedly as they tried to smell the food source, and increasing their activity as they searched.

Study identifies key loggerhead turtle foraging grounds

After tracking female loggerhead turtles in the Mediterranean, scientists at University of Exeter discovered that they feed at the same locations every year.

Specifically, these were in the Adriatic region, Tunisian Plateau and the eastern Mediterranean. Unfortunately, some of these locations are not ideal, and lead the loggerheads into danger.

Sea turtles’ magnetic sense

This behaviour seems to imply a map sense from which the creatures read either absolute or relative location from at least two coordinates. The direction is one thing but how about the position?

Latitude is fairly simple to judge, and there is good evidence that animals have this variable well under control. The elevation of the pole point at night, for example, gives the latitude directly; memorizing the constellations allows at least some species to infer the pole point through broken clouds.

The results demonstrate for the first time that longitude can be encoded into the magnetic positioning system of a migratory animal. Because turtles also assess north-south position magnetically, the findings imply that loggerheads have a navigational system that exploits the Earth’s magnetic field as a kind of bicoordinate magnetic map from which both longitudinal and latitudinal information can be extracted.