Sea Turtle Patrol at Night
Photo: Cheryl King

Dark Skies Save Sea Turtle Lives!

It’s sea turtle nesting season in many parts of the world, so turtle patrollers are busily searching for nesting female turtles to tag and nests to mark.  Here in Hawaiʻi, the first green (Chelonia mydas) nest will be recorded any day now, but hawksbills (Eretmochelys imbricata) typically start nesting about one month later.  Sea turtles usually return to the same geographical area where they were born, but that’s just the start of the search.  The following “turtle friendly” beach qualities are essential for them to be safe during the nesting process, and for their hatchlings to develop and survive to reach the ocean safely:

  • Quiet (no people, dogs, cars, loud noises, etc.)
  • Safe (away from the road, no vehicles driving on the beach, no nearby fishing activities, poaching, etc.)
  • Accessible sandy dunes, above the high tide line (not blocked by rocks, logs, seawalls, stairs, beach chairs, tents, boats, trash, etc.)
  • Native vegetation (no invasives with roots that are impenetrable by nesters, that extract moisture from eggs or that trap/entangle hatchlings)
  • Low predation rate and no introduced species like mongoose
  • Quality of the sandy nest (trash free with a complicated mixture of suitable moisture, temperature, grain size, sedimentation levels, oxygen flow, etc.)
  • Not prone to erosion or storm events
  • Dark (no lights from vehicles, buildings, streets, signs, flashlights, campfires, skyglow, etc.)

All of these nesting beach qualities are tough for a turtle to find, nowadays.  The easiest way for coastal residents and vacationers to help these turtles is to manage lighting.  There are some catchy phrases circulating nowadays to educate folks, which are often found printed on stickers or other reminder items in beachfront areas:

  • “Lights out- sea turtles dig the dark”
  • “After nine, it’s turtle time”
  • “Sometimes it’s nice to be left in the dark”
  • “Turn off the glow to help turtles go”

A bright condo lights up the night sky.

Why are our lights such a problem?

Sea turtles can actually see more shades within the color spectrum, including ultraviolet, than us.  Laboratory studies have shown that during seafinding, they are more attracted to shorter wavelengths (blues and greens) than the longer wavelengths (ambers and reds).

Of course, many other factors are involved like the intensity/brightness of the light source, but this is why sea turtle biologists use dim, red flashlights. It’s not that they don’t see our red lights- they just don’t react to them as much.

Although sea turtles don’t see nearly as well once on land as they do in the ocean, they still heavily rely on their vision when they’re crawling ashore to lay their eggs.  Bright lights not only deter them from nesting (which actually can be a good thing if these lights are always on since they’re sure to disorient the hatchlings once they emerge), but lights can also misorient them when they’re trying to return to the ocean again.  There are too many cases each year in which sea turtles end up in backyard swimming pools or get run over on beachside roads. Lit stretches of beach limit potentially important nesting habitats and condense the nesting activities to the darker areas instead of being spread out.  This can concentrate land and sea predators, raising mortality rates.

For hatchlings, lights are death traps since they override their ingrained behavior to crawl towards the brighter, open horizon (the ocean) AND away from tall, dark silhouettes (trees and other natural vegetation).  These visual cues, regardless of the presence, absence, cycle, or position of the moon, should always lead them to the ocean. These same instincts guide them during the day too!

Instead, like a moth to a flame, these tiny turtles will waste valuable energy crawling towards a light or the glow in the sky from multiple lights, such as in a city or even just a lighted parking lot or stadium.  Here, they lay victim to predation and exhaustion in addition to many other types of human-related dangers.

Most regions have lighting ordinances in place to protect sea turtles and other wildlife.  Our night skies are also negatively affected by light pollution, so astronomers are certainly onboard with dark sky initiatives.  April 15-21 was “International Dark Sky Week” to raise awareness.

Want to help?  It’s simple!

  • Keep the wavelengths of your outdoor lights in the longer spectrum (more reds and ambers, which will help your night vision too).
  • Reduce their intensity, point them down, shield them, and put them on timers or motion detectors.
  • Don’t forget to close your curtains. If you’re able to see your house lights from the beach, the turtles can too.
  • Let us all enjoy the stars!

Tauzer the dog with a lights out welcome mat. (Dark Skies Save Sea Turtle Lives)

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