Circadian Animals

Circadian System in Animals - Learning Objectives

• Do animals have Circadian Cycle?
• What are examples of animals being harmed by nightime lighting?
• Does light pollution change the behavior of animals?
• How to protect the turtles from night time lighting?

The sun plays an important role in the biological clocks of animals and plants. From the longest to the shortest day of the year,  the progression of more and less daylight provides important biological cues for all living things.

Animals Circadian Clocks

Animals and plants also have natural Circadian clocks regulating growth and biological processes.
The vast range of influences on all types of animals and plants is only beginning to be recognized. From nest choice and breeding success of birds to behavioral and physiological changes in salamanders, many organisms are seriously affected by human alterations in natural patterns of light and dark.
Animals exposed to light pollution will delay their foraging and hunting for several hours after dark, and wait until they have extreme hunger, to begin searching for food. This disruption in their natural cycles creates an imbalance in their biological systems.
Many animals grow warmer coats in winter, their fur coats stimulated to grow by the shorter daylight hours with the coming of winter, not the chilling temperatures.

Ecological Consequences of Artificial Night Lighting

Ecological Consequences of Artificial Night Lighting is the first book to consider the environmental effects of the intentional illumination of the night. It brings together leading scientists from around the world to review the state of knowledge on the subject and to describe specific effects that have been observed across a full range of taxonomic groups, including mammals, birds, reptiles and amphibians, fishes, invertebrates, and plants.

For more information read the book Ecological Consequences of Artificial Night Lighting By Catherine Rich and Travis Longcore. [2]

Fireflys can't see their mates - Insects & Light

"Turn off outside lights at night. Fireflies use their flashing lights to signal each other, attract mates and warn of danger. While the science is still preliminary, it's likely that human light pollution can disrupt their flashes—making it harder for fireflies to find mates and breed. This leads to fewer fireflies mating and smaller numbers in subsequent generations. You can make your yard a haven for fireflies by turning off exterior and garden lights, and drawing your blinds at night so that interior light doesn't brighten your yard too much." How you can help the firefly.  [1]

Turtle Safe Lighting

Certain ecological problems associated with artificial night lighting are widely known - for example, the disorientation of sea turtle hatchlings by beachfront lighting.

When specifying beachfront lighting in turtle nesting habitats, choose  amber colored lighting of 570 nanometers or longer and shield the light to shine down, away from the ocean.

"Sea turtles have crawled onto beaches to nest for millions of years. It was once easy for hatchlings to find the ocean after emerging from nests because the brightest horizon was always the ocean, compared to the dark dune. Now, Florida’s coasts are lined with beachfront properties that can emit powerful, white light, which can cause sea turtles to crawl toward those lights (misorient) or crawl in circles on the beach (disorient). Based on consensus from a panel of sea turtle experts, around 100,000 sea turtle hatchlings are disoriented each year in Florida. They can end up in pools, decks, or even the road."  https://conserveturtles.org/project-overview-stc-beachfront-lighting-program/

myfwc.com/conservation/you-conserve/lighting/

Sea Turtle Lighting Guidelines 
http://myfwc.com/media/418417/SeaTurtle_LightingGuidelines.pdf

Sundial Bridge is a pedestrian bridge in Shasta California where nightime illumination has affected the fish migrations. ​

Vanity Lighting of Bridges

Chinook salmon count declined from 15,000 in 2004 to 824 in 2011 - 'Since the bridge opened to walkers and bicycle riders in 2004, the number of winter-run Chinook salmon returning to spawn in the Sacramento River has plummeted from over 15,000 fish in 2005 to 824 in 2011...  "Intense levels of artificial light slow or stop juvenile migration of salmon" on their annual trek to the Pacific Ocean, said Andrew Jensen, a DFW staff environmental scientist.  And when the young fish stop in the water under the lights, larger fish, such as rainbow trout, are there to eat them, Jensen said.'
http://archive.redding.com/news/state-wildlife-officials-say-sundial-bridge-lighting-may-be-hurting-salmon-ep-361600259-354020541.html/

2017 -  US Bureau of Reclamation-CVPIA 2017 Annual Work Plan - “Artificial night-time lighting at structures near water is believed to have adverse impacts on juvenile salmon by altering fish behavior and making the fish more prone to predation..."
www.ecosacramento.net/wordpress/wp-content/uploads/bsk-pdf-manager/2017_03_March_21_Light_On_River_240.pdf

Footnotes

1. ​www.firefly.org/how-you-can-help.html

Photo Credits

Firefly
By Katja Schulz from Washington, D. C., USA - Eastern Firefly, CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=40575678

Wildlife Lighting logo by Florida Fish and Wildlife Conservation Commission  
​
Sundial Bridge photo by David Weekly from Cupertino, CA, USA - https://www.flickr.com/photos/47565600@N00/61743631/

Related Topics

Circadian Explained... Light Therapy, Nightlights, Sleep, Blue Dimming Apps, Ecology of Night Lighting, Dark Sky, Color in Light