Ask an Expert – Holiday Lighting May Not Be So Jolly for Wildlife

Author: Terry Messmer

The holidays are here and the holiday lights are bright. Although this lighting tradition brings joy to many, it can be considered a source of light pollution.

The International Dark Sky Society coined the term “light pollution” to define excessive or unnatural lighting at night. The term applies to any harmful effect of artificial light, including sky glare, glare, light penetration, light clutter, and energy waste. In addition, light pollution can affect astronomers, scientists, wildlife migrations and activity, and has been linked to human health concerns.

Migratory birds that use the moon and stars for navigation can be attracted by the light beams of tall buildings, towers, lighthouses, oil rigs, etc., causing disorientation and more accidents. In addition, nocturnal predators have the advantage of seeing over a larger area, and their prey must seek darkness and spend more time hiding and less in their daily activities.

A recent study published in the journal “Human-Wildlife Interactions” explains the effects of holiday lights on the environment during normal periods of darkness. Wildlife students at Texas A&M University-Kingsville report that holiday lights used to decorate the university’s campus were a source of seasonal light pollution, leading to higher predation rates by local eastern fox squirrels. Eastern fox squirrels exhibited normal day/night behavior throughout the year, but extended their foraging behavior to nearly four hours after sunset with the addition of holiday lights. The students documented a seven-fold increase in monthly squirrel mortality with the addition of holiday lights, likely due to the extended foraging season.

Additional research suggests that the public is often unaware that bright lights can negatively alter wildlife behavior. Therefore, they recommended educating students on how light pollution affects wildlife and the environment. Consider these suggestions:

* Check for a “Lights Out” program in your community. Some cities have adopted a program where interior and exterior lighting on tall buildings is dimmed or turned off during bird migration. Bare bulbs or upward-facing lights are replaced by hooded fixtures that shine only downward. If the lights cannot be turned off, a flat lens is used, as well as a reduced number and intensity of lights.

* Turn off unnecessary outdoor lights in the evenings, and turn off holiday lights at bedtime.

* Reduce light intensity by using fewer outdoor lights or using colored lights rather than pure white bulbs. Research shows that colored lights are less attractive to wildlife and can reduce negative effects on them.

* Consider your relationship with the environment and how your actions affect it.

* Consider cost, safety, health and environmental well-being decisions when planning and using outdoor lighting.

For the full research report, visit

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