New research on the behavior of lizards found that the animals fled less frequently when humans wore dark blue clothing rather than the color red.
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Published on 8/9/2017 at 2:10 PM
A frightening encounter with police in Orange County inspired new research that determined clothing color may have a profound effect on animals.
Breanna Putnam of the University of California, Los Angeles, and the Natural History Museum of Los Angeles often studies the impacts of nonnative species on the environment. The research requires Putnam and her colleagues to wander neighborhoods and industrial parks catching anoles or other lizards by day and geckos by night.
“Especially while searching the walls of buildings with flashlights at night, people sometimes mistake us for criminals,” Putnam said.
And that is exactly what happened one night as she and a research advisor spotted geckos hanging out at an abandoned auto dealership. Two Orange County sheriffs saw what they thought were thieves, rounded a corner with guns drawn, and pointed them directly at Putnam’s adviser.
“With a bag full of geckos already in hand, it was pretty easy for him to convince them we were biologists, but it was clear that we needed to do something to make ourselves more conspicuous and more official,” Putnam said.
She and her team designed bright orange Urban Nature Research Center “Don’t Shoot Me” shirts in the hope that people would understand their mission and be more inclined to talk with them before jumping to conclusions. The researchers, however, suspected that their t-shirts would make them more conspicuous to lizards, which got them wondering whether or not clothing color could impact the results of their studies.
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Putnam looked at previously published research and found that some determined several species of birds with orange or red body patches are more tolerant of people wearing orange or red clothing.
In separate work, Nancy Burley of the University of California, Irvine, noticed that the colored bands she used to individually identify her zebra finches affected their preference in sexual partners, thereby messing up her research on mate choice in birds. The birds seemed to prefer pink, red, and black bands and were repelled by green and blue.
Burley theorized that birds were attracted to their own body colors and especially if they were colors tied to mate choice. She developed what is known as the “species-confidence hypothesis,” which argues the animals are “confident” that the potential mate is of the same species, helping them avoid hybridization.
Putnam decided to test this hypothesis out on western fence lizards (Sceloporus occidentalis). Males, nicknamed “blue bellies,” visually communicate with blue patches on the abdomen and throat.
Putman wore t-shirts of different colors — dark blue, light blue, red, and gray — and measured how close she could approach lizards before they fled. After they fled, she determined how easy they were to catch. She approached lizards that were already accustomed to the presence of humans, as well as lizards that had little experience with humans in their protected nature reserve.
She and her team completed 30 trials for each t-shirt color and used high-tech equipment to measure the conspicuousness of the t-shirts in the environment. Regardless of the lizard's previous interactions with humans, the study found that western fence lizards are preferentially biased toward dark blue, supporting the species confidence hypothesis.
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Lizards fled at shorter distances when Putman wore dark blue than when she wore red, according to the study, published in the journal PLOS ONE. She also captured lizards about twice as often when wearing dark blue than when wearing red. Because the pattern by which lizards fled from different colored t-shirts does not associate with the shirt’s conspicuousness, this suggests that the lizards responded to color and not detectability.
“Our main finding is that what you wear can influence how close you can approach an animal before it flees,” Putnam said. “This could have implications for ecotourism if people want to get close to wild animals to take pictures, and, as we also show, this could impact research outcomes if animals are hard to find and catch.”
Research on how humans perceive others based on clothing colors finds that the color red is especially noticed.
“Men actually find women more attractive when they are wearing red, even if they are just pictured near the color red,” Putnam said.
This could be because women’s cheeks naturally become redder, and lips become redder and more pronounced when they are near ovulation and approaching peak fertility. Even outside of such times, women may mimic such moments with rouge and lipstick, hoping to make themselves more attractive.
Oddly enough, red and yellow in nature frequently signal to predators that an animal is venomous, poisonous, or unpalatable, Putnam said. Think of the red hourglass marking on a black widow spider, or the bright yellows and reds of certain venomous snakes.
“But colors evolved for many different reasons,” Putnam said, adding that certain birds gravitate to red since it is a “sexualized” color for them, as it is for humans.
Lizards and other animals see the world somewhat differently than we do, however, as a result of their particular visual systems. Lizards, for example, have four retinal cones while humans have three. The fourth cone peaks in sensitivity in the ultraviolet range, allowing them to likely see UV wavelengths.
“We had to be careful not to wash our clothes with regular laundry detergent because they often contain brighteners (phosphors), which essentially enhance the UV-reflectance of clothes, making them appear brighter and clear to us,” Putnam said, adding that lizards would probably be sensitive to this UV effect.
The scent of laundry detergent, softeners, of bleach could also affect how an animal reacts to a person.
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While researchers are just beginning to understand the impact clothing has on animals, Putnam advises fieldworkers to wear the same clothes every time they conduct their studies on animals “so clothing color does not have a systematic effect,” she explained.
For others — even owners of skittish pets — she said, “You could do a test to determine whether you are able to get closer to an animal by wearing its specific body color or just a dull color. I’m sure the responses are going to be species-specific, so it is hard to make generalizations.”
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