Timothy Knepp, U.S. Fish and Wildlife Service via Wikimedia Commons // Public Domain
Timothy Knepp, U.S. Fish and Wildlife Service via Wikimedia Commons // Public Domain

Scientists Say Light Colors Make Salmon More Belligerent

Timothy Knepp, U.S. Fish and Wildlife Service via Wikimedia Commons // Public Domain
Timothy Knepp, U.S. Fish and Wildlife Service via Wikimedia Commons // Public Domain

Marketers have long known the power of color to manipulate consumers. Red and yellow supposedly make us hungry, while blue can calm us down. Apparently, we’re not alone in our subconscious response to color; scientists say salmon kept in tanks with black backgrounds were four times less aggressive than those in light blue tanks. The findings were published last week in the journal PLOS ONE.

Fish consumption is on the rise, and a lot of that demand is met by a growing aquaculture (fish farming) industry. But even as consumers begin to demand beef and eggs from humanely raised cows and chickens, few have given fish welfare much thought.

Fortunately, scientists have. A large body of research indicates that fish are incredibly visual animals and are very sensitive to the appearance of their environments. Previous studies have shown that even the colors of gravel and light filtering through the water can affect fish health, fertility, and aggression. But nobody had considered the potential influence of background color until researchers from the University of British Columbia’s Animal Welfare Program decided to take a look.

The scientists brought in 100 Coho salmon (Oncorhynchus kisutch) and divided them into 10 tanks of 10 fish. Every day, each tank was lined with a piece of laminated paper divided into two different colors: either black with white, light gray, dark gray, or a pattern; and light blue with white, light gray, dark gray, or black. This way, the fish could swim to the side of the tank backed with the color they liked better. Each tank was equipped with a camera that filmed the salmon from above. Afterward, the researchers watched each tape and recorded how the fish behaved, as well as how many fish chose each color.

The salmon had very clear preferences. Time and time again, they opted to stay in front of the darkest background available. When they could have black, they chose black; in the absence of black, they settled for dark gray. And even when they weren’t on the darker side of the tank, just having a black or gray section in the tank seemed to soothe the fish.

The reverse was also true. Like Morticia Addams, the salmon seemed almost offended by pastels. When the fish were forced to endure light blue backgrounds they became four times more aggressive than they were in black-backed tanks, chasing, charging, and even biting their tank-mates.

Why does this matter? Well, guess what color is currently the default for salmon fishery tank backgrounds. Did you guess light blue? You’re right.

The researchers note that their study had some limitations. The fish they studied were all the same age, and a salmon’s aggressive tendencies do vary over its lifespan. They also didn’t test the effects of water temperature and season. Still, this is progress towards a better understanding.

“Fish both preferred and were dramatically less aggressive in darker backgrounds,” co-author Marina Keyserlink said in a press statement. “Thus, we found a relatively simple environmental modification that has the potential to improve animal welfare."

These Sparrows Have Been Singing the Same Songs for 1500 Years

Swamp sparrows are creatures of habit—so much so that they’ve been chirping out the same few tunes for more than 1500 years, Science magazine reports.

These findings, published in the journal Nature Communications, resulted from an analysis of the songs of 615 adult male swamp sparrows found in six different areas of the northeastern U.S. Researchers learned that young swamp sparrows pick up these songs from the adults around them and are able to mimic the notes with astounding accuracy.

Here’s what one of their songs sounds like:

“We were able to show that swamp sparrows very rarely make mistakes when they learn their songs, and they don't just learn songs at random; they pick up commoner songs rather than rarer songs,” Robert Lachlan, a biologist at London’s Queen Mary University and the study’s lead author, tells National Geographic.

Put differently, the birds don’t mimic every song their elders crank out. Instead, they memorize the ones they hear most often, and scientists say this form of “conformist bias” was previously thought to be a uniquely human behavior.

Using acoustic analysis software, researchers broke down each individual note of the sparrows’ songs—160 different syllables in total—and discovered that only 2 percent of sparrows deviated from the norm. They then used a statistical method to determine how the songs would have evolved over time. With recordings from 2009 and the 1970s, they were able to estimate that the oldest swamp sparrow songs date back 1537 years on average.

The swamp sparrow’s dedication to accuracy sets the species apart from other songbirds, according to researchers. “Among songbirds, it is clear that some species of birds learn precisely, such as swamp sparrows, while others rarely learn all parts of a demonstrator’s song precisely,” they write.

According to the Audubon Guide to North American Birds, swamp sparrows are similar to other sparrows, like the Lincoln’s sparrow, song sparrow, and chipping sparrow. They’re frequently found in marshes throughout the Northeast and Midwest, as well as much of Canada. They’re known for their piercing call notes and may respond to birders who make loud squeaking sounds in their habitat.

[h/t Science magazine]

ZUMA Press, Inc., Alamy
5 Fascinating Facts About Koko the Gorilla
ZUMA Press, Inc., Alamy
ZUMA Press, Inc., Alamy

After 46 years of learning, making new friends, and challenging ideas about language, Koko the gorilla died in her sleep at her home at the Gorilla Foundation in Woodside, California on June 21, 2018. Koko first gained recognition in the late 1970s for her ability to use sign language, but it was her friendly personality that made her a beloved icon. Here are five facts you should know about the history-making ape.


Francine "Penny" Patterson, then a graduate student at Stanford University, was looking for an animal subject for her inter-species animal communication experiment in the early 1970s when she found a baby gorilla at the San Francisco Zoo. Originally named Hanabiko (Japanese for "fireworks child," a reference to her Fourth of July birthdate), Koko took to signing quickly. Some of the first words Koko learned in "Gorilla Sign Language," Patterson's modified version of American Sign Language, were "food," "drink," and "more." She followed a similar trajectory as a human toddler, learning the bulk of her words between ages 2.5 and 4.5. Eventually Koko would come to know over 1000 signs and understand about 2000 words spoken to her in English. Though she never got a grasp on grammar or syntax, she was able to express complex ideas, like sadness when watching a sad movie and her desire to have a baby.


Not only did Koko use language to communicate—she also used it in a way that was once only thought possible in humans. Her caretakers have reported her signing about objects that weren't in the room, recalling memories, and even commenting on language itself. Her vocabulary was on par with that of a 3-year-old child.


Koko was the most famous great ape who knew sign language, but she wasn't alone. Michael, a male gorilla who lived with Koko at the Gorilla Foundation from 1976 until his death in 2000, learned over 500 signs with help from Koko and Patterson. He was even able to express the memory of his mother being killed by poachers when he was a baby. Other non-human primates have also shown they're capable of learning sign language, like Washoe the chimpanzee and Chantek the orangutan.


Koko received many visitors during her lifetime, including some celebrities. When Robin Williams came to her home in Woodside, California in 2001, the two bonded right away, with Williams tickling the gorilla and Koko trying on his glasses. But perhaps her most famous celebrity encounter came when Mr. Rogers paid her a visit in 1999. She immediately recognized him as the star of one of her favorite shows, Mister Rogers' Neighborhood, and greeted him by helping him take off his shoes like he did at the start of every episode.


Koko was never able to have offspring of her own, but she did adopt several cats. After asking for a kitten, she was allowed to pick one from a litter for her birthday in 1985. She named the gray-and-white cat "All Ball" and handled it gently as if it were her real baby, even trying to nurse it. She had recently received two new kittens for her 44th birthday named Ms. Gray and Ms. Black.


More from mental floss studios