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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."

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Slow Motion Is the Only Way to Appreciate a Chameleon’s Lightning-Fast Tongue
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From the unusual way they walk, to their ability to change color, the evolutionary adaptations of chameleons are pretty bizarre, and some of them remain mysterious even to scientists. Their super-powered tongues, for instance, can dart out so quickly that the movement can barely be seen with the naked eye. But modern high-speed cameras have enabled researchers at the University of South Dakota to observe this appendage at work like never before. The video below, shared over at The Kid Should See This, includes some of that groundbreaking footage, and it's pretty amazing to watch.

Shooting at 3000 frames per second, the camera was able to capture every split-second aspect of the chameleon's tongue strike. Slowed down, the video allows you to see how every component of the process works in harmony: First, muscles in the lizard’s tongue contract like the string of a bow. Then, when that tension is released, the bony base of the tongue shoots forward, pushing the sticky, elastic part toward the chameleon’s prey.

According to Christopher Anderson, one of the scientists who conducted the high-speed camera research, larger chameleons can catapult their tongues forward at distances of one to two times their body length. For smaller chameleons, this distance can reach up to two and a half times their body length. “Small chameleons need to be able to eat more food for their body size than large chameleons,” he tells bioGraphic in the video, “and so by being able to project their tongues proportionately further than these large species, they basically are opening up additional feeding opportunities to themselves that they wouldn’t have if they had a shorter tongue.”

To see one of nature’s greatest hunting tools in action, check out the full video below.

[h/t The Kid Should See This]

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There May Be an Ancient Reason Why Your Dog Eats Poop
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Dogs aren't known for their picky taste in food, but some pups go beyond the normal trash hunting and start rooting around in poop, whether it be their own or a friend's. Just why dogs exhibit this behavior is a scientific mystery. Only some dogs do it, and researchers aren't quite sure where the impulse comes from. But if your dog is a poop eater, it's nearly impossible to steer them away from their favorite feces.

A new study in the journal Veterinary Medicine and Science, spotted by The Washington Post, presents a new theory for what scientists call "canine conspecific coprophagy," or dogs eating dog poop.

In online surveys about domestic dogs' poop-eating habits completed by thousands of pet owners, the researchers found no link between eating poop and a dog's sex, house training, compulsive behavior, or the style of mothering they received as puppies. However, they did find one common link between the poop eaters. Most tended to eat only poop that was less than two days old. According to their data, 85 percent of poop-eaters only go for the fresh stuff.

That timeline is important because it tracks with the lifespan of parasites. And this led the researchers to the following hypothesis: that eating poop is a holdover behavior from domestic dogs' ancestors, who may have had a decent reason to tuck into their friends' poop.

Since their poop has a high chance of containing intestinal parasites, wolves poop far from their dens. But if a sick wolf doesn't quite make it out of the den in time, they might do their business too close to home. A healthier wolf might eat this poop, but the parasite eggs wouldn't have hatched within the first day or two of the feces being dropped. Thus, the healthy wolf would carry the risk of infection away from the den, depositing the eggs they had consumed away in their own, subsequent bowel movements at an appropriate distance before the eggs had the chance to hatch into larvae and transmit the parasite to the pack.

Domestic dogs may just be enacting this behavior instinctively—only for them, there isn't as much danger of them picking up a parasite at home. However, the theory isn't foolproof. The surveys also found that so-called "greedy eaters" were more likely to eat feces than dogs who aren't quite so intense about food. So yes, it could still be about a poop-loving palate.

But really, it's much more pleasant to think about the behavior as a parasite-protection measure than our best pals foraging for a delicious fecal snack. 

[h/t The Washington Post]

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