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Why Is Your Cat Such a Picky Eater? Blame Bitter Taste Receptors

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Cats are notoriously picky eaters—and one reason may be that they’re fine-tuned to detect bitterness. Cats can’t taste sweetness, but they have a dozen genes that code for bitter taste receptors. A recent study from researchers at the Monell Chemical Senses Center in Philadelphia and Cincinnati Children’s Hospital finds that at least seven of these bitter taste receptors are functional, indicating that cats are very sensitive to those tastes.

In order to figure out whether the 12 known bitterness receptor genes actually cause cats to taste bitterness, the researchers inserted these genes into human cells and figured out which ones responded to chemicals that cause people to taste bitterness (since cats can’t tell us when something is bitter). 

Scientists theorize that animals evolved to taste bitterness as a way to avoid poisons, especially in plants. However, cats are carnivores, and they wouldn’t be exposed to much bitterness in the course of their meat-eating meals, compared to a species that survives off plants. By that hypothesis, cats should have fewer bitter taste receptors than herbivores, since they don’t need them as much. 

So why do carnivorous cats still carry so many bitterness-tasting genes? It might help them avoid bitter compounds in animal products, like bile acids and venom. Or it might be that bitter receptors have functions beyond the mouth—for instance, one taste receptor in the human respiratory system has been found to ward off infection.

More research is needed to determine why exactly cats have such a fine-tuned palate for bitter foods, but in the meantime, the same technique that allowed the researchers to tell what cats seem to taste as bitter could help cat food makers find more delicious blends for picky kitties.

[h/t: Quartz]

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Animals
Where Do Birds Get Their Songs?
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Birds display some of the most impressive vocal abilities in the animal kingdom. They can be heard across great distances, mimic human speech, and even sing using distinct dialects and syntax. The most complex songs take some practice to learn, but as TED-Ed explains, the urge to sing is woven into songbirds' DNA.

Like humans, baby birds learn to communicate from their parents. Adult zebra finches will even speak in the equivalent of "baby talk" when teaching chicks their songs. After hearing the same expressions repeated so many times and trying them out firsthand, the offspring are able to use the same songs as adults.

But nurture isn't the only factor driving this behavior. Even when they grow up without any parents teaching them how to vocalize, birds will start singing on their own. These innate songs are less refined than the ones that are taught, but when they're passed down through multiple generations and shaped over time, they start to sound similar to the learned songs sung by other members of their species.

This suggests that the drive to sing as well as the specific structures of the songs themselves have been ingrained in the animals' genetic code by evolution. You can watch the full story from TED-Ed below, then head over here for a sample of the diverse songs produced by birds.

[h/t TED-Ed]

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Animals
Watch the First-Ever Footage of a Baby Dumbo Octopus
NOAA, Wikimedia Commons // Public Domain
NOAA, Wikimedia Commons // Public Domain

Dumbo octopuses are named for the elephant-ear-like fins they use to navigate the deep sea, but until recently, when and how they developed those floppy appendages were a mystery. Now, for the first time, researchers have caught a newborn Dumbo octopus on tape. As reported in the journal Current Biology, they discovered that the creatures are equipped with the fins from the moment they hatch.

Study co-author Tim Shank, a researcher at the Woods Hole Oceanographic Institution in Massachusetts, spotted the octopus in 2005. During a research expedition in the North Atlantic, one of the remotely operated vehicles he was working with collected several coral branches with something strange attached to them. It looked like a bunch of sandy-colored golf balls at first, but then he realized it was an egg sac.

He and his fellow researchers eventually classified the hatchling that emerged as a member of the genus Grimpoteuthis. In other words, it was a Dumbo octopus, though they couldn't determine the exact species. But you wouldn't need a biology degree to spot its resemblance to Disney's famous elephant, as you can see in the video below.

The octopus hatched with a set of functional fins that allowed it to swim around and hunt right away, and an MRI scan revealed fully-developed internal organs and a complex nervous system. As the researchers wrote in their study, Dumbo octopuses enter the world as "competent juveniles" ready to jump straight into adult life.

Grimpoteuthis spends its life in the deep ocean, which makes it difficult to study. Scientists hope the newly-reported findings will make it easier to identify Grimpoteuthis eggs and hatchlings for future research.

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