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Howler Monkeys Can Either Be Really Loud or Well-Endowed

Dating is tough. We all know that. To attract the right mate, or any mate at all, you have to stand out from the crowd. Maybe your best quality is your sense of humor, or your twinkling eyes, or your sweet dance moves. Maybe—if you’re a howler monkey—it’s your enormous testicles, or your ability to yell louder than anyone else.

To ensure the continuation of their genes, male howler monkeys invest energy in making noise or making sperm. But scientists say they can’t do both. New analysis from the University of Cambridge finds that for howler monkeys, louder calls equal smaller balls.

The howler monkey is a curious creature, a terrier-sized primate with a tiger-sized roar. The monkeys can only reach about 15 pounds, but their calls are among the loudest on the planet. The males’ bellowing, belching calls serve two purposes: to catch lady monkeys’ attention, and to tell other males to take a hike.

The howler monkeys’ larger-than-life noises are possible thanks to a specialized bone called a hyoid. This hollow, pouch-shaped bone acts as an echo chamber, amplifying the calls before they ever leave the monkey’s mouth. The bigger the hyoid bone, the more noise a monkey can make.

This is more important for some species than others, and it all comes down to sex. Some howler monkeys have harem-type setups, where one male monkey mates with several female monkeys. In those arrangements, the challenge lies in appealing to the ladies and keeping other dudes away, but once mating has taken place, a male monkey can be pretty sure his sperm are safe.

Other species have a more relaxed sex scene in which female monkeys are free to take as many mates as they want. For these species, the males with the biggest cojones—and thus the most sperm—are the ones most likely to succeed in making monkey babies.

But yelling and making sperm each require a lot of energy. The monkeys can’t have their yelling and big balls, too.

These are the conclusions of a new paper published this week in the journal Current Biology. Researchers used 3-D laser scans to measure the hyoid bones and testes of 10 species. They found a distinct inverse relationship between the two. Harem-type species had larger hyoid bones and smaller testes, and the reverse was true for the free-love-type species. Exactly how this trade-off happened is not totally clear, lead author Jacob Dunn said in a press release.

“In evolutionary terms,” Dunn said, “all males strive to have as many offspring as they can, but when it comes to reproduction you can’t have everything.”

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Courtesy of The National Aviary
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Animals
Watch This Live Stream to See Two Rare Penguin Chicks Hatch From Their Eggs
Courtesy of The National Aviary
Courtesy of The National Aviary

Bringing an African penguin chick into the world is an involved process, with both penguin parents taking turns incubating the egg. Now, over a month since they were laid, two penguin eggs at the National Aviary in Pittsburgh, Pennsylvania are ready to hatch. As Gizmodo reports, the baby birds will make their grand debut live for the world to see on the zoo's website.

The live stream follows couple Sidney and Bette in their nest, waiting for their young to emerge. The first egg was laid November 7 and is expected to hatch between December 14 and 18. The second, laid November 11, should hatch between December 18 and 22.

"We are thrilled to give the public this inside view of the arrival of these rare chicks," National Aviary executive director Cheryl Tracy said in a statement. "This is an important opportunity to raise awareness of a critically endangered species that is in rapid decline in the wild, and to learn about the work that the National Aviary is doing to care for and propagate African penguins."

African penguins are endangered, with less than 25,000 pairs left in the wild today. The National Aviary, the only independent indoor nonprofit aviary in the U.S., works to conserve threatened populations and raise awareness of them with bird breeding programs and educational campaigns.

After Sidney and Bette's new chicks are born, they will care for them in the nest for their first three weeks of life. The two penguins are parenting pros at this point: The monogamous couple has already hatched and raised three sets of chicks together.

[h/t Gizmodo]

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holidays
Bleat Along to Classic Holiday Tunes With This Goat Christmas Album
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iStock

Feeling a little Grinchy this month? The Sweden branch of ActionAid, an international charity dedicated to fighting global poverty, wants to goat—errr ... goad—you into the Christmas spirit with their animal-focused holiday album: All I Want for Christmas is a Goat.

Fittingly, it features the shriek-filled vocal stylings of a group of festive farm animals bleating out classics like “Jingle Bells,” “Rudolph the Red-Nosed Reindeer,” and “O Come All Ye Faithful.” The recording may sound like a silly novelty release, but there's a serious cause behind it: It’s intended to remind listeners how the animals benefit impoverished communities. Goats can live in arid nations that are too dry for farming, and they provide their owners with milk and wool. In fact, the only thing they can't seem to do is, well, sing. 

You can purchase All I Want for Christmas is a Goat on iTunes and Spotify, or listen to a few songs from its eight-track selection below.

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