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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Whale Sharks Can Live for More Than a Century, Study Finds
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Some whale sharks alive today have been swimming around since the Gilded Age. The animals—the largest fish in the ocean—can live as long as 130 years, according to a new study in the journal Marine and Freshwater Research. To give you an idea of how long that is, in 1888, Grover Cleveland was finishing up his first presidential term, Thomas Edison had just started selling his first light bulbs, and the U.S. only had 38 states.

To determine whale sharks' longevity, researchers from the Nova Southeastern University in Florida and the Maldives Whale Shark Research Program tracked male sharks around South Ari Atoll in the Maldives over the course of 10 years, calculating their sizes as they came back to the area over and over again. The scientists identified sharks that returned to the atoll every few years by their distinctive spot patterns, estimating their body lengths with lasers, tape, and visually to try to get the most accurate idea of their sizes.

Using these measurements and data on whale shark growth patterns, the researchers were able to determine that male whale sharks tend to reach maturity around 25 years old and live until they’re about 130 years old. During those decades, they reach an average length of 61.7 feet—about as long as a bowling lane.

While whale sharks are known as gentle giants, they’re difficult to study, and scientists still don’t know a ton about them. They’re considered endangered, making any information we can gather about them important. And this is the first time scientists have been able to accurately measure live, swimming whale sharks.

“Up to now, such aging and growth research has required obtaining vertebrae from dead whale sharks and counting growth rings, analogous to counting tree rings, to determine age,” first author Cameron Perry said in a press statement. ”Our work shows that we can obtain age and growth information without relying on dead sharks captured in fisheries. That is a big deal.”

Though whale sharks appear to be quite long-lived, their lifespan is short compared to the Greenland shark's—in 2016, researchers reported they may live for 400 years. 

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Animal Welfare Groups Are Building a Database of Every Cat in Washington, D.C.
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There are a lot of cats in Washington, D.C. They live in parks, backyards, side streets, and people's homes. Exactly how many there are is the question a new conservation project wants to answer. DC Cat Count, a collaboration between Humane Rescue Alliance, the Humane Society, PetSmart Charities, and the Smithsonian Conservation Biology Institute, aims to tally every cat in the city—even house pets, The New York Times reports.

Cities tend to support thriving feral cat populations, and that's a problem for animal conservationists. If a feline is born and grows up without human contact, it will never be a suitable house cat. The only options animal control officials have are to euthanize strays or trap and sterilize them, and release them back where they were found. If neither action is taken, it's the smaller animals that belong in the wild who suffer. Cats are invasive predators, and each year they kill billions of birds in the U.S. alone.

Before animal welfare experts and wildlife scientists can tackle this problem, they need to understand how big it is. Over the next three years, DC Cat Count will use various methods to track D.C.'s cats and build a feline database for the city. Sixty outdoor camera traps will capture images of passing cats, relying on infrared technology to sense them most of the time.

Citizens are being asked to help as well. An app is currently being developed that will allow users to snap photos of any cats they see, including their own pets. The team also plans to study the different ways these cats interact with their environments, like how much time pets spend indoors versus outdoors, for example. The initiative has a $1.5 million budget to spend on collecting data.

By the end of the project, the team hopes to have the tools both conservationists and animal welfare groups need to better control the local cat population.

Lisa LaFontaine, president and CEO of the Humane Rescue Alliance, said in a statement, “The reality is that those in the fields of welfare, ecology, conservation, and sheltering have a common long-term goal of fewer free-roaming cats on the landscape. This joint effort will provide scientific management programs to help achieve that goal, locally and nationally."

[h/t The New York Times]

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