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Frogs Use Storm Drains for Better Mating Calls

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As humans take up ever more space and urbanize the untamed wilderness, the animals that call these places home have a tough choice to make: move on to someplace else or adapt to their new surroundings.

Staying put can be especially tricky for animals that rely on sound to communicate with each other and steer clear of danger. Brick walls and human-made noise can change the acoustic landscape and drown out their mating calls or mask the sounds of approaching predators. In Taiwan, plucky little frogs are making the most of things. Instead of letting human infrastructure get in their way, they’re putting it to use. 

In suburban and rural areas of Taiwan, it’s pretty easy to find open concrete drains alongside roads and foot paths. Their bottoms are often caked in mud and covered in plant litter. This makes them attractive to small animals as travelways, mating sites, and even living space. But the concrete walls can make conversation difficult by causing sounds to ricochet and echo. Animals listening for each other's calls “will hear not just the direct sound wave, but also reflected waves arriving at different times,” say a team of researchers at National Taiwan University in Taipei.

But there’s an upside to that, depending on who’s doing the talking. “In contrast, some signals (e.g., those with narrow frequency bandwidths) can potentially benefit from reverberations,” the researchers say in a new paper. “The reflected sound waves can make the signal higher in amplitude and longer.” Mientien tree frogs seem to have figured this out, and the males are often found perched in the drains letting out their high pitched mating calls to attract females. 

When the team compared the calls of the frogs in the drains with those that sat next to them on the ground, they found that the drain calls were louder and longer. The echoes caused by the concrete didn’t degrade the calls. Instead, the researchers say, the drains acted like “miniature urban canyons” and actually amplified the narrow-bandwidth calls.

While the researchers didn’t look at how female frogs responded to the calls in this study, they suspect that the drain-aided calls are just what they want to hear. Other research has shown that female frogs and other amphibians are more attracted to long, loud calls. 

Hanging out in drains isn’t all fun and frog flirting, though. It also presents some challenges. The first is that the shape of the drains and the shelter they provide attracts snakes that can hide in the muck and ambush unwary prey. Many of the frogs seem to get around this by perching on branches leaning against the drain walls so they’ve got a good view of their surroundings. 

Another problem is that the steep concrete walls can be difficult to maneuver. Mientien tree frog mating involves the female carrying the male away from his calling perch to a damp place to reproduce, and the females might have a hard time hauling the males out of the drain. Whether that leads a lot of females to abandon males in the drains without mating or even ignore drain callers in the first place remains to be seen. For now, at least, the drain-as-megaphone looks like a clever workaround for tree frogs looking for love. 

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Animals
10 Notable Gestation Periods in the Animal Kingdom
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The gestation periods of the animal kingdom are varied and fascinating. Some clock in at just a few weeks, making any human green with envy, while others can last more than a year. Here are 10 notable gestation times for animals around the globe. The lesson? Be thankful that you’re not a pregnant elephant.

1. ELEPHANTS: 640-660 DAYS

Elephants are pregnant for a long time. Like really, really long. At an average of 95 weeks, the gestation period is more than double the length of a human pregnancy, so it shouldn't come as a shock that female elephants don't often have more than four offspring during their lifetimes. Who has the time?

2. HIPPOS: 8 MONTHS

A photo of a mother hippo and her baby in Uganda

Yes, it takes less time to make a hippopotamus than it takes to make a human.

3. GIRAFFE: 14-15 MONTHS

Baby giraffes can weigh more than 150 pounds and can be around 6 feet tall. Another fascinating tidbit: giraffes give birth standing up, so it's pretty normal for a baby to fall 6 feet to the ground.

4. KILLER WHALE: 17 MONTHS

There’s a reason for the long wait: after that 17 months, Baby Shamu emerges weighing anywhere from 265 to 353 pounds and measuring about 8.5 feet long. Yikes.

5. OPOSSUM: 12-13 DAYS

A baby opossum wrapped up in a blanket

Blink and you'll miss it: This is the shortest gestation period of any mammal in North America. But since the lifespan of an opossum is only two to four years, it makes sense.

6. GERBILS: 25 DAYS

Hey, they get off pretty easy.

7. GORILLAS: 8.5 MONTHS

It's not a huge surprise that their gestational periods are pretty similar to ours, right?

8. BLACK BEAR: 220 DAYS

A pair of black bear cubs

Also less than a human. Interestingly, cubs might only be 6 to 8 inches in length at birth and are completely hairless. 

9. PORCUPINE: 112 DAYS

This is the longest gestation period of any rodent. Thankfully for the mother, porcupine babies (a.k.a. porcupettes) are actually born with soft quills, and it's not until after birth that they harden up.

10. WALRUS: 15 MONTHS

Baby walruses? Kind of adorable. They certainly take their sweet time coming out, though.

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Goldfish Can Get Depressed, Too
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Don’t believe what Pixar is trying to sell you: Fish are not exactly brimming with personality. In aquariums, they tend to swim in circles, sucking up fragments of food and ducking around miniature treasure chests. To a layperson, fish don’t appear to possess concepts of happy, or sad, or anything in between—they just seem to exist.

This, researchers say, is not quite accurate. Speaking with The New York Times, Julian Pittman, a professor at the Department of Biological and Environmental Sciences at Troy University, says that fish not only suffer from depression, they can be easily diagnosed. Zebrafish dropped into a new tank who linger at the bottom are probably sad; those who enthusiastically explore the upper half are not.

In Pittman’s studies, fish depression can be induced by getting them “drunk” on ethanol, then cutting off the supply, resulting in withdrawal. These fish mope around the tank floor until they’re given antidepressants, at which point they begin happily swimming near the surface again.

It’s impossible to correlate fish depression with that of a human, but Pittman believes the symptoms in fish—losing interest in exploring and eating—makes them viable candidates for exploring neuroscience and perhaps drawing conclusions that will be beneficial in the land-dwelling population.

In the meantime, you can help ward off fish blues by keeping them busy—having obstacles to swim through and intriguing areas of a tank to explore. Just like humans, staying active and engaged can boost their mental health.

[h/t The New York Times]

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