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The sun sets behind the mountains as a herd of bison graze in Wind Cave National Park, August 14, 2001, in the southern Black Hills of South Dakota. David McNew/Getty Images

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11 unexplainable animal mysteries

Yes, one of them involves puppies.

Brian Resnick is Vox’s science and health editor, and is the co-creator of Unexplainable, Vox's podcast about unanswered questions in science. Previously, Brian was a reporter at Vox and at National Journal.

We share the planet with some 7.7 million species of animals. And every day, they confound us. Take the orcas (i.e., killer whales), for example, that have taken to ramming human vessels. Despite the tens of thousands of academic papers that have been written about them, the best any researcher can do to explain why they have been bludgeoning ships is shrug, and make some guesses.

Animals tease us by sharing the world with us, but by also withholding many of their secrets. “We don’t know what it’s like to conceive of the world as a killer whale or as a cat, or a nonhuman primate, or any individual that doesn’t have language really,” Jennifer Vonk, a cognitive scientist who studies animals at Oakland University, tells Vox’s Byrd Pinkerton.

On Unexplainable — Vox’s podcast that explores scientific mysteries, unanswered questions, and all the things we learn by diving into the unknown — we routinely return to stories about animals. The people who study them have enviable jobs: involving playing with puppies, or diving deep into the dark parts of the sea, or thinking through what the roar of a long-dead dinosaur might have sounded like.

And their works in turn provoke deep, fascinating questions. Questions about the interior lives of animals, but also about how humans are changing the world, about how wildlife is responding to those changes, and about how many forms of life depend on one another.

We might not be able to understand why animals do what they do. But we can at least understand how important these creatures are.

Here are 11 of the best questions about animal life we’ve encountered.

How did dogs evolve from wolves?

A close-up on a wolf’s face.
A young wolf stands in its enclosure at Eekholt Zoo in Germany.
Christian Charisius/picture alliance via Getty Images

Wolves and dogs are nearly genetically identical, sharing 99.9 percent of their DNA (and are more similar to each other than we are to our close animal relatives, like chimps). And, yet, they behave so differently. Wolves “still have all of their natural hunting behaviors which dogs don’t have,” Kathryn Lord, a scientist who studies the evolution of behavior, says on Unexplainable. “In the wolves, everything you greatly fear seeing in a dog pup is totally normal.”

Scientists still don’t know what precisely caused wolves and dogs to diverge from one another some 20,000 years ago. There are two main hypotheses. Either we humans domesticated wolves through a painstaking and dangerous process (possibly involving breastfeeding wolf pups!), or the wolves, essentially, domesticated themselves, by venturing closer and closer to our trash (i.e., food).

The answer is more than just trivia. “A better understanding of how this might have happened long ago might give us a better understanding also to how animals and plants and such today might be able to — or not able to — adapt to us,” Lord says.

And to find out, Lord has been playing with some puppies:

Further reading: How gray wolves divided America

Can animals feel grief?

An orca swimming.
An orca chases herrings on January 14, 2019, in the Reisafjorden fjord region, near the Norwegian northern city of Tromso in the Arctic Circle.
Olivier Morin/AFP via Getty Images

In 2018, a mother orca carried the carcass of her dead calf with herself for 17 days, covering thousands of miles of ocean. The journey inspired many media reports, but also, one big question: Was this mother orca grieving?

Similar stories have popped up across the animal kingdom: of a dog refusing to leave their deceased owner’s grave, of elephants apparently convening in “mourning,” of geese who appear to grieve the loss of a mate and refuse to eat.

Though it’s easy to look at these behaviors and assume these animals experience a human-like version of grief, the science of studying animal emotion and death behaviors is much trickier. Some scientists suggest it’s not possible to really know the interior life of an animal. Others say there’s a lot to be learned about the evolutionary history of grief if we go with the assumption that this is grief.

“There’s a principle in science of parsimony that was to say, you know, if something evolved in one species, it’s very unlikely that, you know, it didn’t also evolve in other species,” Jessica Pierce, a bioethicist, says.

On Unexplainable, Pierce and two other researchers help us think through this thorny question: What can we really learn from animal reactions to death?

Further reading: Breakups really suck, even if you’re a fish

What did dinosaurs sound like?

The skull of a dinosaur.
A life-size dinosaur model is seen on display at the California Academy of Sciences in San Francisco, California.
Tayfun Coskun/Anadolu Agency via Getty Images

What would it be like to be near a dinosaur? From fossil evidence, scientists can get a decent sense of what these ancient creatures looked like. But they still don’t know what they would have sounded like. Whereas hard tissues like bone can fossilize and leave us information about dinosaur stature and shape millions of years later, soft tissues — like the muscle and cartilage that help generate sound — do not fossilize as readily.

Many Hollywood depictions of dinosaur roars are not based in scientific reality (the T-Rex roar in Jurassic Park is partially based on an elephant. A mammal! Dinosaurs were reptiles!). So where do scientists start in trying to imagine realistic dinosaur noises? They look to dinosaurs’ closest relatives alive on Earth today.

Further reading: What did dinosaurs actually sound like? Take a listen.

Is there an insect apocalypse going on?

Butterflies, beetles, and moths pinned to a light blue background. Getty Images/Mint Images RF

Insect populations are shrinking all over the world, and entomologists are buzzing with questions. These scientists aren’t sure of the extent of the losses, or whether the trend is universally replicated around the globe. But what they have seen so far is concerning, given how integral insects are to our ecosystems.

“Scientists from many different countries across the world are coming to the same conclusion,” University of Florida entomologist Akito Kawahara tells Unexplainable’s Byrd Pinkerton.Insects are disappearing and they’re, and they’re disappearing pretty quickly. It is a really serious situation.”

Further reading: The loss of insects is an apocalypse worth worrying about

What’s living in our homes?

A woman vacuuming in an old-fashioned home.
Even “clean” homes have untold creatures living in them.
Corbis via Getty Images

In the 2010s, a team of scientists went into 50 homes around Raleigh, North Carolina. Their mission: to scour the homes, and find as many insect species as they could. And what they discovered was quite surprising (and a bit gross): The average house was home to around 100 species of insects. These weren’t “dirty” homes or ones located deep in the woods with the windows left open.

Instead, the findings illustrated that the typical human dwelling is an ecosystem for more creatures than we’ve realized. Which provokes another question: What are they doing in there? And what can we learn from them?

Further reading: The dozens of bug species that live in your home, in one chart

Can we find “missing” species?

The widemouth blindcat, a type of catfish, has been missing since the 1980s. If it’s not extinct, it can be found more than 1,000 feet below Earth in the Edwards Aquifer in south-central Texas.
Matthew Busch for Vox

As humans change the world and alter environments, more and more species are becoming “endangered” or “threatened” with extinction. But there’s another hugely important category that’s often overlooked: The species that slip through the cracks, and are classified as “missing.” Missing doesn’t mean extinct. It means scientists just haven’t documented a member of that species for a decade, or more.

“Missing” is an important designation. To conserve species, we need to know where they are. We can’t protect critters if we’re unsure if they still exist.

So scientists go out into the field, trying to find them, one by one:

Further reading: Why scientists are desperate to find a salamander that’s been missing for 71 years

Can a human really be friends with an octopus?

Close-up of a common octopus (Octopus vulgaris).
A. Martin UW Photography/Getty Images

In 2020, the documentary My Octopus Teacher provoked a fascinating question: Can a caring relationship form between humans and a sea creature such as an octopus? It’s not known whether the friendship in the documentary was genuine from the octopus’s perspective. The interior lives of animals may never be fully understood.

But it’s a fascinating question to think through. “It’s like interstellar travel,” science writer Ferris Jabr says on Unexplainable. “It’s like the closest we can come to that kind of alien contact moment.”

If we can connect with an octopus, what else could we connect with?

Further reading: Why do we care how smart animals are?

Why do so many sea creatures glow?

A ring of lights indicating the photophores of a jellyfish.
This image shows the bioluminescence of a jellyfish, as seen with the lights off.
NOAA’s National Ocean Service /Flickr

It’s wrong to say there’s no light in the depths of the ocean. There’s light, it just doesn’t come from the sun. Deep in the ocean (and also on the surface), divers find other-worldly displays of bioluminescence, sparkling like fireworks in the dark. Huge numbers of deep-water creatures light up in some way.

“There was just all of this flashing and glowing and sparkle all around me,” marine biologist Edie Widder recounts on Unexplainable about her undersea adventures. “You’re not viewing it at a distance. You’re in the center of the display. In fact, you’re part of it because any movement you make triggers flashes all around you.”

Widder has spent her career trying to figure out why so many marine creatures glow. The quest has led her to confront some of the weirdest, most elusive creatures on Earth.

Further reading: The underwater “eye” that is unlocking ocean secrets

What lives in the ocean’s mysterious “twilight zone”?

A graphic showing the layers of the ocean ranging from the sunlight zone near the surface through the twilight zone down to 1,000 meters and the midnight zone below that. Amanda Northrop/Vox

As you dive deeper into the ocean, less and less sunlight shines through. About 200 meters beneath the surface, you reach an area called the mesopelagic, or the “twilight zone.” Sunlight fades almost completely out of view, and our knowledge about these dark depths fades too.

“It’s almost easier to define it by what we don’t know than what we do know,” Andone Lavery, an acoustician at the Woods Hole Oceanographic Institution, told Vox’s Byrd Pinkerton. “It’s remote. It’s deep. It’s dark. It’s elusive. It’s temperamental.”

Yet this region of the ocean is extremely important. It’s possible — but not certain — that more fish are living in the twilight zone than the rest of the ocean combined, and these creatures of the dark ocean play a large role in regulating the climate.

Further reading: Scientists are probing the depths of the ocean’s Twilight Zone. So are commercial fisheries.

Why do whales beach themselves?

People surround a beached whale, pictured from above.
Rescuers help a sperm whale stranded on a beach on April 19, 2022, in Ningbo, Zhejiang Province of China.
Photo by VCG/VCG via Getty Images

Every year, thousands of marine mammals like whales end up trapped on beaches or in the shallow waters near shore. According to some studies, these strandings have been increasing.

But why do the animals do this? And are humans to blame?

It’s an incredibly difficult question to answer because while we know that humans are affecting the ocean environment, it can be hard to parse how those effects impact individual species.

But it’s important to figure it out. Enter Darlene Ketten, (a.k.a. “Dr. Doom”), a Woods Hole researcher who specializes in forensic investigations into whale deaths. She conducts Law and Order-type investigations into whale deaths. “What keeps us in the lab and on the beach is looking for more and more information,” Ketten says on Unexplainable, where she explains how she conducts her investigations.

Further reading: The curious case of the ancient whale bones

What will animals look like in the future?

An illustration of a dodo-like bird, a large praying mantis, and an aquatic rat. Amanda Northrop/Vox

It’s impossible to completely predict how evolution will play out in the future, but that doesn’t mean we can’t try. Reporter Mandy Nguyen asked biologists and other experts to weigh in: What would animals look like a million years from now?

The experts took the question seriously. “I do think it’s a really useful and important exercise,” told Nguyen. In thinking about the forces that will shape the future of life on Earth, we need to think about how humans are changing environments right now.

Further reading: The animals that may exist in a million years, imagined by biologists


10 ocean mysteries scientists haven’t solved yet


Astronomers spotted something perplexing near the beginning of time


How to catch a scientific fraud

View all stories in Unexplainable

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