When the sun disappears behind Panama's mountains and the last birds begin settling into the trees, an entirely different world comes alive above your head.
A dark shape suddenly shoots between the trees. Another skims over a river. Somewhere above the canopy, a bat is using sound to locate prey that you cannot even see.
For many travelers, bats are simply those mysterious shadows flying around streetlights, hostels and balconies after dark.
But Panama has an extraordinary bat world.
More than 120 species of bats are found in the country, with an astonishing variety of sizes, appearances, diets and hunting techniques. On tiny Barro Colorado Island in the Panama Canal, researchers have recorded 76 different bat species.
And the differences between them can be incredible.
Some eat fruit.
Some drink nectar.
Others specialize in insects.
Some catch fish.
Some hunt frogs.
And yes, Panama is also home to vampire bats.
The Night Begins With Sound
Perhaps the most incredible thing about bats is the way they experience the world.
When a bat flies through the darkness of the jungle, it doesn't have to rely entirely on its eyes. Many species use echolocation.
They produce extremely high frequency sounds and listen to the echoes bouncing back from trees, insects, water and other objects.
Many of these sounds are completely inaudible to humans.
To a bat, however, the night is anything but empty.
The darkness is filled with information.
A tree isn't simply an obstacle. An insect isn't simply a tiny moving dot. Even the surface of a river can reveal information.
Some bats can detect tiny disturbances on the surface of the water caused by fish.
And then the hunt begins.
The Bat That Goes Fishing
One of Panama's most spectacular bats is the greater bulldog bat, sometimes known as the fishing bat.
This remarkable animal hunts over water.
It uses echolocation to detect movements made by fish near the surface. It then skims across the water and uses its large claws to grab its prey.
The bat can even carry captured fish in special cheek pouches while continuing to fly.
Think about that for a moment.
A bat flying through the darkness over a Panamanian river, detecting a fish with sound, dropping toward the water and grabbing it with its feet.
It sounds like something from a fantasy movie.
But in Panama, it is simply another night in the jungle.
Most Bats Aren't Vampires
Bats have a serious public relations problem.
For many people, the word "bat" immediately brings images of blood, caves and horror movies.
The reality is dramatically different.
The vast majority of Panama's bats don't drink blood at all.
Many eat fruit, nectar or insects. Some are important pollinators. Others spread seeds throughout the forest.
So when you see a bat flying through the jungle at night, it may not be hunting anything at all.
It could be helping plant the next generation of trees.
The Forest Gardeners of the Night
Fruit eating bats play an important role in tropical ecosystems.
A bat eats fruit and then flies somewhere else.
Eventually, the seeds pass through its digestive system and are deposited somewhere far from the original tree.
In this way, bats help plants spread throughout the forest.
In a tropical rainforest where hundreds of plant species compete for sunlight and space, these nocturnal seed dispersers can have a surprisingly important influence.
Some bats can also travel much farther than many smaller forest animals.
They aren't simply residents of the rainforest.
They are helping the rainforest regenerate.
Panama's Bats Are Incredibly Diverse
One of the most fascinating things about Panama's bats is that there really isn't such a thing as "the bat."
There are tiny species that look almost mouse-like.
Others have enormous wings.
Some have bizarre faces.
Others have remarkably long noses.
There are bats with enormous ears and others whose ears are barely noticeable.
And then there are species that look as though nature decided to ignore all the normal design rules.
One particularly fascinating example is the wrinkled-faced bat, a spectacular species found in Panama.
Its face is covered in unusual folds and wrinkles, giving it an almost prehistoric appearance. It feeds on fruit and has powerful jaws capable of dealing with hard seeds. Males also have a flap of skin that can cover part of their face.
Nature clearly has a sense of humor.
Discovering Bats That Science Didn't Know
Panama continues to surprise scientists.
Researchers working around Gamboa discovered a previously unrecognized species of dog-faced bat, now known as Freeman's dog-faced bat.
These bats fly high and fast, making them difficult to capture using traditional methods. Researchers eventually collected enough specimens to study their DNA and echolocation calls.
It is a remarkable reminder that even in one of the world's most heavily studied tropical environments, there are still secrets flying through the darkness.
You can stand in one of the most famous biological research regions in Central America and still encounter animals that science is only beginning to understand.
Barro Colorado Island: A Bat Paradise
In the middle of the Panama Canal lies Barro Colorado Island.
The island is famous among biologists because scientists have been studying its tropical forest for decades.
But for bat researchers, it is particularly extraordinary.
Seventy six bat species have been recorded on the relatively small island.
Think about that.
Dozens of different bat species sharing the same forest.
How do they avoid competing for exactly the same food?
The answer is fascinating.
One species hunts high above the canopy.
Another flies close to the forest floor.
Another specializes in open water.
One eats fruit.
Another catches insects.
Another searches among leaves.
Each species has its own ecological niche.
The night isn't an empty space.
It is an enormous ecosystem happening above the ground.
Panama's Jungle Changes Completely After Dark
Walking through a tropical forest during the day is already an incredible experience.
At night, the same forest becomes something completely different.
The birds disappear.
Frogs begin calling.
Insects fill the darkness with sound.
And above your head, the bats begin moving.
Some species fly high above the canopy.
Others stay close to tree trunks.
Some race across open spaces.
Others patrol rivers and streams.
For a backpacker who has spent the day exploring Panama, a night walk can reveal an entirely different side of the country.
You discover that the jungle never really sleeps.
It simply changes its residents.
The Vampire Bat
And then there is the animal responsible for almost all of the bad publicity surrounding bats.
The vampire bat.
Yes, Panama really does have vampire bats.
But the reality is far less dramatic than Hollywood suggests.
These bats feed on blood and have evolved specialized methods for finding suitable prey.
Their saliva contains compounds that interfere with blood clotting, which has made vampire bats particularly interesting to medical researchers studying blood clots and circulation.
So even the animal that many people find frightening may contain biological secrets that could eventually help humans.
Bats Are Eating Your Insects
Many of Panama's bats are insect eaters.
Every night they can remove enormous numbers of insects from the air.
Moths, beetles, mosquitoes and countless other nocturnal insects become part of the menu.
So if you're sitting outside a hostel at night and a bat suddenly flies over your head, there is a good chance it isn't interested in you at all.
It's interested in whatever is flying around you.
In other words, the bat is working.
Scientists Are Listening to the Night
Panama is one of the world's important locations for tropical bat research.
The Smithsonian Tropical Research Institute has conducted decades of research into bats and other wildlife.
Long term monitoring projects are particularly valuable because scientists can return to the same forests repeatedly and observe how bat populations change over time.
That information can help researchers understand how tropical ecosystems respond to changing rainfall, climate and forest conditions.
It may sound like quiet scientific work.
But in reality, scientists are listening to one of the most sensitive parts of the ecosystem.
When bats change, something else may be changing with them.
Where Can Backpackers See Bats in Panama?
You don't have to be a scientist to experience Panama's bats.
Forested areas with rivers, caves, mature trees and little artificial light are particularly interesting.
The areas around the Panama Canal are especially important for bat research, including Gamboa and Soberanía National Park.
But you can encounter bats throughout Panama's tropical forests, including the mountains of Chiriquí and the more remote regions of Darién.
And perhaps the best way to see them is incredibly simple.
Find somewhere quiet.
Sit down.
Wait for sunset.
Look up.
At first, you might see nothing.
Then suddenly there is one.
A dark shape crossing the last blue light of the evening.
It disappears.
Then another appears.
And another.
Before long, you realize the sky is full of life.
The Animals We Almost Never Notice
That may be the most fascinating thing about bats.
They are everywhere around us, yet we barely notice them.
During the day, many hide in trees, caves, cracks, foliage and other sheltered places.
At night, when most people are asleep, they emerge.
They fly above our heads.
They hunt beside us.
They pollinate flowers.
They spread seeds.
They eat insects.
They catch fish.
And some drink blood.
Yet most people only ever see a few seconds of their nocturnal lives.
Panama teaches you something important about the rainforest.
The jungle doesn't become empty when the sun goes down.
It becomes occupied by a completely different cast of characters.
And somewhere above the rainforest, while most travelers are sleeping, the world of bats is only just beginning.