In the pitch-black depths of Gabon’s Abanda cave system, something extraordinary is happening.
A population of dwarf crocodiles has abandoned the forest for a subterranean lifestyle, and the results are nothing short of astonishing.
These cave-dwelling reptiles are turning orange—yes, orange—from swimming in bat guano, and genetic research suggests they may be in the midst of evolving into an entirely new species right before our eyes.
Here’s what makes this discovery so remarkable: these crocodiles aren’t just surviving in the darkness—they’re thriving.
Scientists have found that these cave-dwelling reptiles are actually in better physical condition than their forest-dwelling counterparts, thanks to an abundant food supply and lack of predators.
It’s a perfect example of how isolation can drive evolutionary change in unexpectedly rapid timeframes.
The Accidental Discovery of Gabon’s Mutating Crocodiles
The story of these remarkable creatures began in 2010 when researchers first documented the presence of dwarf crocodiles (Osteolaemus tetraspis) living deep within the Abanda cave system in Gabon’s Ogooué-Maritime Province.
Until then, no one had studied these cave-dwelling reptiles, though local communities were likely aware of their existence.
A comprehensive study in 2016 revealed surprising differences between these cave crocodiles and their forest-dwelling relatives.
The most obvious distinction is their striking orange coloration—a stark contrast to the typical dark green or blackish hue of normal dwarf crocodiles.
“The unusual orange skin seen on adult crocodiles may be the result of their time swimming in bat guano, which is rich in urea,” explained Matthew Shirley, a conservation biologist from Florida International University who led the research.
Over time, this constant exposure appears to cause chemical bleaching of the crocodiles’ skin.
When Isolation Drives Evolution
Most people assume evolution takes millions of years, but the Abanda cave crocodiles challenge this notion.
These crocodiles appear to be evolving extraordinarily quickly by reptilian standards.
What’s particularly fascinating is that genetic analysis revealed one haplotype—a group of DNA variants inherited from a parent—found in the cave crocodiles that wasn’t present in their forest-dwelling cousins.
This genetic divergence suggests these crocodiles are becoming reproductively isolated.
“The [crocodiles in the] caves of Abanda stand out as an isolated genetic group,” noted study co-author Richard Oslisly, a researcher at France’s Institute of Research for Development.
“As a result of that isolation and the fact that few individuals come in or go out, they’re in the process of [becoming] a new species. Whether that happens soon or not is anyone’s guess.”
A Surprisingly Successful Strategy
You might think living in complete darkness would be challenging for crocodiles, but these reptiles have adapted remarkably well to their subterranean habitat.
The cave system provides a stable environment without seasonal fluctuations in temperature or precipitation, which can be advantageous for cold-blooded reptiles.
The cave crocodiles have transformed their diet entirely, feasting almost exclusively on cave crickets and bats that cling to the cave walls.
This specialized diet, combined with the absence of predators or competition, has resulted in these cave-dwelling crocodiles being in better condition than their forest counterparts.
Scientists believe the crocodiles maintain some connection to the outside world, particularly for reproduction.
The females likely lay their eggs near the cave entrances where some sunlight penetrates, allowing the eggs to incubate properly.
Once hatched, the juveniles venture deeper into the darkness, and as adults, they rarely leave the safety of the caves.
How Bat Poop Turns Crocodiles Orange
Perhaps the most visually striking aspect of these cave crocodiles is their unusual orange coloration.
This dramatic change isn’t genetic—at least not yet—but rather a chemical reaction.
The floors of the Abanda caves are covered in a thick layer of bat guano (feces), which creates a rich, nutrient-dense soup in which the crocodiles swim.
This guano contains high concentrations of urea, a nitrogen-rich compound.
Over time, prolonged exposure to this urea-rich environment appears to cause a chemical reaction that bleaches the crocodiles’ skin, turning it from dark green to bright orange.
This process is somewhat similar to how human hair can lighten when exposed to chlorine in swimming pools, but much more dramatic in its effects.
The orange coloration begins to appear as the crocodiles mature and spend more time in the guano-filled waters.
A Natural Laboratory for Evolution
Most evolutionary biologists can only study evolution retrospectively, examining fossils and genetic differences between species that diverged millions of years ago.
The Abanda cave crocodiles offer something extraordinarily rare: the opportunity to witness speciation—the process of a new species forming—in action.
“We’re witnessing a fascinating natural experiment,” Shirley explained.
“These crocodiles entered the caves at some point in the past—we don’t know exactly when, but it could be thousands of years ago—and have been adapting to this unique environment ever since.”
The genetic differences observed between the cave and forest populations suggest that the cave crocodiles are becoming reproductively isolated.
If this isolation continues, they may eventually become incapable of successfully breeding with their forest relatives—the textbook definition of speciation.
Unanswered Questions and Future Research
Despite the groundbreaking discoveries, many questions about these unique crocodiles remain unanswered.
How many of these orange crocodiles live in the cave system? How long have they been there?
How do they navigate in complete darkness? And most importantly, how far along are they in the speciation process?
Future research will focus on answering these questions and documenting the evolutionary changes as they occur.
Scientists hope to conduct long-term monitoring of the cave population to track changes in their genetics, morphology, and behavior over time.
“We’re dealing with a living laboratory,” Oslisly noted. “These crocodiles are giving us unprecedented insight into how a new species can form in isolation.”
Conservation Implications
While the discovery of these mutating crocodiles is exciting from a scientific perspective, it also raises important conservation concerns.
Dwarf crocodiles are already classified as vulnerable by the International Union for Conservation of Nature (IUCN), and this unique cave population represents a potentially important genetic lineage.
The Abanda cave system is located in a remote area, which has helped protect these crocodiles from human disturbance thus far.
However, as news of their existence spreads, there could be increased interest from tourism or scientific expeditions, which might disrupt their habitat if not properly managed.
The Gabonese government has expressed interest in protecting the cave system and its unique inhabitants, recognizing their scientific importance.
Conservation efforts will need to balance the need for research with the importance of preserving the isolation that has allowed these evolutionary changes to occur.
Nature’s Ability to Surprise
The discovery of orange, cave-dwelling crocodiles evolving into a new species reminds us that nature still has many secrets to reveal.
Even in the 21st century, when we might think we’ve cataloged most of Earth’s large animals, remarkable discoveries like this continue to emerge.
What makes the Abanda crocodiles particularly fascinating is that they represent an evolutionary journey that’s happening right now—not millions of years ago.
They’re living proof that evolution is an ongoing process, constantly reshaping life on our planet in response to environmental challenges and opportunities.
As Shirley puts it, “These crocodiles offer us a glimpse into the evolutionary process that’s usually hidden from view.
They’re a reminder that new species aren’t just something from the distant past—they’re being created right now, all around us.”
In the darkness of the Abanda caves, bathed in bat guano and turning inexplicably orange, these crocodiles are writing a new chapter in the story of life on Earth—one that scientists are just beginning to understand.
