It's the stuff of nightmares: lost in a damp, dark cave with dozens of red glowing eyes staring back at you from the abyss.
If that description gives you the heebie-jeebies, then a recent expedition into the heart of Gabon’s crocodile-infested Abanda cave system probably wouldn't have been for you. The expedition was launched after researchers were tipped off about an unusual population of dwarf crocodiles that had apparently made the caves their home. And these weren't your average crocs. According to reports, they had bizarre, orange-colored skin, reports New Scientist.
Orange crocodilians are not the only frightening thing living in these African caves. The caves are also filled with the beating wings of bats everywhere, and cave crickets scurry about and make the walls seem alive. But it's in places like this where unexpected biological discoveries are often made.
“You walk in and there are just bats and crickets everywhere,” said the team’s crocodile expert, Matthew Shirley, from the Rare Species Conservatory Foundation. “The crocodiles are pretty good hunters anyway, but even if they didn’t have to pull bats off the walls, there are individuals falling to the floor all the time.”
It's not that unusual to encounter a crocodile in a cave in Gabon, but this is the first population documented taking up long-term residence in caves. A bountiful supply of bats means they never have to leave the caves for food; the cave crocs actually appear to be in better physical condition than their forest counterparts. What's really curious about the crocs, though, is their skin color. The deeper into the caves they go, the more orange they seem to become.
Initially, researchers wondered if the orange pigmentation meant that these crocodiles were in the process of adapting to a permanent cave lifestyle. The lack of light makes any kind of skin coloration needless, so most species of cave-evolved organisms lose their pigmentation entirely, often appearing ghostly white. In the case of the crocs, perhaps the orange color is transitional as they gradually become paler.
Shirley has an alternative, far more disgusting theory, though. He thinks the orange color comes from the fact that the cave crocs are constantly wading in an alkaline slurry formed from bat droppings.
“The urea in bat guano makes the water very basic,” he explained. “Eventually that will erode away the skin and change its color.”
So the diet of bats and crickets is doing wonders for the crocs' figures, but their complexions could use some work.
Though the crocs spend most of the year living in the caves, they still need to emerge from their caverns to breed. Crocodiles require big mounds of rotting vegetation to lay their eggs in, and nothing like that can be found in the cave system. So they still have a genetic connection to the outside world; they aren't evolving in complete isolation.
The research team found as many as 50 orange-tinted crocodiles living up to 100 meters into the cave system, but they suspect that's a short estimate for the entire population. An expedition deeper into the caves will be necessary for a full population assessment. That is, if anyone dares...