The cave lifestyle has impacted body condition and skin color in this dwarf crocodile population.
Crocodiles living in Gabon’s Abanda cave system are sampling the local cuisine. According to a study published in the African Journal of Ecology, cave-dwelling bats and crickets are on the menu for this first-ever documented population of cave-dwelling dwarf crocodiles.
The sheer abundance of tasty critters in the caves may have drawn the crocodiles — which normally reside in swamps and rainforest rivers — to this unusual habitat.
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“You walk in and there are just bats and crickets everywhere,” study lead author Matthew Shirley, from the Rare Species Conservatory Foundation in the US, tells New Scientist. “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.”
Compared to young crocodiles living in the surrounding forest, who mainly eat freshwater crustaceans and insects, those living in the cave were found to have superior body condition — likely due to the availability of their cave-dwelling prey.
Venturing further into the caves, the team of scientists was met with yet another surprise: some of the older male crocodiles were turning a bright shade of orange.
They wondered if the orange skin color represented a stage on the way to pigmentation loss — a process that commonly occurs in cave-dwelling animals, as skin color serves no function under pitch-dark conditions.
However, as Shirley notes, cave-dwelling crocodiles still emerge during the breeding season to lay eggs outside of the cave, so their skin color change probably isn’t an adaptation to low light.
Rather, he believes that the numerous bats in the cave, and their copious droppings, have been alkalizing the waters through which these crocodiles swim. “The urea in bat guano makes the water very basic,” Shirley says. “Eventually that will erode away the skin and change its colour.”
The team calls for further research into this “unique system” to better understand the evolutionary implications of cave use by dwarf crocodiles.
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