Scientists study ‘orange’ crocs
Stuck underground and exposed to urea in bat guano their skins change hue.
Gabon in West Africa is famous for its biodiversity, but in a galaxy of spectacular finds, one stands out: orange crocodiles. Scientists stumbled upon the unusual reptiles a decade ago in the gloom of isolated caves in the southern Omboue region. “When I approached with the torch in the cave, I saw red eyes ... crocodiles!” said geo-archaeologist Richard Oslisly. Two years later they hauled one out into the light and realised it was orange. “At first we thought the colour came from their food, because we saw that these reptiles ate orange bats.”
The scientists discarded other theories before speculating that lack of light in the Abanda caves may have caused depigmentation and urea in bat droppings may then have induced an orange hue. Under this theory, “the bat guano began to attack their skin and transformed their colour”, said speleologist Olivier Testa, a member of the research team.
Dwarf crocodiles are a well-studied species, but those in the cave complex stand out in the way they have adapted to their habitat. Oslisly, Testa and US researcher Matthew Shirley have carried out multiple expeditions to study the reptiles, which can grow to 1.7m. “We think these ... crocodiles have been in the Abanda caves for around 3 000 years, which correlates fairly well with a time when the sea level fell and this coastal zone became terrestrial once again,” Shirley said.
Mapping the cave complex, the scientists found four orange specimens out of 40. The “normal” colour crocodiles live in grottos connected to the surface. But the orange ones live in caverns accessible today only from vertical shafts. However, the cave system has smaller horizontal connections. One possibility is that the orange crocodiles entered their present habitat through narrow openings which they outgrew and could not return, and their skin eventually changed colour in response to the bat guano.
Oslisly wants the site to become a wholly protected sanctuary as “there’s much more to learn”, he said, pledging to develop the site for “scientific tourism”. – AFP