Abanda Caves – caves of unique bat-eating crocodiles

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Crocodile in Abanda Caves
The unique crocodile of Abanda Caves / Abanda Expeditions / ©
Group of caves in the rainforest of eastern Gabon – Abanda Caves – has a very special secret. Here, in eternal darkness lives a group of crocodiles which seem to be turning into a new species.

History of discovery

First expedition

Gabon is quite rich with caves. Thus reports about some caves in the remote forests south from Ogooué was not a big surprise.
In a hope to find some archaeological material (which is very scarce here) in 2010 there was arranged an expedition organized by the French Institute of Research for the Development and led by archaeologist and geologist Richard Oslisly. Their path through the dense jungle was very hard but there was success – they found the caves. Explorers found 15 entrances, belonging to two cave systems named Mugumbi (400 m) and Dinguembou (350 m). In most cases the entrances were just pits – sinkholes to dark passages under the forest.
When the speleologist of the expedition Olivier Testa entered the caves, he was greeted by immense number frightened and loud bats, millions of insects and unbearable stench of bat guano. But there was something more – two big, glowing eyes were looking at him from the darkness.
To the surprise of researchers they found that in the caves below the forest live… crocodiles!

Further research

In the next expedition on August 2011 both cave systems were explorer further. One of the cave systems was approached only by a descent in 7 meters deep pit. Explorers found some 20 crocodiles.
In May 2015 took place the expedition. It was organized by the Association Hommes des Cavernes (France) and now led by Olivier Testa. New caves were discovered in this region as well as many discoveries about the local fauna. Of course, the unusual cave crocodiles were still lurking around.
Interesting and promising find from the 2015 expedition was a cave named Grottes des Minioptères (“Cave of bent-winged bats”) where the sediments and speleothemes (stalactites, stalagmites and similar cave formations) offer opportunity to explore the biological and climate history of this region.

Geology

Abanda caves have formed in a network of fissures in Cretaceous (Turonian) limestone and represent a group of pits which are interconnected with underground passages. If a creature happens to fall in some of these pits, it can not leave it, if it has no wings of good skills for climbing.

Crocodiles – hostages of caves?

Dwarf crocodiles

Comparison of common dwarf crocodile and Abanda Caves crocodile
Common dwarf crocodile and (orange) crocodile of Abanda Caves / Abanda Expeditions / ©
Crocodiles of Abanda Caves belong to the species of the smallest crocodiles in the world – dwarf crocodiles (Osteolaemus tetraspis). These reptiles live in the equatorial forests of West and Central Africa. In spite of the adjective “dwarf” this is not small creature – its length reaches 1.5 and even 1.9 m.

Genetic differences

These unique cave crocodiles definitely have genetic differences from the main species – they have lived in isolation for long time and are different both in their habits and their looks. The largest known cave crocodile is 1.7 m long – which is very large size for this species. These crocodiles have somewhat wider body, they have orange skin color. This unusual coloration might be caused by the permanent life in a water full with fermented bat guano (oh, appreciate your more or less clean bedlinen!).
Life of these creatures is not too sweet – they live in absolute darkness and are almost blind. Their diet is scarce and monotonous, consisting of occasional bats, numerous insects and algae.
Most likely these cave crocodiles are fast developing into a separate species.

Life in bat guano

Coming to these caves is very complex and it is not easy to find them in the vast rainforest. One has to look carefully and, surprisingly – to feel the smell, because the stench of bat guano is felt some distance from the caves. To the unaccustomed visitor stay in this place is unbearable.
Such is the realm of cave crocodiles – they live among more than 50,000 bats and millions of insects and numerous snakes. In fact there is a risk to get Ebola virus here – bats serve as a natural reservoir of this deadly pest. At the same time these caves are promising for biologists – here live also cave shrimps, fishes and other animals which might be rare of unique.
During the rain season caves are partly and even fully inundated. This might be the best time for crocodiles – they are actively swimming around and hunting.

Trap or deliberate exile?

It is possible that crocodiles are trapped in these caves for many thousands of years. Maybe in earlier times crocodiles could leave the caves, but, it seems, reptiles are not leaving these caves now.
Nevertheless life has shown its admirable ability to adapt: crocodiles live here and even have adapted well to this life. It is not known how large is their population – there definitely are more than 20 crocodiles and their number might reach even some hundreds.

References

  1. Scientific Expeditions Abanda, Gabon. Accessed on September 7, 2018
  2. Matthew H. Shirley, Brittany Burtner, Richard Oslisly, David Sebag, Olivier Testa. Diet and body condition of cave‐dwelling dwarf crocodiles (Osteolaemus tetraspis, Cope 1861) in Gabon. African Journal of Ecology, https://doi.org/10.1111/aje.12365. Accessed on September 7, 2018

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Abanda Caves - caves of unique bat-eating crocodiles -1.444192, 9.699241  The unique crocodile of Abanda Caves
Coordinates: 45.6656 N 13.9879 E (approximate)
Categories: Caves, Ecosystems
Values: Biology, Geology
Rating: (3.5 / 5)
Address: Africa, Gabon, Ogooué-Maritime province, in the rainforest east from Fernan Vaz Lagune
Name in French: Grottes d’Abanda
Length of caves: 850 m
Dominating species: dwarf crocodile (Osteolaemus tetraspis)

Landmarks of Gabon

Rainforest in Gabon
Rainforest in Gabon / Axel Rouvin, / CC BY 2.0
Gabon is sparsely populated country which per 85% is covered with equatorial rainforest. Highlights of this country are impressive ecosystems including unusual relict rainforest which persisted during the ice age thanks to the fog from cold ocean streams nearby. In the country are located also impressive waterfalls and rapids.

Caves

Entrance into Puerto Princesa Subterranean River, Philippines
Entrance into Puerto Princesa Subterranean River / , Flickr / CC BY 2.0
Every year there are reported exciting discoveries of new caves and discoveries of new qualities such as cave paintings in the ones known before. But there still is a feeling that our knowledge covers just a small part of all these monuments of nature.

Though, those which we know offer a surprising diversity of unusual features and impressive sights.

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