Reptiles
Dwarf Crocodile
Osteolaemus tetraspis · also called dwarf crocodile, African dwarf crocodile, bony crocodile, broad-snouted crocodile
The dwarf crocodile is the crocodilian that went small and armoured up. Rarely longer than a metre and a half, it is the tiniest of all the crocodiles and alligators, and the most completely encased in bone — plates even on its eyelids. It hunts crabs and frogs on the rainforest floor at night, and some of its populations live deep inside caves.
Overview
Dwarf crocodiles live in rainforest streams, swamps, and pools across West and Central Africa. They are heavy, dark, short-snouted, and usually 1–1.5 m — the smallest crocodilian in the world. They eat crabs, frogs, fish, snails, and insects, much of it caught by walking on land away from water on rainy nights.
Armour
On top of the usual crocodilian back plates, the dwarf crocodile has bony armour on its belly, neck, tail, and eyelids — more complete than any other crocodilian — likely a defence against leopards and pythons that could threaten a small croc.
Cave crocodiles
In Gabon’s Abanda caves, dwarf crocodiles live permanently inside flooded caves in total darkness, eating cave crickets and bats. Some are orange, their skin altered by guano-acidic water, and the isolated cave groups appear to be diverging genetically.
Status
The dwarf crocodile is Vulnerable and declining. Harmless and manageable in size, it is one of the most heavily hunted crocodilians for bushmeat across its range, and its forest-stream habitat is being logged, farmed, and mined.
Dwarf Crocodile: common questions
How small is the dwarf crocodile, and is it really the smallest crocodilian?
Yes, it is the smallest of the roughly two dozen living crocodilian species. Adults are usually between 1 and 1.5 metres long, and the largest reliable records are around 1.9 metres; most weigh 18 to 32 kilograms. By comparison, a large saltwater crocodile can exceed 6 metres and a tonne. The only real rival for "smallest crocodilian" is Cuvier's dwarf caiman of South America, which reaches a similar maximum length but is generally a little slimmer and lighter, so the African dwarf crocodile is usually given the title. Its small size is thought to be an adaptation to life in small rainforest streams and pools where a large crocodile could not manoeuvre or find enough food.
Why is the dwarf crocodile so heavily armoured?
A small crocodilian in a rainforest has predators that a six-metre crocodile does not — leopards, large pythons, big monitor lizards, and, for young animals, many more. The dwarf crocodile's response is armour. In addition to the bony plates that stiffen the back in all crocodilians, the dwarf crocodile has osteoderms reinforcing the belly, the sides of the neck, the tail, and even the eyelids, so that far more of the body is protected by bone. Combined with its habit of sheltering in burrows and hollow logs by day, this heavy plating makes it a difficult, low-reward target. The trade-off is extra weight and reduced flexibility, which is acceptable for a slow-moving ambush hunter that does not need to chase fast prey.
Are there really crocodiles living in caves?
Yes. In the Abanda cave system in Gabon, scientists have documented a substantial population of dwarf crocodiles living permanently inside flooded caves, some of them far from any entrance in total darkness. The cave crocodiles feed mainly on cave crickets and on bats, are trapped by the cave structure once they grow past a certain size (small ones can get in and out, large ones cannot), and many have an unusual orange coloration, thought to be caused by their skin being bleached and chemically altered by long immersion in water made acidic by bat guano. Genetic work suggests the cave population has been isolated long enough to be diverging from the surface dwarf crocodiles, making it a possible incipient new form. It is one of the few known cases of a crocodilian adapting to a cave environment.
Is the dwarf crocodile dangerous, and why is it threatened?
It is not dangerous to people in any practical sense — it is small, shy, secretive, mostly nocturnal, and its instinct is to flee or hide, and there are no records of dangerous attacks on humans. That very harmlessness, plus its manageable size, is part of why it is threatened. Across West and Central Africa the dwarf crocodile is one of the most frequently hunted crocodilians for bushmeat, caught by hand or with snares and traps and sold live or smoked in local and city markets, sometimes in large numbers. On top of this, the rainforest streams and swamps it needs are being logged, cleared for farming, polluted by mining, and drained. It is listed as Vulnerable and declining, and several regional populations are considered to be in serious trouble.