Reptiles
Egg-eating Snake
Dasypeltis scabra · also called common egg-eating snake, rhombic egg eater
The African egg-eating snake is a specialist that has thrown away the standard snake toolkit. It has no functional teeth and no venom. Instead it swallows whole bird eggs far bigger than its head, cracks them open from the inside with spikes on its own backbone, drinks the contents, and neatly spits out the crushed shell.
Overview
The common egg-eating snake ranges across almost all of sub-Saharan Africa, wherever birds nest — savanna, grassland, bush, and dry forest. It is slender, small-headed, nocturnal, and a good climber, hunting bird nests in trees, shrubs, and on the ground. It eats nothing but eggs, ever.
Swallowing the impossible
The snake’s skull is built for extreme flexibility — loosely jointed, very mobile bones, elastic thinly scaled skin, and no teeth in the way. It works its mouth over an egg like a sock over a foot, and an egg two or three times wider than its head slides into the stretched throat.
Breaking in from the inside
Projecting from the underside of the snake’s neck vertebrae are 20–30 bony spurs. With the egg in its throat, the snake arches its spine so these saw into the shell, flexing until it collapses. It then squeezes the egg to force the contents into its stomach, compacts the shell into a tidy pellet, and regurgitates the husk.
All bluff
Harmless as it is, the egg-eater survives by impersonating a viper. Threatened, it coils into a jerky C-shape, inflates, and rasps its saw-edged scales together to hiss — closely mimicking the deadly saw-scaled viper it lives alongside, right down to matching colour patterns.
A seasonal life
Eggs are only available for a few months a year, so the snake gorges in the nesting season, storing fat, and then fasts for six months or more.
Status
Dasypeltis scabra is Least Concern, common and widespread.
Egg-eating Snake: common questions
How can a thin snake swallow an egg wider than its own head?
The African egg-eating snake has an extraordinarily flexible skull and jaw. Like other snakes it can disconnect its lower jawbones at the front, but it takes this further — the bones of the snout and jaw are loosely joined and very mobile, the skin of the head and neck is elastic and only thinly scaled, and there are no big teeth in the way. The snake works its mouth over the egg like a sock over a foot, "walking" its jaws forward in alternating movements, and the egg passes into the stretched throat. A snake the thickness of a pencil can engulf an egg two or three times the diameter of its head.
How does it break the shell without teeth?
Once the egg is in the throat, the snake arches its neck and body so that a set of bony spikes on the underside of its neck vertebrae — projections of the bones themselves, sometimes called vertebral or "gular" teeth — press down into the shell. By flexing repeatedly it saws these spurs through the shell until it cracks and collapses. Then the snake contracts its body muscles to squeeze the egg, forcing the yolk and white down into the stomach, and finally compacts the crushed shell into a tight pellet and brings it back up through its mouth. The whole process, from starting to swallow to spitting out the husk, can take twenty minutes to over an hour.
Is the egg-eating snake dangerous?
No — it is completely harmless. It has no venom and effectively no teeth, so it cannot bite in any meaningful way. Its defence is entirely bluff — it coils into a tight, jerky C-shape, inflates and flattens its body, and rubs its saw-edged scales together to produce a loud rasping hiss, closely imitating the display of the highly venomous saw-scaled viper that shares its range. Many of its colour forms also resemble local vipers. A predator that has learned to avoid saw-scaled vipers avoids the egg-eater too.
How does it survive if it only eats eggs?
With difficulty, and by fasting. Bird eggs are only available for a few months of the year in any given area, during the nesting season, so an egg-eating snake gorges heavily when eggs are plentiful — eating far more than its body weight in a season and storing the energy as fat — and then goes without food for the remaining six or more months. Females may skip breeding in a poor year. This tight dependence on a seasonal, patchy food supply is why the snake stays small and why it has such a wide but thin distribution.