Sunday, December 16, 2001		Nature

SNAKES are amazing creatures, they need not eat very often. Most of them require little more than their own weight each year and can fast for long periods. An Indian python was reported to have eaten nothing for 21 weeks and lost only 10 per cent of its body weight, while a reticulated python survived for a year and a half without a meal. But when they do eat, the quantity of food can be exceptionally large.

If we observe the creature minutely, we will find that all snakes have jaws that disarticulate, an adaptation to the fact that their body shape is basically long and narrow, and, without limbs or cutting teeth, they are not able to cut or break up food, instead, they swallow it whole. A large python might tackle prey the size of a wild pig or an antelope. It first catches the animal in its jaws then crushes it to death. It wraps its muscular body around the victim and slowly squeezes the life out of it. In reality, the snake cannot crush the bones, instead it prevents the prey from breathing. The entire process is a reflex action, the snake responding to the movements of its victims. When it is deemed to be dead, the snake loosens its hold and swallows the prey head first.

The problem of swallowing prey wider than itself has been solved by snakes in an ingenious way. The backward-pointing teeth prevent the prey from slipping away, and there are teeth both at top and at bottom. The six upper jaw bones are joined to the skull only by muscles and ligaments and can be moved independently of each other, and the two halves of the lower jaw are also not fused together. As the prey enters the mouth, the bones with teeth ‘walk’ the prey, moving alternately, first one side then the other. On reaching the oesophagus, the first section of the gut after the mouth, the snake contorts its neck into an S-shape and pushes the carcass down into the stomach. There is no shoulder (pectoral) girdle or breastbone (sternum) to restrict the passage and the ribs expand. The skin can be stretched considerably without ripping.

Life-and-death struggles are often reported when large, constricting snakes attempt to eat more than they bargained for, particularly crocodiles and alligators. The inevitable outcome, however, is a win for snake. A 23-foot-long African Rock python was killed by hunters and opened up only to reveal a five-feet-long Nile crocodile in its stomach. A 26-foot-long anaconda in eastern Brazil contained a similar-sized alligator. And a large Indian python was credited with eating a fully-grown leopard.

In zoos, constricting snakes have been seen to choke down the most extraordinary-sized meals. There is a tale told by a German zoo-keeper Carl Hagenback of a 20-foot-long reticulated python from Borneo being offered a 28-lb male goat and then a few hours later another 39-lb goat. Each was swallowed in about half an hour. A week later the zoo’s female rock goat died, the horns were cut off and the carcass, weighing 74-lb was offered to the same snake. It immediately grabbed it and began to swallow. Hagenback, thinking that this was an amazing feat, sent for a photographer, but the flash frightened the snake and it regurgitated the entire goat in less than half a minute.

For larger specimens, man can be on the snake’s menu. Reports in newspapers in November 1977 tell of the body of a 45-year-old man who was cut from the stomach of an 18-foot-long Indian python killed by villagers in Indonesia. The alarm was sounded when the villagers found the snake attacking a second person. And in July 1979, near Rocinha in Brazil, a fisherman was attending his nets when he was seized by an anaconda estimated to be 2 feet in diameter. A day later, the villagers found the remains of his body washed ashore. His chest had been crushed.

The egg-eating snake is equipped to crush not people but eggs; and it can deal with eggs twice the diameter of its body. Like all snakes, the egg-eating snake is able to disarticulate its jaws, but its mouth is wider, has smaller teeth and a larger gape, and is even more flexible than in other snakes. It can open its mouth to four times its resting size and swallow an egg whole.

At first, the egg is seized in the mouth, which, quite literally, stretches over the egg. Very slowly it moves down the gullet. The snake is still able to breathe for its windpipe can be pushed in and out of its mouth while feeding, the walls being strengthened with cartilage to prevent them from collapsing. The egg is broken in the gullet. Strong muscles in the neck contract and the spines on the neck vertebrae push down into the gullet and pierce the egg. The contents of the egg are digested while the egg shell is regurgitated.

This feature was published on December 9, 2001