Update: A snake with real bite

One characteristic of snakes is that they are supposed to swallow their meals whole. But scientists have discovered one species of serpent that manages to take bites out of its unfortunate prey. The particular snake, which lives in Singapore, feeds on soft-bellied crabs by tearing them apart one bite at a time. Usually snakes open their dislocated jaws wide enough to swallow whatever they can fit inside their mouths.

One characteristic of snakes is that they are supposed to swallow their meals whole. But scientists have discovered one species of serpent that manages to take bites out of its unfortunate prey. The particular snake, which lives in Singapore, feeds on soft-bellied crabs by tearing them apart one bite at a time. Usually snakes open their dislocated jaws wide enough to swallow whatever they can fit inside their mouths.

Bruce Jayne of the University of Cincinnati, Harold Vordis of the Field Museum of Natural History and Peter Ng of the National University of Singapore, found that this particular species of crab-eating snake, Gerarda prevostiana (pictured), used a different tactic. The snake itself forms a loop around its prey, holding it tightly while it tears off limbs and anything else that comes loose.

"The snake literally rips the crab's body apart. They'll tug and pull on it to tear it apart," said Jayne.

The ability to take bite-sized chunks off crabs is unusual given that the teeth of snakes are not designed for slicing or cutting. Instead, they curve back into the mouth, which is a better design for holding prey tightly so they don't escape. The advantage to the snake that manages to overcome this dental limitation is that it can eat bigger prey and grow bigger as a result. The research findings are published in this week's issue of Nature magazine.

¿ West Africa has seen its fishing stocks collapse by 80 per in recent years and this once-rich source of marine life is almost as depleted as the fishing grounds of the North Atlantic. Some experts are predicting that the coast off West Africa will become like the Grand Banks off Newfoundland, which a decade or so ago had the richest cod fishing in the world, but is now practically dead.

According to New Scientist, the depletion coincides with a deal struck with the European Union, which is allowing European fishing vessels to take more fish than ever before off the coast of Angola, with similar deals in the pipeline for Senegal and Mauritania.

"Fisheries in West Africa will go the way of the Grand Banks if something doesn't change," Daniel Paulty of the University of British Columbia told the magazine. Paulty has constructed computer models showing how many fish there are off West Africa. The decline of fishing mirrors similar models showing what happened to cod stocks in the North Atlantic.

Meanwhile, a study by David Conover of the State University of New York in Stony Brook has shown that contrary to popular belief it is the big fish that should be returned to the sea rather than the smaller ones if fish stocks are to be best conserved. Conover carried out research where he raised populations of Atlantic silverside fish in laboratory tanks and removed either the largest 90 per cent of fish in each generation or the smallest.

According to New Scientist, within four generations of taking larger fish, individual adults averaged 1.05 grams compared with 6.47 grams if the tiddlers were taken. The total biomass of the fish also dropped if the bigger ones were taken, while it went up if only smaller ones were taken.

Conover believes that current policies of taking larger fish and throwing the smaller ones back is giving rise to a selection pressure for slower-growing fish. "That's bad news for fishery managers who throw back small fish to allow them to grow to maturity in the hope that it will keep fish populations at sustainable levels," the magazine says.