Boa Constrictors Know When To Stop Squeezing By Monitoring Heartbeat Of Prey

Boas and other constrictors kill by literally squeezing the life out of their prey--no secret there. But how do they know when to stop squeezing?

With the help of a bunch of hungry boas and a tempting smorgasbord of rats, scientists at Dickinson University in Pennsylvania have found the answer: Through their tightly wrapped coils, thesnakes can feel the heartbeat of their prey--and they stop squeezing once the hearts stop beating.

It's lucky for that the snakes have this ability, the scientists point out in their macabre study. Why? Because the snakes expend huge amounts of energy when they squeeze--and stopping squeezing as soon as possible helps prevent precious calories from being wasted. What's more, the snakes are more vulnerable to attack by predators--or even the prey the're trying to subdue--when they're busy squeezing.

For the study, published in the journal Biology Letters, Dr. Scott Boback and his team put wild and captive-born snakes through their paces. To make their measurements as accurate as possible, the biologists offered the snakes not wildly thrashing live rats but cadaveric (dead) rats fitted with simulated hearts (water-filled bulbs made to pulsate via pump).

What happened next was pretty dramatic.

"I couldn't believe my eyes the first time we tested a snake with a rat with a simulated heart," Dr Boback told BBC Nature. "It was writhing and squeezing the rat in an apparent effort to kill it."

And the longer the artificial hearts kept beating, the longer the boas kept up the pressure. According to Discover magazine, the pressure is now on biologists to explain exactly how the snakes evolvedto have this heart-sensing ability.

Black Hole Picture, Never Before Possible, To Be Planned At University Of Arizona Conference

At the center of our galaxy, an enormous black hole has worked invisibly for billions of years, and now scientists are gearing up to snap its picture.

A conference will be held to discuss the never-before-attempted photographic gambit on January 18 at the University of Arizona (UA). There scientists will map out an interstellar imaging project that astronomers of previous decades never could have imagined.

Why unimaginable? According to the statement,

Even though the black hole suspected to sit at the center of our galaxy is a supermassive one at 4 million times the mass of the sun, it is tiny to the eyes of astronomers. Smaller than Mercury’s orbit around the sun, yet almost 26,000 light years away, it appears about the same size as a grapefruit on the moon.

Getting the picture will be a herculean task. The team will connect 50 telescopes of all sizes, from Hawaii to the South Pole, and use them as components of a single, enormous virtual telescope. The Event Horizon Telescope, as the project is called, will bring scientists "as close to the edge of black hole as we will ever come," according to the telescope's website. "In essence," said Sheperd Doeleman, principal investigator of the project, "we are making a virtual telescope with a mirror that is as big as the Earth."

Dimitrios Psaltis, co-organizer of the conference and associate professor of astrophysics at UA's Steward Observatory, spoke of the project in ambitious terms. "We need the entire world to come together to build this instrument because it is as big as the planet," he said. "People are coming from all over the world because they have to work on it."

And for good reason: the black hole image will verify or disprove a part of Albert Einstein's theory of general relativity. General relativity predicts that the swirl of dust and gases around a black hole—which is all the telescope will be able to see, since the hole itself is, of course, black—should form a perfect circle. If it looks even slightly distorted, we may have to rethink parts of Einstein's important theory.