The small water snake has found a way to startle its prey so that the fish turn toward the snake’s head to flee instead of turning away. In addition, the fish’s reaction is so predictable that the snake actually aims its strike at the position where the fish’s head will be instead of tracking its actual movement.
"I haven't been able to find reports of any other predators that exhibit a similar ability to influence and predict the future behavior of their prey," says Kenneth Catania, associate professor of biological sciences at Vanderbilt University, who has used high-speed video to deconstruct the snake's unusual hunting technique.
His observations are published this week in the online early edition of the Proceedings of the National Academy of Sciences.
Catania, who is the recipient of a MacArthur “genius” award, studies the brains and behavior of species with extreme specializations. He was attracted to the tentacled snake because it is the only snake that comes equipped with a pair of short tentacles on its nose and he was curious about their function.
“Before I begin a study on a new species, it is my practice to spend some time simply observing its basic behavior,” Catania explains. The snake forms an unusual “J” shape with its head at the bottom of the “J” when it is fishing. Then it remains completely motionless until a fish swims into the area near the hook of the “J.” That is when the snake strikes.
The snakes’ motions take only a few hundredths of a second and are too fast for the human eye to follow. However, its prey reacts even faster, in a few thousandths of a second. In fact, fish are famous for the rapidity of their escape response and it has been extensively studied. These studies have found that many fish have a special circuit in their brains that initiates the escape, which biologists call the “C-start.” Fish ears sense the sound pressure on each side of their body. When the ear on one side detects a disturbance, it sends a message to the fishes’ muscles causing its body to bend into a C-shape facing in the opposite direction so it can begin swimming away from danger as quickly as possible
Catania is the first scientist to study this particular predator-prey interaction with the aid of a high-speed video camera. When he began examining the movements of the snake and its prey in slow motion, he saw something peculiar. When the fish that the snake targets turn to flee, most of them turn toward the snake’s head and many literally swim into its jaws! In 120 trials with four different snakes, in fact, he discovered that an amazing 78 percent of the fish turned toward the snake’s head instead of turning away.
Next, the biologist noticed that the first part of its body that the snake moves is not its head. Instead, it flexes a point midway down its body. Using a sensitive hydrophone that he put in the aquarium, he confirmed that this body fake produces sound waves intense enough to trigger the fish’s C-start response. Because these sound waves come from the side opposite the snake’s head, this reflex action drives the fish to turn and swim directly toward the snake’s mouth.
“Once the C-start begins, the fish can’t turn back,” Catania says. “The snake has found a way to use the fish’s escape reflex to its advantage.”
As he studied the snake’s actions even closer, he made an even more remarkable discovery. When it strikes, the snake doesn’t aim for the fish’s initial position and then adjust its direction as the fish moves – the way most predators do. Instead it heads directly for the location where it expects the fish’s head to be.
“The best evidence for this is the cases when the snake misses,” says Catania. “Not all the targeted fish react with a C-start and the snake almost always misses those that don’t react reflexively.”
Catania’s next step will be to determine whether this predictive capability is hard-wired or learned. To do so, he hopes to obtain some baby snakes that have just hatched and videotape their first efforts to catch prey.The research was supported by a grant from the National Science Foundation.
[Note: To view the high-speed video go to http://sitemason.vanderbilt.edu/news/video/2009/06/18/video-tentacled-snake-in-action.82827]
David F. Salisbury | Newswise Science News
How gut bacteria can make us ill
18.01.2017 | Helmholtz-Zentrum für Infektionsforschung
Nanoparticle Exposure Can Awaken Dormant Viruses in the Lungs
16.01.2017 | Helmholtz Zentrum München - Deutsches Forschungszentrum für Gesundheit und Umwelt
Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.
While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...
Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales
Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...
Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.
As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...
At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).
Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...
Many pathogens use certain sugar compounds from their host to help conceal themselves against the immune system. Scientists at the University of Bonn have now, in cooperation with researchers at the University of York in the United Kingdom, analyzed the dynamics of a bacterial molecule that is involved in this process. They demonstrate that the protein grabs onto the sugar molecule with a Pac Man-like chewing motion and holds it until it can be used. Their results could help design therapeutics that could make the protein poorer at grabbing and holding and hence compromise the pathogen in the host. The study has now been published in “Biophysical Journal”.
The cells of the mouth, nose and intestinal mucosa produce large quantities of a chemical called sialic acid. Many bacteria possess a special transport system...
10.01.2017 | Event News
09.01.2017 | Event News
05.01.2017 | Event News
17.01.2017 | Earth Sciences
17.01.2017 | Materials Sciences
17.01.2017 | Architecture and Construction