And more about snake senses
How do snakes find prey?
Snakes use a combination of senses, relying especially on smell.
Smell: is the most important snake sense. A snake has a regular nose and analyses smell the way all other animals do. But snakes have a second highly developed smell sense (vomeronasal), which some lizards also have. A snake uses its forked tongue to pick up chemical traces. The tongue is then inserted into pits on the roof of the mouth (called the Jacobson's organ) It is this organ that analyses the chemicals, and not the tongue, which has no taste or smell buds.
A snake's tongue cannot
sting, prick or jab!
Unlike lizards, a snake's tongue is not used in swallowing prey
A snake may also use
its tongue to feel things
(since it has no fingers!)
Eau de Serpent: Some prey use snake scents to protect themselves! When Siberian chipmunks (Eutamias sibiricus asiaticus) come across a dead snake, they will chew up bits of the snake skin and roll around to smear it all themselves. They also smear themselves with snake urine or faeces when they can. In studies, snakes were less likely to attack Siberian chipmunks which were perfumed with snake bits or snake excretion. From William Agosta's "Bombardier Beetles and Fever Trees: a close-up look at chemical warfare and signals in plants and animals"
There is a notch on the upper lip (rostral groove) so the tongue can flick in and out while the mouth remains closed. Because the tongue is forked, a snake can tell the direction of a chemical trace. Smell is also the primary way that snakes attract and find mates.
The snake's taste buds are near its teeth and comes into action only when the prey is in the mouth. In fact, a snake relies on smell to choose it's food. Captive snakes can often be persuaded to eat untraditional food simply by smearing the food with the scent of its usual prey.
Heat (infrared) is another important sense, especially for night-hunting snakes. The twinned sensors not only allow snakes to judge distance, but may also give an "image" of the size and shape of the prey. This allows them to strike accurately at warm-blooded prey in the dark. There are indications that some snakes can superimpose the infrared image on a visual image. Those snakes that prey on "cold-blooded" creatures are believed to detect the "heat void" created by the prey in the background temperature!
Heat sensing is most highly developed in pit vipers. They have heat-detecting sensors concentrated as two large pits between their nostril and eyes. These pits can detect temperature differences as slight as 0.02 degrees C.
In boas and pythons (right), these are cruder, smaller and distributed on the lips on either side of the head. But they work in the same way as the pit viper's. But some snakes have very good vision. Some can change the focus of their eyes to create a clear image. Some (like Vine snakes) have good 3-D vision to judge distances because their eyes are at the front of the head; these snakes hunt in the day or move around in trees. Others with eyes on the side of their heads have a wider field of vision. Most night-hunting snakes have larger eyes and vertical pupils which enhance night vision (although some day snakes also have these). Some burrowing snakes like blindsnakes have simple eyes that can only detect light and dark. Sight: Although most snakes have good eyesight, snakes don't rely only on sight alone. Most snake eyes are best at detecting movement. Snakes have been known to glide past creatures that remain motionless. Snakes don't hypnotise their prey: Perhaps this myth arose because snakes don't blink and animal prey know that standing still is the best chance to avoid being attacked.
While some snakes may see some colours, most don't appear to sense colour the way we do. Perhaps this is why snakes don't display vivid colour changes during mating like some other reptiles.
Hearing: Snakes can hear but this sense is not as well-developed as its other senses. Unlike lizards, snakes don't have external ears or even a middle ear. They only have a small bone (columella) which connects the jaw bone (quadrate bone--coloured orange in diagram) to the inner ear canals. These inner ear canals work superbly as the snake moves in three dimensions! A snake picks up sound through the skin which passes on to this jaw bone. Indications are that it is not true that a snake can only hear sounds when its head is on the ground. Snakes can hear airborne sounds, though probably not as acutely as some other animals. There are also indications that the lung may act as a sound receptor.
Other senses we know nothing about: The tropical Olive Seasnake (Aipysurus laevis) has recently been found to have a light receptor on its tail. Its function is not known. Snake can also navigate long distances suggesting that they have some sense of the Earth's magnetic field.
How do snakes catch prey?
Hunting techniques: Because snakes are ectothermic, they're slow and cannot be active for long. So they rely heavily on stealth and surprise. Ambush: The snake will choose a spot where prey are likely to be; next to rocks where lizards sun themselves; at the entrance of caves used by bats-the snake strikes out as the bats fly by; next to ripening fruit which attract birds and mammals.
To remain unnoticed until the prey comes within reach snakes rely on camouflage or hide themselves: sand boas bury in dirt or sand; anacondas lie submerged with only their eyes and nose above water. Most snakes lunge out at the last moment to seize prey. Some use lures: wriggling their brightly coloured worm-like tails to attract frogs and lizards within striking range; most lose this ability once they "graduate" to mammals. Some snakes, upon locating a prey will actively stalk and sneak up on it.
Some just use brute force: large tree snakes jump onto their prey from branches, snake and prey crashing onto the ground. Some snakes anchor their tails before lunging out so they can retract to a safe position to eat their prey.
Foraging, prowling, hunting: This involves more active moving to regularly patrol a territory, checking regular nest-sites for new babies, regular sleeping spots for prey. Foraging is more effective when prey don't travel far from one small area so the snake has to go to the prey. It is also profitable when prey is less active and more easily trapped (nesting, incubating eggs, sleeping). Ambushing is cost-effective only when there is abundant moving prey, although some snakes will wait for weeks at a one spot. Ambushing is preferred by heavier snakes, probably because foraging is riskier and more costly in terms of energy. Because such large snakes need to eat big prey and it takes a long time to swallow large prey, ambushing is preferred as it allows such snakes to choose a spot where they will be less vulnerable to predators while they are consuming its prey.
A snake may use a combination of these techniques. It may change its method with the seasons to keep up with changes in the quantity and distribution or prey and the amount of heat available to maintain its own body temperature and energy level.
More about snakes
- What are snakes?
- Are snakes cold?
- Why are snakes long?
- What do snakes eat? Do they drink?
- How do snakes swallow?
- How do snakes hunt?
- Why and how do snakes kill?
Snake predators and how do snakes protect themselves?
Snake mating, eggs and babies
Where are snakes found?
Fascinating snake adaptations to various habitats
Snake bites and first aid
Snakes in danger: role and conservation and snakes in human culture
Snake records: biggest, smallest, deadliest and more
- More snakes
- More animals
- General snake links and references
Further informations in german can be found here!