CROTALUS POLYSTICTUS PDF

Compared to most snakes, they are heavy-bodied, although some African vipers are much thicker. The rattle may also be lacking in any species due to a congenital abnormality. In most other snakes, the tail tip, or terminal spine, is cone-shaped, hardly any thicker than the rest of the skin, and is shed along with it at each successive molt. In this case, however, the end-scale, or "button", is much thicker and shaped like a bulb, with one or two annular constrictions to prevent it from falling off. Before each molt, a new button will have developed inside the last one and before the skin is shed off its body, the tip of new button shrinks, then loosening the shell of the previous one.

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Compared to most snakes, they are heavy-bodied, although some African vipers are much thicker. The rattle may also be lacking in any species due to a congenital abnormality. In most other snakes, the tail tip, or terminal spine, is cone-shaped, hardly any thicker than the rest of the skin, and is shed along with it at each successive molt. In this case, however, the end-scale, or "button", is much thicker and shaped like a bulb, with one or two annular constrictions to prevent it from falling off.

Before each molt, a new button will have developed inside the last one and before the skin is shed off its body, the tip of new button shrinks, then loosening the shell of the previous one. This process continues so the succession of molts produces an appendage consisting of a number of interlocking segments that make an audible noise when vibrated. Since younger specimens may shed three or four times in a year, every time adding a new segment to the rattle, the number of segments bears no relation to the age of the snake.

In theory, the rattle could become very long indeed, but in practice, the older segments tend to wear out and fall off. In captive specimens, however, as many as 29 segments have been found. However, most species defend themselves readily when cornered.

Obviously this depends on the size of the animal, but other factors may also play a role, such as the species, the position of the body, and the degree of excitement. Additionally, the question of definition exists: from which point on the snake should a strike be measured: from the front, the middle, or the back of the anchor coil on the ground?

Even if the length of the specimen is known, once it strikes, it is almost impossible to determine the limiting point reached by its head and the position of its body when the movement started. Therefore, it is not surprising that many conflicting statements can be found in the available literature about how far these snakes can strike. Estimates have been given that range from one-third of the body length, to half, three-quarters or even the full length of the animal. They rarely strike further than half of their body length, and almost never more than three-fourths, but it is still not wise to trust such values if only because it is not possible to accurately judge the length of a coiled snake.

Smaller species feed mainly on lizards, while larger species start by feeding on lizards as juveniles and then switch to preying mainly on mammals as adults.

Prey items more frequently taken include rabbits, ground squirrels, tree squirrels, chipmunks, prairie dogs, gophers, and rats and mice, [11] while those less frequently taken include birds, snakes, and amphibians.

Cannibalism has been reported in a number of different species. Individuals that feed on rodents usually release their prey after a strike, and these snakes evidently can discriminate between trails left by prey that has or has not been envenomated. These include other snakes, such as kingsnakes Lampropeltis , coachwhips Masticophis , indigo snakes Drymarchon and racers Coluber , birds, such as hawks, eagles, owls, roadrunners, and ravens, and mammals, such as coyotes, foxes, wildcats, badgers, skunks and pigs.

Two cases were reported in which dead hawks found near venomous snakes had suffered hemorrhage and gangrenous necrosis due to snakebite. Females at an age of 26 months undergo vitellogenesis as they enter their third hibernation , [13] mate the following spring, and give birth later in September or October. In North America, the females of some species store sperm in their oviducts for at least eight months, and the males all species of which undergo spermatogenesis during the summer store sperm in the vas deferens for at least a year.

Thus, species that store sperm for a shorter duration mate in the spring and store sperm in the vas deferens, while those that do so for a longer duration mate in the fall and store sperm in the oviduct over the winter, after which fertilization occurs the following spring. Those found in central and southern Mexico or the tropics have reproductive cycles that correspond mostly with the rainy season.

First, zinc-containing metalloproteases act upon capillary endothelial cells to cause platelet aggregation and hemorrhage. Firstly, endothelial-cell disruption causes lysis and internal bleeding. Then, as these hemorrhages increase, the natural thrombin response is hindered by the effect of crotalin increasing the toxic effect. Their observed hunting technique is a bite-and-release method, so a fast-acting toxin would be ideal.

Assuming the natural median prey would be a small rodent such as a mouse, the bite would elicit a fear response, quickening heart rate and increasing blood pressure. This would speed the toxic effect, as well as spread the hemolytic and hemorrhagic effects.

Neurotoxic effects may also be caused by rattlesnake venom. These effects vary by species, and within species by population.

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