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Snakes
INDEX
LONG TAILS
WHAT ARE SNAKES AND WHERE DID THEY COME FROM?
SNAKE FEATURES
SNAKE SENSES
BOA CONSTRICTORS
BAHAMIAN SNAKES AND CONSERVATION
LONG TAILS
Snakes have been given the bad rap since ancient times. They have been perceived as sinister, deceptive and even evil creatures. Many stories have been made about these animals, from their forked tongue to their legless bodies. Snakes also play a major role in the stories about early man from a range of cultures, some negetive stories and some positive.
All in all, snakes obviously have left quite an impression on mankind throughout time.
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WHAT ARE SNAKES AND WHERE DID THEY COME FROM?
Snakes are reptiles and all reptiles evolved from amphibians. The very first reptiles appear in the geological records some 300 million years ago, when a group of amphibians developed the shelled egg. This egg could be laid on land and therefore, these animals were less dependent upon water for reproduction. Hence, reptiles began to rule the land for nearly 200 million years. It is believed that snakes descended from a group of lizards during this time.
Although it is
debated
, scientists believe that a group of monitor-like lizards began living in underground tunnels. Over millions of years they started to lose thier legs and their outer ear so that they could move more easily underground. Today, snakes are a very successful group of animals with a total of 3,000 species. They can be found on nearly every continent of the world (except Antartica) and in most habitat niches (ie. under the ground, on the ground, in the trees and even in water).
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SNAKE FEATURES
Snakes have strange looking bodies but upon close examination, they have similar body parts to humans, such as a backbone, heart, stomach, etc. However, the snakes body is long and thin and so many of their organs are also long and thin. The available space inside the snake body is limited and so some organs are reduced in size or are even missing all together. For example, some snakes have one large lung and one tiny lung; some only have one lung.
Every snake is quite strong for its size. Pound for pound, snakes have more muscles than most animals. Snakes also have more bones in their backbone than most animals. Humans have 32 or 33 vertebrae in their backbone but some of the larger snakes have as many as 500! Generally, the more bones the snakes have in their backbone, the more agile they are. Agility mixed with strength allows snakes to easily
maneuver
around their environment.
Snakes may get around easily but snakes do not chase their prey. They prefer to surprise it. Snakes are usually well camouflaged with their surroundings and this makes it easy to sneak up on prey or sit and wait for the prey to come to them.
The main feature that separates snakes from lizards is probably one of the most important adaptions of the snake; their jaws! Snakes have jaws that are very
flexible
, enabling the snake to swallow objects several times the snakes own diameter.
Snakes generally have two different ways in which they kill their prey:
- Constriction
The snake wraps its body around the prey and squeezes around the lungs, tightening every time the animal breathes outward, eventually sufficating the prey and then swallows it whole.
This is typical of all boas and pythons. These snakes have teeth that are all uniform in size. The earliest snakes used this method of killing prey.
- Venom
Some snakes have evolved the ability to inject venum into their prey and have fangs to do so. There are different types of fangs:
- Rear fanged snakes - thought to be the first evolved method of venom transport, these fangs do not inject venom but have grooves to "deliver" the venom.
- Front fanged snakes with fixed fangs - thought to have evolved next, these fangs still only have grooves but the movement of the fangs to the front makes it easier to deliver the venom.
- Front fanged snakes with retractible fangs - these are the first fangs which totally enclose the venom and therefore give a real "injection". As they are retractible they can be much larger.
All animals shed their skin but not quite like the snake. Most animals shed their skin in tiny flakes but the snake sheds the whole skin in one go. As the old skin cells break away from the new skin cells underneath, the snake goes cloudy in coloration. When the skin is ready to come off, the snake will rub its head on a hard object to start the peeling process. The whole skin can take up to 5 days to completely shed but generally the process is completed within a day or two.
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SNAKE SENSES
Snakes have amazing senses for getting around and finding their prey:
- Sight - Their eyesight is not very good, it only detects movement.
- Hearing - Their hearing is not very good either. This is because they lack the middle and outer parts to the ear. However, they can hear via vibrations through the ground. It is also possible that the enlarged lung may play an important role in the amplification of vibrations in their body.
- Smell - The sense of smell in the snake is amazing.
 They smell through their nose, like most animals, but they also use their tongue to capture particles in the air. Then they place those particles onto a special spot on the roof of their mouth called the Jacobson's orgin.
Snake tongues divide at the end, forming two tips. This simply helps to increase the surface area of the tongue so that the snake can pick up as many particles as possible.
Their sense of smell is so good that a snake can follow the scent of an animal 2 days after it has been in that area!
- Heat (infared) - Some snakes (eg. boas, pythons and pit vipers) have tiny holes along the top of the mouth, called pits. These can detect heat and is very useful when locating animals in the dark. It is now thought that the snakes project this infrared image so that they even "see" a warm blooded animal as a ball of fire.
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BOA CONSTRICTORS
The boa constrictors and the pythons make up the family of snakes known as the boidae. All the snakes in this group use the constriction method of feeding. This is an old group of snakes and the first snakes were probably very similar. The largest snakes in the world are in this family (the longest snake in the world being the Reticulated python and the heaviest snake is the Anaconda) but not all members of this family are necessarily big.
Boa vs. Python
Boas and pythons have differences of bone structures in the head and they differ by how they produce their young. Most snakes, like the pythons, lay shelled eggs. This is known as oviparous birth. Boa constrictors however, retain their eggs inside, which provides a safe environment for the eggs. The young hatch inside the mother and emmerge as little snakes. This method of birth is known as ovoviviparous. This is different from an aminal which gives true live birth (where the young are connected to the mother by an umbillical cord), known as viviparous birth.
A general rule of thumb to distinguish boas from pythons is the fact that boa constrictors are found in the Americas (new world) and pythons are found in the Asia, Africa, Australia (old world). There are a few exceptions to this rule, such as the sand boas of Africa and the ground and tree boas of Madagascar.
The lost legs
Boa constrictors have one interesting feature that many other snakes do not; remnants of legs! Snakes lost their legs millions of years ago but the boa constrictors have part of their hind legs still left behind. They are little claw-like structures called spurs. The spurs are connected to the pelvis and are moveable. The males have larger spurs than the females. The male uses the spurs to "tickle" the female in order to stimulate them into breeding. The spurs are also used to "grasp" hold of the female during mating.
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BAHAMIAN SNAKES AND CONSERVATION
The Bahamas has a total of five different types of snakes.
- Bahamian Boa constrictors - (Boidae)
- Brown racers - (Colubridae)
- Pygmy boa constrictors - (Tropidophiidae)
- Worm snakes - (Typhlopidae)
- Blind snake - (Leptotyphlopidae)
Bahamian Boa Constrictors
(Epicrates sp.)
-
Threatened species
These beautiful, mottled grey-brown snakes belong to the genus Epicrates, which is part of a group of snakes known as the rainbow snakes. The rainbow snakes are so called for their irridescent shine that can be seen in the sunlight.
The name "Epicrates" literally translated means "slim snake" and as indicated this means that these snakes do not get very thick in diameter like many other boa constrictors. These snakes can grow upto 8 feet in length. There have been many stories of these snakes getting to a much larger size, however, upon inspection these reports have proved to be an exaggeration.
These boas are very adaptable and can be found in a range of habitats. Younger boas are often found in trees waiting to ambush prey. Older and bigger boas are found throughout the forest and often near brush piles. The young boas tend to feed mainly on small insects and lizards. When they grow bigger they can kill larger prey and this includes rodents, frogs, larger lizards (including young iguanas), small birds and even other snakes.
The Bahamas has a total of three species and seven sub-speceis of this type of boa constrictor. The different sub-species and the islands that they are found are shown in the map to the below.
The Ragged Island boas were not discovered until 1957. The Acklins Island boa has never been caught alive.
Bahamian boa constrictors are all considered to be threatened with extinction. They fall under the CITES appendix II, which means that they are on their way to becoming endangered with extinction. Their current status is due to the fact that they are heavily feared and therefore killed on-sight in the Bahamas. There are many false stories about these snakes that have been passed on throughout the ages. One popular belief is that they hunt down pregnant women for their milk. This is widely believed and is quite amusing considering that reptiles do not drink milk!
Brown racer
(Alsophis vudii)
This snake belongs to group of snakes known as the Colubrids. Over half of all snakes fall into this group, making it the largest family of snakes. Colubrids are represented throughout the whole of the West Indies. Their ancestors are believed to have come from Central and South America. The Alsophis genus has 16 different species and collectively they are known as the West Indian racers, as they are the most widely distributed of all the Colubrids in the West Indies. They are found in the Bahamas, the Greater Antilles, the Cayman Islands, and the Lesser Antilles south to Dominica, with one species in South America and another in the Galapagos Archipelago, in the Pacific Ocean. These snakes are rear-fanged vipers, and carry only a small amount of toxin that can only bring down a very small animal and are not a concern for humans. These snakes tend to feed on small cold blooded animals such as lizards, frogs, and other snakes. Most members of this genus are very common where they occur, except on the islands where Mongooses have been introduced (i.e. in Jamaica).
The Bahamian Brown Racer is the most common snake on the majority of Bahamian islands. Like all racers they are fast moving snakes and will even pursue their prey with agility and speed on the ground as well as in the trees. This snake very rarely bites humans but instead prefers to use its speed to flee from them.
There is another racer found on the Bahamian islands, the Hispaniola lesser racer (Antillophis parvifrons). This racer is mostly found in Haiti and the Dominican republic but is less commonly found on many other islands in the West Indies such as the Bahamas, Jamaica and Cuba.
Bahamian Pygmy Boa Constrictor
(Tropidophis canus)
This snake belongs to a family of snakes known as the Dwarf boas. Though these snakes are closely related to the boa constrictors and pythons, they are not traditionally classified in the Boidae family. However, genetic studies are showing that these snakes are more closely related to the boas than previously thought.
The family is confined to the neotropics (tropical Americas), with the greatest diversity being in Cuba where new species are being discovered frequently. These snakes are very small, averaging to about 30-60 cm in total length. Most species spend their day burrowed underground or under vegetation, surfacing only at night or when it rains. Some species are arboreal (tree dwelling) and are often seen hiding in bromeliads in trees. Dwarf boas have the ability to change color from light (when they are active at night) to dark (when they are inactive in the day). This color change is brought about by the movement of dark pigment granules.
The dwarf boas display some interesting behaviors. When they feel threatened, they will coil up into a tight ball, as seen in several other snakes, like the ball pythons. On Andros Island in the Bahamas, the local name “shame snake” may refer to this behavior. A more peculiar defensive behavior observed by these snakes (and also observed by previous captive dwarf boas in Ardastra Gardens) is the ability for the snake to voluntarily bleed from the eyes, mouth and nostrils.
The Bahamian Pygmy boa has an unusual yellowy-orange tip on its tail, which has been observed to lure prey. This species almost entirely feeds on small lizards and the occasional small frog.
The Turks and Caicos pygmy boa (Tropidophis greenwayi) is also found on some of the Southern Bahamian islands. This pygmy boa is very similar to the Bahamian pygmy in appearance.
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