Introduction to Reptiles

Transcription

1 Advanced Snakes & Reptiles 1 Module # 1 Component # 1 Introduction This Course is designed for those seeking an in-depth look at Herpetology (Reptiles) and Snakes in particular. The Course has the following outline: Module # 1 Reptilia (The Reptiles) Component # 1 Reptile specialisation, myths & glossary Module # 2 Chelonia (Shield reptiles) Component # 1 Chelonian structure, sense & breeding Component # 2 Tortoise Species & Identification 6 Species Component # 3 Terrapin Species & Identification 4 species Module # 3 Crocodiles, Lizards, Chameleons Component # 1 Species identification Module # 4 Serpentes (The Snakes) Component # 1 Introduction to Snakes Component # 2 Blind and Thread snakes Component # 3 Pythons Component # 4 Burrowing snakes Component # 5 Typical Snakes Part # 1 Component # 6 Typical Snakes Part # 2 Component # 7 Typical Snakes Part # 3 Component # 8 Cobras and Mambas Component # 9 Vipers and Adders Component # 10 Un-resolved species Module # 5 The E-Book Snake Identification Software Component # 1 Purchase the E-Book Snake Identification Software Module # 6 First Aid for Snake Bite Component # 1 First Aid for Snake bite

2 Advanced Snakes & Reptiles 2 Myths & Superstitions Despite the snake being symbolized by the medical profession in the form of the caduceus or magic wand of the Greek god Hermes, there is a huge amount of fear and misunderstanding of reptiles. Most times a snake is encountered, the person discovering the snake becomes panicked and frightened, screams or runs away. Frequently the snake is unnecessarily killed. Most often (statistically) the snake is totally harmless to humans and is, in fact being useful by controlling rodents in the area, particularly around human habitation. Certainly they may (although seldom) inflict bites and they may be potentially life threatening, but far less people die from snake bites than from bee stings, there are more people killed by lightning in a year than by venomous snakes. Many species of snakes are unfortunately restricted to the ground and cannot stay out of our way. There is surprising similarity between a Brown House Snake (Lamprophis capensis) and a Black Shouldered Kite, excluding physical appearance of course. They both hunt rodents and cannot inflict any great harm on us. The bird however is mostly seen in areas that we do not use, such as trees, in the air or perched on telephone lines. What exacerbates an irrational fear of reptiles and particularly snakes is the wealth of commonly held belief, misconceptions, superstition, myths, embellished anecdotes, urban legend and blatant fabrications that surround them. Here are a few of the commonly heard examples followed by a rational perspective. Are tortoises used by Sangoma's (traditional witch doctors)? Yes. There is a belief that because the shell protects the tortoise this protection will be passed across to them. Tortoises feet are often used for digging, and thus some believe they solve a problem quicker by using these feet in tribal ritual. Are all snakes venomous? No. Of the ±140 endemic species to Southern Africa, only about 10% are venomous enough to be considered medically important from a human perspective. Do snakes move in pairs? No. Snakes and most reptiles are solitary animals and will only seek out other specimens in the breeding season to breed. They definitely do not travel together. Once mating is complete they move off in separate directions.

3 Advanced Snakes & Reptiles 3 Do snakes seek out revenge when you have killed one of a pair? No. The pairing myth may stem from the phenomenon of certain species of female leaving scent trails for males to find and following as part of their reproductive activity. Those encountering the female and soon after the following male may incorrectly conclude pairing. Are chameleons venomous? No. They are totally harmless and cannot impose any real damage on anyone. The origin of this belief is not conclusively documented. Why are some indigenous peoples scared of Chameleons? One traditional belief is that when a person dies their spirit goes to the nearest animal to go to the spirit world. If this is a chameleon the spirit will never get there. Another is that because the eyes of the chameleon can rotate independently of one another, an animal can see into the future and the past at the same time is not to be trusted. Do snakes crush their prey, particularly pythons? No. Constrictors do not crush their prey at all. It would be risky during swallowing to have broken bones in the prey as they could penetrate the snake's internal organs while swallowing. All constrictors do, is to wrap their bodies around their chosen prey, and tighten their coils every time the animal exhales. This action inhibits the ability to inhale so that it cannot get in air and eventually suffocates. Does the Puff Adder (Bitis arietans) strike backwards? No. They do not strike backwards, but rather, extremely rapidly forwards. Having one of the fastest strikes in the world, the forward strike so rapid that it is often not seen when prey / victims are bitten. Does the Black Mamba run faster than a horse? No. The size and speed of snakes is frequently over exaggerated, probably as a result of the fright and panic situation resulting from a random encounter. Most people can out run a snake easily, especially as reptiles can only go at full speed in short bursts.

4 Advanced Snakes & Reptiles 4 Do snakes only die at sunset? No. Most certainly not, they die naturally at anytime or when they get killed. Are snakes slimy? No. They do have a shiny appearance but unless they have just come out of water they are dry and feel dry. Some describe the texture as being very similar to glass. Do snakes sting with their tongue? No. The tongue is used for olfactory (smell) functions. The tongue flickers more frequently when the animal is in a new environment, when people are around or when in search of prey. The forked tongue "catches" air particles and takes them into the mouth where a specialised organ called the Jacobson's Organ is situated. This is in the top of the mouth, which then translates the scents into smells it comprehends. Do snakes lick their prey before swallowing it? No. This belief probably originates from the way a snake will flick its tongue over the entire body of the prey before swallowing. This action allows the snake to accurately discern the animal body shape. This is done to ensure that swallowing of the victim head first, which usually guarantees that all limbs will fold down when swallowed. Are all venomous snakes immune to other snake venom? No. Some snakes seem to have an immunity to venom like the King Snake in America or the King Cobra of India or our Cape File Snake who can even eat Black Mambas (our most venomous species). Even the same species are to a degree immune to their own venom, but it is not always the situation and deaths may still occur. Also venom is a protein and if ingested (swallowed) by a snake, the venom just gets digested. It s when the venom is introduced onto the bloodstream that envenomation takes place. How this results to humans (swallowing venom) is not something that should be independently tested, but the fact that snakes have fangs cannot be ignored. Balance this against the fact that when venom is introduced to eyes (spitting cobras) the envenomation effect is very serious.

5 Advanced Snakes & Reptiles 5 After a snake has bitten or after it has been milked is it harmless? No. This is most definitely not the situation. Snake venom is from modified saliva glands and thus venom is often quickly replenished. What is the difference between venom & poison? Yes. The distinction comes from the mode of delivery into an organism. Snakes are venomous not poisonous, as venom ingested as opposed to injected is not problematic. Poison-arrow frogs (Dendrobatidae) are poisonous not venomous as you may be poisonous by contact or ingesting the animal. Venom can be consumed or placed on the skin with little to no effect. It is a mix of specific proteins that has to get into the blood system to have any effect. A poison however cannot be safely ingested and in some cases even placed on the skin as it is absorbed by the body and results in poisoning or death. Do pythons hang onto trees when killing prey or have a hook attached to the tail used for anchorage? No. Pythons do not have a hook on the end of their tails. They also do not hang onto tree trunks, however if a tree is nearby and the prey is pulling them, they will wrap their tail around a tree or bush. There are many other beliefs and superstitions that exist which are often a problem to reptiles, as they are nearly all negative and result in the animals being persecuted or killed through ignorance. If you ve enjoyed this section, then have a look at our Course on African Folklore.

6 Advanced Snakes & Reptiles 6 Classification and Taxonomy The reasons, importance, methods and usefulness of classification and taxonomy are explored in the Module of the same name that can be found in our Game Ranging Course. Here we simply include the overall catergorisations and organisation of the reptiles endemic to Southern Africa, to the level of cataloguing. Order Crocodylia Sub-Order Eusuchia Crocodylidae Kingdom Animalia Phylum Chordata Class Reptilia Order Chelonia Sub-Order Cryptodira Hidden necked- Tortises Testudinidae (Terrestrial tortoises) Cheloniidae (Marine Turtles) Dermochelyidae (Leatherback turtles) Trionychidae (Soft-shelled terrapins) Sub-Order Pleurodita Side-necked tortoises Pelomedusidae (Terrapins) Sub-Order Amphisbaenia Worm lizards Not covered in the scope of this course Order Squamata Sub-Order Sauria Lizards Varanidae (Monitors) Chameleonidae (Chameleons) Sub-Order Ophidia Snakes Typhlopidae (Blind snakes) Leptotyphlopidae (Thread snakes) Pythonidae (Pythons) Atractaspididae (Burrowing snakes) Colubridae (Typical snakes) Elapidae (Fixed frontfanged snakes) Viperidae (African adders) Unresolved (Species not classified)

7 Advanced Snakes & Reptiles 7 Species example Here is the full taxonomic classification of an individual species, in this case the Puff adder. Kingdom Animalia Phylum Chordata Class: Reptilia (Reptiles) Order: Squamata (Scaled reptiles) Suborder: Serpents (Snakes) : Viperidae (Adders and vipers) Subfamily: Viperinae (True vipers) Genus: Bitis (African Adders) Species: arietans (Puff adder) Subspecies: arietans (Typical puff adder)

8 Advanced Snakes & Reptiles 8 Characteristics Reptiles are masters of survival, some originating back to the dinosaur era with relatively little change over the millions of years. This is not purely by chance, but more due to a couple of specialised attributes. These are: 1. Ambush 2. Ectothermy (cold-blooded) Ambush The majority of reptiles are predators / hunters. The most successful hunters attack by surprise by using a combination of camouflage, habitat and silence and therefore they are one of the worlds ultimate predators. For instance Nile Crocodiles (Crocodylus niloticus) ambush prey from under the water, the Puff Adder (Bitis arietans arietans) lies in wait for unsuspecting prey to move within striking distance, the slow moving chameleon with a lighting fast tongue that is accurate over a relatively long distance. A lot of the time this method of hunting uses up fairly low amounts of energy, particularly if you compare it to a long fruitless chase by a cheetah. This method of hunting effectiveness is aided by the most important factor of their survival, being "cold blooded". Ectothermy The term "cold blooded" is not really 100% correct, although it is a general term that reptiles have been classified under. They actually vary from being "coldblooded" to "hot-blooded". A Rinkhals (Hemachatus haemachatus) in the middle of winter in a burrow will most certainly be "cold-blooded", but on a hot summers day basking in the sun, it's body temperature will often be higher than that of most warm-blooded animals. The better correct term would be that they are ectothermic. There are other terms used to describe ectothermic such as Exothermic and Poikiothermic, but for the purpose of this course we are only using ectothermic. The term means that they are reliant on outside heat sources. The word originates from the Greek word ectos, meaning outside and therme meaning heat. The general misconception is that Ectothermy as opposed to Endothermy (warmblooded) represents a lower form of evolution and thus overall inferior. Therefore asked why this is of any real benefit to them?

9 Advanced Snakes & Reptiles 9 When we examine most mammals, we find that they use approximately 80-90% of their food intake to generate internal body heat. Thus reptiles by comparison only have to eat 10-20% of the amount of food of the equivalent sized mammal. This for a reptile is adequate to "generate" the heat required for activity which is accomplished with very little effort, other than to find a spot in the sun. Not only do they need to eat less, they can eat less frequently than mammals. Periods of drought or adverse climatic conditions affects them less severely than mammals which most certainly aids in their continued survival. A few examples are: 1. Hatchling egg eaters have been recorded to survive for a year without any food, surviving only on the food absorbed while in the egg and from the egg sac after hatching. 2. Pythons in captivity have been recorded not to eat for a year, or only be fed a couple of large meals. In the wild an adult Southern African Python (Python natalensis) may only have 2-4 large meals per annum. This applies to other snakes, crocodiles, monitors & chameleons. For some species this is great importance, particularly if frogs are your main diet. Species like the Common Night Adder (Causus rhombeatus) or the Red-Lip / Herald Snake (Crotophopeltis hotamboeia). Frogs are only active during the rainy season. In the winter they will hibernate and in a time of drought they will keep their body temperature as low as possible until food is available. Now one may ask what about chelonians (Tortoises & Terrapins). They do need to feed more regularly than the above but in comparison to mammals of the same size, they eat far less. This must not obscure the disadvantages of Ectothermy vs. Endothermy, after all, being able to generate your own body heat was one of the main reason why mammals out competed reptiles to become the dominant terrestrial group. Suffice to say cold-bloodedness in reptiles need simply to be considered within the context of their own ecology.

10 Advanced Snakes & Reptiles 10 Characteristics There are six predominantly common attributes among the Class Reptilia, these are: 1. Four legs 2. Egg laying (oviparous) 3. Insect Eaters 4. All species have scale covering to lesser or grater degree 5. They never stop growing 6. Low water demand (as they have no sweat glands) There are key differences between the various groups of reptiles as shown below, Not all species within the group (e.g. snakes) conform to the characteristics listed. Description Snakes Lizards Monitors Chameleons Tortoises & Turtles Crocodiles Moveable eyelids No Yes Yes Yes Yes Yes Four legs No Yes Yes Yes Yes Yes Ovoviparity Yes No No No No No Egg laying Yes Yes Yes Yes Yes Yes Retractile tongue Yes No Yes No No No External ears No Yes Yes Yes Yes Yes Protective shell Single row (Ventral scales) Several rows (Ventral scales) Tail regeneration No No No No Yes No Yes No No No N/A No No Yes Yes Yes N/A Yes No Yes No No No No Operational lungs

11 Advanced Snakes & Reptiles 11 Notes: 1. Retractile tongue refers to the use of the tongue for "smelling" rather than for hunting 2. Diapsid Skull - Basically this is an old form of the skull having two openings in the skull behind each eye. 3. Anapsid Skull - These skulls have evolved and are more "light weight" characterized by having no opening in the temporal region of the skull. Excess or unnecessary bone is no longer present.

12 Advanced Snakes & Reptiles 12 Glossary All Science and especially the natural sciences have an affinity for terminology and jargon. To assist you with the content ahead we ve prepared a short Glossary of Terms specific to reptiles. In addition, the online WildlifeCampus.com website has an interactive free to use Glossary covering over 1,100 terms. Anal Scale Abdominal Anapsid Anterior Anti-venom Aquatic Arboreal Bridge Carapace Cardiotoxin Caudal Chelonian Cloaca Clutch Colubridae Costral Crepuscular Cusp Cytotoxin Diapsid Diurnal Diverticulate lungs Dorsal Anal scale refers to the scale between the last ventral scale and first subcaudal scale. In chelonians it refers to the last plastral scutes. A scute or shield that is in the middle of the chelonian plastron Anapsid skull characterized by having no opening in the temporal region of the skull. Towards the front / at the front A serum produced to aid in the treatment of snake bites. Living in water Mainly living in trees Area in a chelonian where the plastron and carapace join. Refers to the top of the shell of a chelonian A toxin that mainly affects the heart, stops the heart muscles from working. It is a form of neurotoxin. Refers to the tail Refers to tortoises and terrapins Common uro-genital opening. The sexual organs, digestive tract and urinary system all exit through the cloaca. Birds also have cloacas. Quantity of eggs laid by a female. Double clutch will refer to two lots of eggs being laid by a female in a season. of snake that in most cases has fixed teeth to both jaws or weakly developed rear fangs. The majority are harmless. Scutes on a tortoise between the vertebrals and marginals Active at dusk and dawn / sunrise & sunset. Referring to the hook(s) present at the tip of the upper beak of a chelonian. Toxic protein that destroy cells, often leading to necrosis Diapsid skull having two openings in the skull behind each eye. Predominantly active during the day / sunshine Refers to either a division off the main lung or a secondary chamber / sac off the main lung. The upper part of the body

13 Advanced Snakes & Reptiles 13 Dorsal scale Dorsolateral Elapidae Endemic Envenomation Fang Femoral Fossorial Gravid Gular Haemotoxic Hatchling Hemipenes Humeral Intergular Interstitial Skin All the scales to the upper body / all scales excluding the subcaudal and ventral scales. The scales or area to either side and including the backbone or spinal region and above the lateral area. Snake who members are fixed front fanged snakes which is mainly represented by cobra's and most species are Neurotoxic. Only naturally occurring in a specific region. When venom is injected into another body from a reptile or insect Specially modified tooth to carry venom from the venom glad into the prey. Can be grooved or hollow fang. Scutes that are behind the abdominals and in front of the anals. Adapted to underground living. A pregnant reptile A scute that is on the plastron of a tortoise or terrapin below the neck A venom that negatively influences the circulatory / blood system and clotting. Death usually occurs through bleeding to death. Refers to newly born reptile. Paired copulatory organ, which is in male reptiles in the order squamata. Scutes that are behind the gulars and in front of the pectorals A scale that is between the gulars of a terrapin. Skin between the scales which in some species is very visible like the Cape File Snake. Intramuscular Injected / envenomation into the muscles Intravenous Jacobson's Organ Keel Labial Lateral Loreal Marginals Injected / envenomation into a vein Organ situated in the roof of the mouth, used in scent recognition. Scent particles drawn in via the flickering tongue are deposited in the organ, which then translates the information to the brain. A small ridge on each scale. This is most noticeable in viperidae / adder species Usually referring to the upper and lower scales of the lips. Refers to the side of the snake. This is above the ventral scales and below the dorsolateral area. A scale that is between the nasal and preocular scales which is mainly missing in Elapids Scutes around the side of a tortoise or terrapin

14 Advanced Snakes & Reptiles 14 Montane Necrosis Neurotoxic Nocturnal Nuchal Oviparous Ovoviviparous Parietal Pectoral Plastron Posterior Postnasal Postocular Prefrontal Prenasal Preocular Recurve Rhombic Riverine Rostral Scale Scute Shedding Shield Sloughing Areas in mountains Death of tissue in a localised area, normally occurs after bites from Adders, cytotoxic species. Venom that usually affects neuro-muscular function, for example making breathing and movement difficult. This venom is predominantly found in elapids. Usually active at night A scale in chelonians that is between the marginals just above the neck Reptile that lays eggs refers to species that incubate their eggs internally. Their offspring hatch from these internal eggs and then emerge from the cloaca giving the false impression that they give birth to live young. Examples include Puff Adder and Rinkhals Scales that are the last head scales before the dorsal scales start A scute in chelonians that is located behind the Humerals by the front legs Refers to the lower half of the shell Refers to the rear part of the animal / reptile Scale situated behind the nose. Scale situated behind the eye. Scale on top of the head Scale situated to the front of the nose Scale in front of the eye Often refer to the teeth that are curved backwards A diamond shaped (or close to) shaped marking on the body Associated to areas near to rivers Large scale infront of the nose Small, flat hard (usually) parts or structure on the surface of a reptile A keratin plate that covers the bone of a chelonian shell When a snake replaces it's skin with a new skin usually by crawling out of the old skin. Large specimens and other reptiles often slough. Often used as an alternative to scute. When the old skin is replaced with new skin, the old skin usually coming off in bits.

15 Advanced Snakes & Reptiles 15 Subcaudal Supracaudal Supraocular Tenting Terrestrial Tubercle Ventral Vertebral Viviparous Scales that are situated under the tail, behind the anal scale. These may be singular or paired Scute at the back centre of the carapace above the tail. Usually single in tortoises but can also be divided, and usually divided in terrapins. Scale situated above the eye. Usually refers to the carapace scutes that are raised. Where a specimen mainly lives on the ground A enlarged scale. Present in some tortoises to either side of the tail or to the side of some chameleon species. Refers to scales on the underside of the reptile, which in snakes are the large scales that the specimen crawls on. Refers to the scutes that run over the centre of a tortoise on the top. refers to species that give birth to live young