Advanced Snakes & Reptiles 1 Module # 4 Component # 1 Capturing and Handling This is not a snake Capture or Handling course. This course in no way encourages, teaches, trains, supports, persuades or promotes the capture or handling of any species of snake in any manner whatsoever. While we will certainly discuss the expected or anticipated reactions of many snakes species to being captured and handling DO NOT ATTEMPT TO CAPTURE OR HANDLE SNAKES The capture and handling of snakes is the sole domain of the professional and should never to attempted.
Advanced Snakes & Reptiles 2 Serpentes Snakes differ from most terrestrial animals, but specifically from lizards in that they do not have: moveable eyelids limbs external ears Snakes only have one functional lung. In some species the left lung may be totally absent, as opposed to reduced. Some species may have limbs which are now greatly reduced and serve no purpose. Snakes walk on articulated ribs that are connected to a backbone or spine. The "walking" speed is snakes is nearly always over exaggerated. Even very fast moving snakes like the Black Mamba cannot exceed 20km/h, so there is no way it will outrun a horse as is sometimes stated. Most species can be moved away from at a brisk walk or slow jog. In addition with the system reptiles have, the speed is restricted for very short bursts, after which they tire. They have a retractile tongue that is used for smelling by picking up scent particles and placing them in the Jacobson s organ for identification.
Advanced Snakes & Reptiles 3 Locomotion Snakes move in 4 different ways, which are serpentine, caterpillar-like movement, side-winding and concertina type. 1. Serpentine is the most commonly seen movement of snakes or typical movement of most species. 2. The caterpillar-like movement is often used by large bodies snakes like pythons and large adders. The disadvantage of this method is it is slower than serpentine. 3. Concertina type movement is mainly used in difficult terrain or to get over obstacles. Two variations occur. The first is when a snake puts its' head over an object and pulls the body up from this anchor point. The other variation is when snakes push forward using their tails, which is mainly in underground species. 4. Side-Winding is used by desert species on the dunes or loose ground. This is mainly done to reduce the area of the snake making contact with the hot sand.
Advanced Snakes & Reptiles 4 Classification Snakes are divided up into five main Families based the jaw & teeth / fang types. These are: 1. Typhlopidae teeth to the upper jaw only 2. Leptotyphlopidae teeth to the lower jaw 3. Colubridae teeth to both jaws 4. Elapidae fixed front fang 5. Viperidae hinged front fang The Elapidae and Viperidae families have developed specialised teeth that are hollow or grooved to carry venom from the venom gland. As a rule snakes are carnivorous but there are a few insectivores. Ophdia taxonomists, those systematic zoologists concern with the classification of snakes have surprisingly not been able to complete the classification of the group, even all known species are available for examination. The 8 th Component of this Module deals with un-resolved species and we ll explore which species are affected and why.
Advanced Snakes & Reptiles 5 Venom Types There are three predominant venom types, but most snakes are a mixture of all venom types, however the other parts of the venom are so negligible compared to the predominant they are of little consequence. The indigenous two rear fanged species (the Boomslang and vine / twig snake) of snake are both Haemotoxic. Most Elapids are Neurotoxic and most Adders are Cytotoxic. As always there are exceptions to this rule. Neurotoxic Venom These act on the nervous system in such a way as to block the transmission of nervous impulses to muscles in the body. The result of this is ultimately the paralysis of the respiratory muscles and thus the death of the victim. This venom is found in all the mambas and most of the cobras with the exception of the spitting types. The most common symptoms of neurotoxic envenomation are dizziness, vomiting, sweating, nausea, drooping eyelids, respiratory distress, agitation, salivation and impaired vision. Cytotoxic Venom The effect of these venoms is that of tissue destruction and haemorrhage. The way in which this is caused is still not completely understood, but it is known that death from these bites occurs as a result of hypotensive shock caused by fluid loss at the site of the bite. These venoms are commonly found in the adders and the spitting cobras. Typical signs of envenomation are extreme pain, swelling, haemorrhage, blistering of the skin and necrosis. Haemotoxic Venom This venom is extremely dangerous to man. Bites from these snakes cause massive haemorrhage (rupturing of blood vessels). Death is likely to occur as a result of brain haemorrhage, blood loss and kidney failure. Found only in the Boomslang and the Vine snake. These snakes are not aggressive, however, unlike mambas and some adders. The majority of all snakes are Colubrids that kill via constriction.
Advanced Snakes & Reptiles 6 Characteristics Hearing Snakes are not able to hear as we do as they do not have external ears. They hear via vibrations caused by sound that moves through dense objects such as land, trees, concrete etc... The sensitivity of this organ is high and will often cause them to move away before you get too close to them. Some snakes are aware of your approach but are too lazy or lethargic to move away, for example the Puff Adder. This is why so many hikers get bitten by this species. Sloughing Shedding of the skin (sloughing) is determined by growth rate. They literally crawl out the skin, usually in a single piece that is inside out. Prior to shedding they go into the blue. This is when the snake goes dull and the eyes get a distinct blue tinge. The liquid that is produced between the new and the old skin causes this. The old skin then absorbs this liquid to aid in the ease of shedding. The nose is rubbed against a rough hard object to break the skin on the jaw. They will crawl catching the skin on an object, leaving it behind them, often in one piece. Very large pythons normally shed in pieces. Tails The tails cannot be shed or regenerated and all the sexual organs are typically located in the tail. Males normally have longer more slowly tapering tails than females. This is very obvious in the Viperinae families, particularly the Bitis spp. Pest Control In Southern Africa there are approximately 143 snake species, of which around 25% have fangs. Only 10% of the Southern African species have caused human fatalities. Snakes as a group are formidable predators and serve a great function in rodent control. Species such as the African Rock Python kill cane rats in plantations. Other than large raptors like eagles these rats have relatively few predators in farmlands, thus populations could increase rapidly causing extreme crop damage.
Advanced Snakes & Reptiles 7 Vision A snakes vision is relatively good enabling it to move around obstacles in it's path. However they mainly respond to movement, hence why one should remain still if a snake is close to you. 99% of the time they will not strike at a stationary object that does not resemble their natural prey. The 2 species that are reported to have better vision than other species are the Twig Snake and Boomslang. This might be correlated with their arboreal nature, but are certainly not the only tree-dwelling species. Of the 143 species that occur in Southern Africa this Course includes 70 species. We are placing more emphasis on the species you are likely to encounter in the field and those that are potentially lethal to man.
Advanced Snakes & Reptiles 8 Snake Terminology The following list of terms are more or less specific to the study of snakes, and terms that you will encounter as you progress through this snake specific Module. Dorsal Scales The scales to the top of the body Frontal Large shield to the top of the head between the Supraocular Hemipenes Males have two reproductive sex organs that are l located in the tail. Internasal Scale between the nostrils Keeled Scale Scales have a ridge along the length of each scale, often leading to dull colouration. Labials Upper & lower labials are situated along the mouth Loreal Scale between the Postnasal and Preocular scales Parinatal 2 large shields over the back of the head Postnasal Scale behind the nostril Postocular Scales behind the eye Prefrontal Scale between the Internasal and Frontal. Prenasal Scale in front of the nostril Preocular Scales in front of the eyes Rostral Scale Nose scale Subcaudals Scales from the cloaca to the tail tip. These are paired or singular. Supraocular Scale(s) above the eye Ventral Scales Belly scales that are singular from the head to the cloaca.
Advanced Snakes & Reptiles 9 Snake Scales Below are diagrams indicating the scale names and their locations. For some species this information is imperative to make an accurate identification. Scale counts are diagrammatically indicated so that you know where to count to aid in accurate identification. The accuracy of this method has been questioned, especially for ventral scales, but in 99.9% of the cases, the one scale miscounted will make very little difference. Head scales: Left View Head scales: Dorsal View
Advanced Snakes & Reptiles 10 Head scales: Ventral View Body Scales
Advanced Snakes & Reptiles 11 Tail scales