Editors Note: There are 2 ways to make plastic tubes – casting and extrusion. Cast tubes are optically clear and the best choice for situations where you have to visually inspect the creature. Extruded products have fine lines in them and can distort light. There are 3 common types of see-through plastic tubing: Vinyl/PVC, Acrylic, & Polycarbonate. Acrylic is the only cast product available. Acrylic is about 30 times the strength of glass but polycarbonate is about 100 times that. If you have a big old boa or python you might consider a combination of very wide (4-10″) PVC pipe (like they run water through) and acrylic — drill observation holes along one side and then slide an acrylic tube OVER TOP OF THE HOLES and affix it with duct tape (the dimensional stability of the PVC will contain the creature). Now, you can also drill small holes into the PVC pipe and drop acrylic rod into them which will act as a “stop” giving you time to inspect a portion of the creatures – then, move the stop to the next hole and the snake moves down allowing you to can inspect the next length of it. These little holes may also prove useful when having to inject the creature with a syringe or to take a blood sample.
Rattle snake under control while confined in an acrylic tube.
(Image not part of original article)
3.1.2 Handling snakes
Capture and handling of herptiles is also discussed in the manual, Live Animal Capture and Handling Guidelines for Wild Mammals, Birds, Amphibians, and Reptiles, No. 3 (1997). This manual is required reading for anyone who will be capturing or handling live snakes.
The handling of snakes must be kept to a minimum as some investigators have demonstrated a negative impact on snake populations resulting from their study. If snakes do not need to be handled to meet inventory objectives then they should be left alone. Where it is necessary, non-venomous species are best captured by hand, although a snake hook may be used for the larger animals (i.e., Pituophis). When capturing snakes, avoid harmful practices such as pinning the animal down with a snake hook or any other device. Snake tongs should not be used for the capture of non-venomous species nor are they generally recommended for the capture of venomous species. Both tongs and nooses can easily injure snakes if used improperly.
Each snake has a unique and somewhat species-specific responses to encounters with people. Racers will typically flee whereas Gopher snakes will present a threatening display; these behaviours make predicting a snake’s movement easier and thus increase capture success. Once a snake is captured it should be restrained as little as possible. Some species are quite passive and easy to handle whereas others will thrash and bite. For snakes that need restraint, it is best to hold the snake behind the head with one hand while supporting the body with the other. Often it is best to put frantic or aggressive animals directly into a cloth bag until they calm. Snake bags are very useful when dealing with large aggressive animals and for transporting snakes in the field. They are typically fashioned much the same as pillow cases, however, using an actual pillow case is not recommended as they tend to have inadequate reinforcement and stitching in the corners. Once a snake is placed in the bag, the top must be tied securely. Caution must be taken to make sure the snake’s body does not become tied in the knot. The bag in best tied by first twisting the open end and then tying a tight over-hand knot in the twisted material. Snakes are often quite calm once in a bag and can be left for several hours; however, snakes should not be left unattended as they will free themselves from apparently inescapable places. If snakes are to be removed from a site, they will need to be double bagged, or, ideally, placed in bags and then into secure containers.
A snake hook should be used to capture and handle rattlesnakes, but it should not be used to pin the snake down as this will likely hurt the animal. In rocky areas, it may be necessary to use tongs to get hold of snakes, but extreme caution must be exercised to avoid injury to the animal. Once a rattlesnake is captured, it should quickly be transferred to a heavy canvas bag. It then may be measured and marked by inducing it to crawl into a clear cast acrylic tube. Generally, placing the tube over the head of the snake will cause it to crawl up the tube. The snake can then be immobilized by grasping the posterior half of its body and the tube in one hand. The tube should be of a diameter that prevents the snake from turning around once inside (Murphy 1971). The safest way to measure the mass of a rattlesnake is to weigh it inside the canvas bag and simply subtract the weight of the bag.
The snout-vent length (SVL) of each snake captured should be measured by gently stretching the animal along a meter stick. This is most easily accomplished by grasping the animal at the base of the head with one hand and by grasping the tail of the animal just behind the cloaca with the other hand. The measurement must be taken when the snake relaxes. Care must be taken to avoid injury to the snake from pulling too hard. The distance measured is from the tip of the snout to the posterior edge of the anal plate. Measurements should be recorded to the nearest 5 mm. Consistent measurements of snakes are important but become more difficult to attain when measuring the larger species (e.g. Pituophis). Practice measuring snakes is necessary and repeated measurements should be conducted on a series of specimens to assess precision.
The total length of the animals may also be recorded (i.e. from the snout to the tip of the tail); however, this is not as useful of a measure as SVL because many snakes are missing the tips of their tails. Snout-vent length is therefore the standard length measurement and most widely accepted.
The mass of snakes can be recorded using an appropriately sized portable scale (e.g. Pesola spring scale). The mass should be recorded to the nearest gram if possible.
The sex of snakes can be determined using several methods. In most species the base of the tail is noticeably broader in males. This is due to the presence of the retracted hemipenes in this portion of the tail. However, in some individuals this is not readily apparent. These animals should be sexed using a blunt probe of appropriate size (Schaefer 1934). This procedure should be performed only by persons that have some experience with this technique. The probe is inserted caudally, at the lateral margins, into the cloacal opening of the animal. In a male snake, the hemipenal pockets will allow the probe to move caudally for some distance; in a female snake, the probe will not be able to move far. Great care must be taken when using this method as the tissues in this region are easily punctured. Another method used to sex snakes is that of hemipenal eversion. By applying pressure to the base of the tail it is often possible to evert the hemipenes of male snakes. This method is preferred for sexing small snakes and neonates (Gregory 1983) as large males are difficult to evert and excess pressure may cause injury.
The reproductive condition of female snakes should be determined using palpation. By palpating the abdomen of the snake ovarian follicles and uterine eggs can be felt and often counted, although caution must be exercised to avoid injuring the embryos.
Ferner (1979) reviews marking techniques for snakes. Where it is required for long term studies, the recommended method is clipping of ventral or subcaudal scales in a unique pattern for each individual (Blanchard and Finster 1933). Clipping of subcaudal scales is preferable, as there is less risk of injury to the snake from penetration into the abdominal cavity. The entire scale, through the dermis (the underlying muscle should be exposed), should be excised with a small pair of scissors. Similar marks may also be obtained by branding snakes (using a soldering iron) on their subcaudal scales.
Scale #1 is designated as the first scale behind the cloaca to contact its counterpart on the opposite side; this first scale is never clipped. Some combination of scales 2-20 on the (snake’s) left and/or right side are clipped, and the pattern recorded. One recording method uses the following descriptor: “(# of clipped scale on left)L (# of clipped scale on right)R”. An example clipping pattern is therefore 2L2R; in this case, the second scale has been clipped on both the left and right side. When all possible combinations of one and two clipped scales have been exhausted, the series may be expanded to include three or more clips.
There are some considerations to make when marking by clipping scales is applied. Counting scales to read marks is time consuming, increasingly so as more posterior scales are clipped. Similarly, the probability of making an error in counting also increases with higher counts. Limiting clips to the anterior subcaudals (2-10) should provide a sufficient number of marks for most purposes. Some species, such as racers and garter snakes, frequently lose the tips of their tails; for these snakes, scales should not be clipped past #15. Clipped scales may slowly regenerate, and marks may become hard to read over time; in long-term studies it may become necessary to reclip scales as snakes are recaptured. Finally, it is important to consider that this system is used in several B.C. locations, so consultation between researchers is necessary to avoid confusion through duplicate marks, and researchers working together on the same population must agree on the same marking conventions (e.g. which scale is considered #1).
An alternative, but more expensive method, for marking snakes in long term studies, is the use of passive integrated transponder (PIT) tags. These small (10.0 X 2.1 mm; 0.05 g) tags are injected into the abdominal cavity of the animal with a large-bore modified hypodermic syringe. PIT tags are glass-encased electromagnetic coils and microchips, each encoded with a unique alphanumeric code that is read by generating a low-frequency electromagnetic signal with an external reader. The expected longevity of the tags is 15-20 years. The primary advantage of PIT tags is that they cannot be misread (they fail rarely); the primary disadvantage is price (reader: US$950; tags: US$4.75-6.00 each) (Germano and Williams 1993).
Many studies will be short term and will not require “permanent” marks. An alternative method, used for rattlesnakes, is to mark the basal (most anterior) segment of the rattle with paint or some form of tag (Fitch 1987). Paint may also be used on other species, but these marks are temporary as the paint is shed with the skin. Permanent marks (such as scale clipping and PIT tags) should be used only for studies in which a snake population will be visited over more than one season. This will minimize the impact on animals and avoid confusion among studies.
A minimum amount of habitat data must be collected for each survey type. The type and amount of data collected will depend on the scale of the survey, the nature of the focal species, and the objectives of the inventory. As most, provincially-funded wildlife inventory projects deal with terrestrially-based wildlife, the terrestrial Ecosystem Field Form developed jointly by MOF and MELP (1995) will be used. However, under certain circumstances, this may be inappropriate and other RIC-approved standards for ecosystem description may be used. For a generic but useful description of approaches to habitat data collection in association with wildlife inventory, consult the introductory manual, Species Inventory Fundamentals (No.1).
The most productive locations for finding large numbers of snakes are den sites. In temperate climates, snakes must hibernate during the winter months (Gregory 1982; Macartney et al. 1989). These hibernating sites are often referred to as dens. It is thought that the locations of suitable denning sites is limited in some areas and that snakes consistently aggregate at the few available sites. Both in the spring and fall, large aggregations of snakes may be found near dens, which may also serve as important basking sites for some species. These aggregations of snakes may be made up of several species (e.g. Coluber constrictor, Pituophis catenifer, Thamnophis sirtalis, and Crotalus viridis in Okanagan valley den sites).
“Chance encounter ” is likely the most common way to find den sites. One can greatly increase the chance of encounter by keeping in mind the general characteristics of den sites. Dens are commonly found on south facing rock outcrops. These may be in the form of talus slopes, solid rock faces that contain deep anastomosing fissures or even human-made structures such as road embankments constructed from piled cobbles. Den sites are often overlain by a top layer of soil, but the underlying rock fissures provide access for snakes to depths below the frost line.
Surveyors should be aware that there are detrimental impacts associated with using den sites as sampling areas. It has been suggested that repeat visits to dens by researchers alter the behaviour of snakes in the vicinity of the den (W.S. Brown, pers. comm.). If true, this will undoubtedly affect subsequent samples but, more importantly, repeated visits may disturb the snakes’ natural activity patterns and possibly cause a reduction in snake numbers. Repeated visits to denning sites may also damage the site itself through compression of the substrate and shifting of rocks due to human traffic. When visiting den sites natural cover objects should not be disturbed and the researcher should step carefully on solid ground that will not shift underfoot. It is also important to be quiet and may be advantageous to view the den location from a distance. Because of the potential risks to the focal species, repeated sampling at den sites is strongly discouraged.
Several other problems are associated with sampling at dens. Perhaps most fundamental of these is a lack of knowledge as to whether all species of snakes have the same denning requirements or whether only certain species den in aggregations. Also, different groups within a population may utilize different denning habitats. For example, young garter snakes are frequently absent from den samples that contain adults (Gregory 1982, 1984). Known locations of den sites are limited in the province. When den sites are encountered they should be recorded and the details of the location sent to the Conservation Data Centre.
Manufacturer: Animal Capture Equipment, IncWeight: 9.00 lbs
Tube-Em™ snake tubes may be the last set of snake tubes you’ll have to buy.These are quality tubes requested by zoo professionals and leaders in the herp field.
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You’re going to need a VERY BIG pipe for this one, though…
A python sits on a road after swallowing a pregnant ewe in the village of Kampung Jabor, about 200 km (124 miles) east of Kuala Lumpur, on September 5, 2006. The six-metre reptile weighing 90 kg (198.5 lbs) was too laden to move, making it easy for firemen to capture it, said a local daily newspaper. Picture taken September 5, 2006. [Reuters]