Another location at which to encounter potentially large numbers of snakes is at a nesting site. Several oviparous species are known to be communal nesters and often migrate from their summer range to nesting sites (Parker and Brown 1980). The nesting site not only provides an opportunity to capture gravid female snakes, but also to capture hatchling snakes, a component of the population that is often not adequately sampled once it disperses from the nesting site. Although gravid viviparous species do not have nest sites, they do have behaviours that make them more susceptible to capture. For example, they often bask in specific locations (Macartney 1985). Gravid rattlesnakes do not disperse far from the winter den, but move to basking sites (maternity sites) near the den where they will spend the summer until parturition (Macartney 1985). Known locations of nest sites are limited in the province. When nest sites are encountered they should be recorded and the details of the location sent to the Conservation Data Centre.
If a researcher cannot find a snake den or nesting site by searching, a snake may be used to lead the researcher to the den/nest site. Snakes caught in the field can be equipped with miniature transmitters and followed to critical habitats. Anyone undertaking radiotelemetry work should be familiar with the manual, Wildlife Radio-telemetry, No. 5 (In prep. for RIC committee).
Radio transmitters are small (2-20 g or larger) devices that broadcast a radio signal on a unique frequency (some transmitters also have components that encode the temperature of the transmitter into the signal). Some workers have force-fed transmitters to animals; these transmitters are often regurgitated or passed through the gut and have been found to modify the behaviour of the animals (Lutterschmidt and Reinert 1990). For this reason, force-feeding is discouraged in favour of surgical implantation. Transmitters are implanted subcutaneously or into the abdominal cavity (Reinert and Cundal 1982). Reinert (1992) provides a useful review of radiotelemetry methods.
Radiotelemetric studies are currently appropriate only for larger snakes; the implanted transmitter should be no more than 5% of the body weight of the animal (e.g. 2 g transmitter in a 40 g snake). Implanted transmitters may affect the behaviour of the animal, including feeding rate, preferred body temperature, activity level, and locomotion (Fitch 1987). The surgery itself may have a significant effect on the health and condition of the animal, and all subjects should be retained for several days to allow the animal to begin to heal. Other drawbacks of radiotelemetric methods include expense (receiver: $1000-1200; transmitters: $150-300) and potential technical problems (bad batteries, penetration of coelomic fluid into transmitters, poor electrical connections, and short reception/transmission distance, especially with small transmitters and snakes that hide underground) (Peterson et al. 1993). Thus, radio-telemetry studies should be well planned, thoroughly reviewed, and only commence after careful consideration of other options.
Voucher specimens serve to document the identity of organisms encountered or used in any study. They are the only method for validating the presence of a species in a study and for making historical comparisons. Voucher specimens can improve the credibility of an inventory or monitoring project and should be collected when appropriate. If the animal can not be collected because it is rare, endangered, or protected by law, for example, then a series of good photographs should be taken. When an animal is sacrificed, the voucher specimen must be preserved properly, documented with the appropriate field data and deposited in a museum or other institution where they are readily accessible. Detailed protocols for collecting voucher specimens of snakes can be found in the manual, Voucher specimen collection, preparation, identification and storage, No. 4 (In prep. for Resources Inventory Committee).
If snakes are to be killed, it must be done humanely (see also Live Animal Capture and Handling Guidelines for Wild Mammals, Birds, Amphibians, and Reptiles, No. 3). The preferred method is lethal injection with Nembutal (pantobarbital) (Pisani 1973). A 1.0 ml injection of commercial Nembutal (1 g/ml) in the heart of a large reptile should be sufficient to produce rapid death. Use a 1:10 dilution for smaller specimens. Nembutal is a restricted drug and is not used much except by professional collectors. Placing specimens in a freezer is an alternative method, but may cause distortion of cells and tissues.
The preservation of snakes is conducted in two steps. The animals are first preserved in a fixative and later transferred to alcohol for storage. Fixation of snakes is done with a 10% formalin solution. To make this, the commonly available stock solution (37-40% formaldehyde, which is synonymous with 100% formalin) is diluted one part full strength stock solution to nine parts water, resulting in a 10% formalin solution. Care should be taken to avoid inhalation of formalin fumes. The specimen should be injected with a hypodermic syringe every 10 cm along the body so that the entire body cavity is filled with fixative. The tail portion of the animal should also be injected in several locations. Male snakes should be injected at the caudal end of the hemipenal pockets, making the hemipenes evert. If a hypodermic needle is not available then the specimen should have several incisions made in the ventral body wall so that the formalin can readily penetrate the tissue. A waterproof label with the proper collecting information should be tied around the neck of the animal with a square knot. The specimen should be coiled (and possibly tied with string) in a position that facilitates storage. The fixation process will make the specimen rigid, so positioning must be considered carefully. After injection, the specimen should be soaked in a 10% formalin solution for at least a week, but a period of several months is better. Later the specimen can be transferred to a 70 % ethyl alcohol solution for permanent storage, but should first be soaked in water for 24 hours to prevent dehydration (Pisani 1973).
Snake surveys follow a sample design hierarchy which is structured similarly to all RIC standards for species inventory. Figure 3 clarifies certain terminology used within this manual (also found in the glossary), and illustrates the appropriate conceptual framework for a presence/not detected survey for snakes. A survey set up following this design will lend itself well to standard methods and RIC data forms.
Figure 1. Survey design hierarchy for snake surveys. Example shows study areas and search units within them.
· When working in areas with rattlesnakes, all members should have experience handling venomous snakes and knowledge of first aid for snakebites; nearby hospitals should be notified of the possibility of a snake-related medical emergency so that they are prepared to provide treatment if necessary.
A core of equipment will generally be required for any survey in which snakes are captured:
The table below outlines the type of surveys that are used for inventorying snakes for the various survey intensities. These survey methods have been recommended by wildlife biologists and approved by the Resources Inventory Committee.
Table 2. Types of inventory surveys, the data forms needed, and the level of intensity of the survey.
| Survey Type | Forms Needed | *Intensity |
| Hand Collecting |
|
|
| Road Survey |
|
|
| Trapping |
|
|
| Time-constrained Search (TCS) |
|
|
| Quadrat Search |
|
|
| Transect Search |
|
|
| Mark-Resight |
|
* PN = presence/not detected (possible); RA = relative abundance; AA = absolute abundance
